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Service Manual for the PR155B MF/HF

1. CES CA hi3 sz Modifications Fig 24 S Alva 41516 7 819 12 7 15 1 15 1715 15191 15 FIG24B A 6 C DECAY SHAPER CIRCUIT amp BOARD LAYOUT
2. Transformer 406 8 08225 012 LI L2 13 14 RF Choke miniature 10004H 10 406 4 98012 005 VT1 VT2 Transistor 28512 BSY95A ST95A 411 4 98138 VT3 Transistor 283030 Texas Insts 411 4 98136 VT4 VT9 Transistor BCY70 417 4 98267 001 RV1 Potentiometer 10k ohms 404 1 00405 009 RV2 Potentiometer 2 5k ohms 404 1 00405 004 D1 D3 D4 D5 D6 D8 D9 Diode IN4148 415 4 98393 D2 Diode Zener 8 2 415 4 98161 006 D7 Diode Zener 3 3v 415 4 98167 007 PR 155 51 Issue T 5 13 Module 9 5 13 1 Unit 9A Resistors 0014 os o Capacitors Miscellaneous Circuit Ref VTi vn VTA VIS D1 D2 RV1 RV2 Tssue 6 630 1 14119 630 1 14188 Rating Watts AE Electrolytic Electrolytic Polystyrene Electrolytic Electrolytic Mullard C280 Synthetic Resin Transistor 28512 BSY95A STY5A Transistor ASY26 S T C Transistor 2N1507 Texas Insts Diode 04200 Mullard 100k ohms 1k ohms Potentiometer Potentiometer 403 4 18168 111 403 4 19168 141 403 4 19168 051 3 403 4 78168 07 403 4 18168 151 4 18168 081 403 403 4 78168 001 402 1 28009 024 402 1 01201 001 400 4 98179 012 402 1 01291 001 402 1 01200 015 400 4 98268 007 424 4 98042 192 NEN X 417 4 98138 417 4 98039 001 417 4 98139 415 4 98011 404 1 00405 006 4
3. 63e 1 14020 Modifications Fig 9 Issue 4 121315151 5178151112 FIG 9 INTERPOLATING OSCILLATOR CIRCUIT AND BOARD LAYOUT FIG 9 INT OSC SPECTRUM 9 SKT 05 Re 120 15 V 02 7 OV T R2 c2 R7 D2 893 8 esd 27 C6 TO WAFER F2 R9 C LOCK d Las Fra pre 47 c ca d T 47p 10 vds B vri 2 RI vTt T2 BSY9SA BSY95A BSY95A 22 Jee ead li v Ter iunc c SE TO WAFER FI 3 2 WAFER FI WAFER Fa 4 CONTACT 630 DA 14300 RV4 R4 R3 Rv2 R2 RVI RI 3 5 9 i3 17 21 25 27 29 1 2 4 8 12 16 20 24 26 28 Sc FI 18 19 23 d 6 10 18 22 TO D C AMP 5 39 L3 FI F2 pum pu re RIO 1 2K WAFER E CIRCUIT WAFER FL amp F2 Turret Mod No 4 2 Embodied See Fig l For Overall Mod State Fig l For Overall Mod State FIG IO TURRET FIG IO MC S SELECTOR TURRET COMPARTMENT 2 CIRCUIT AND BOARD LAYOUT COMP 2 824 470 ale Se 5 v R23 20 829 82 DWG 630 DA 14195 R26 aue d BOARD See Fig For Overall Mod State FIG PRI55 PHASE SPLITTERS AND MODULATOR BOARD 6 CIRCUIT AND LAYOUT FREE FROM TURRET 15 63 V 35 qe 5
4. Si Crk 398 5 047 DWG NO 650 0A 14938 216 16 14 5 wild ORE RT Py S2208 SISK a 6 avi 1 R33 E 4 OLS 3 2 LSB 456 15 15 IO 6 10 8 MHz X RIO 63 b CIRCUITO DIAGRAM GENERATOR MODULE 10 MKI Rae 106 5 1895 gt vTi2 vis 0 29 T COMPONENT 52 4640 FIG 6 Ed O 5 100KC TO IOOKC S OUTPUT 19 Ge 5 4 43 ANPUT 047 KCIS AMP 81 Su SKT i 75 gt 1000 100 PL BOARD A BOARD B BOARD 7 DWG 639 4777 BOARD7A 4 3 4 5 6 FIG 17 PR 155 F AMPLIFIER AND DETECTOR MODULE 7 CIRCUIT AND BOARD LAYOUT FIG 7 MODULE 7 12 1000pH 4 000 47 21 1060 H 2 000 O 5v JOOKHz IN PL 18 T Berro La 1000uH AGC ouT ad i f i zi 5 T En E 10K IF GAIN amp AGC RI 22K 560 2 2 1750 FIG 18 PRISS A G C AMPLIFIER AND DETECTOR MODULE 8 CIRCUIT AND BOARD LAYOUT FIS 5 3 ER 15 COMTROL 5 26 4 m QUDSPEAKEA j Ker vrs 44 5 25
5. also feeds emitter follower which provides an output to the 10 6 10 8 MHz generator module 11 The spectrum output from board is injected at the emitter of the first of two transistors in 48 MHz selector circuit on board B The collector circuit of VT1 is tuned to 48 MHz by L1 and coupled to VT2 base The feedback capacitor C2 improves the Q of the circuit such that it would oscillate freely at very nearly 48 MHz thus the 48 MHz of the input signal is amplified and reproduced relatively free of all unwanted frequencies at VT2 emitter From 2 the 48 MHz output is filtered in L2 tuned to 48 MHz C4 and C5 and applied via VI3 an emitter follower to further selector circuit in module 4 The d c supply to VI1 and VT3 is locally stabilised at 10V zener diode D2 The 15V d c supplied to the spectrum generator and the 48 MHz selector circuits are each independently filtered in filter circuits contained on board B 1 MHz oscillator circuit is also incorporated in this module but is not used in this application 1 is disabled by setting the link on the rear panel of the receiver to INT 1 MHz OFF 3 6 INTERPOLATION OSCILLATOR Fig 9 The interpolating oscillator provides an output which is mixed with the selected output from module 10 to make up the first local oscillator frequency in order to control the first local oscillator at this frequency It is tunable over the range 2 2 MHz to 3 4 MHz and the tuning i
6. 16 22 403 4 18168 113 8 Erie 16 403 4 18168 065 9 ES Erie 16 403 4 78168 039 1 Erie 16 403 4 18168 109 1 1 Erie 15 403 4 18251 161 Issue 9 38 PR 155 Capacitors Value Tol V Wkgs Maker and Type uF 2 Part No 400 4 98308 104 27p Erie 40 5pf Erie NPO Geramic 400 4 98425 054 5 Polystyrene 400 4 98119 016 Erie NPO AD Cerami 400 4 98425 089 Erie NPO AD 400 4 98425 087 Polystyrene 400 4 98119 026 Mullard C250 400 4 98268 007 Miscellaneous Circuit Ref Description Diode 11 145 415 4 98393 Diode Zener i J 5 415 4 98167 003 VT2 VT3 Transistor FS 95A 28512 T95A 417 4 98138 5 5 4 Wafer Assembly E 630 1 4 0 Circuit Ref scr pt on Rerici 120 nims 10 iw Erie 16 403 4 78168 061 2 3 Res v 150 ohes 10 lw Erie 16 403 4 76168 065 RV1 tes 1 57 ohms 403 1 00405 069 RV2 RV3 otirometer Ik ohm 403 1 00405 005 52545 Wafer Assembly F1 F2 650 1 11281 Description 406 8 0832 L1 5 131 Inductor 14 turns L2 132 Inductor Acsembly 14 turns 406 8 08324 002 L3 133 Ind tor Assembly 13 turns 406 8 08325 003 L4 134 inductor Asrembly 13 turns 406 8 08324 003 15 1 16 137 Indu tor Assembiy 12 turns 406 8 08325 004 L6 136 Indu tor Assembly 12 turns 406 8 08324 004 L8 L10 Tz 138 140 142
7. tuned frequency produce an intermodulation product at the tuned frequency equivalent to wanted signal reference level 100V to 1257 or 2007 48 to 520 Hz single phase or 24V d c floating supply or positive earth Power consumption 22W at 24V d c approx Operation 2090 to 50 95 Storage 40 C to 70 C 95 Width Suitable for rack mounting Height T in Depth 17 in Weight 38 lbs nob Issue 1 5 on MEGAHERTZ a KILOHERTZ EFEZ 1 RECEIVER PPS OME Deo bib BANDWIDTH RENE GAIN an i MEGAHERTZ STAND AY EOM B 7 1508 EERIE BURG FEEL FIER CLUE A P p AXE 5 Renters gt PR155 Communications Receiver Issue 5 6 PR155 1 INTRODUCTION 1 1 GENERAL The PR155B Receiver is an all transistor receiver designed for the reception of AM CW MCW DSB SSB or FSK signals in the frequency range 15kHz to 30MHz Facilities can be provided to receiver other types of transmission if required The receiver is of modular construction and is contained in metal case which may be fitted with feet for desk use or with brackets for mounting in gtandard 19 inch rack or cabinet assembly Brackets and feed are provided with the equipment together with the re
8. 1 in a Hartley type circuit Tuning of the oscillator is effected by the preset capacitor C5 and the varactor diodes D1 and D2 in conjunction with the saturable reactor L1 The reactor current is controlled by the d c amplifier in the phase lock loop circuit 3 8 to provide amp coarse adjustment of oscillator frequency and finer faster adjustment is provided by 01 and D2 under similar control Issue 6 16 155 The oscillator output is coupled via C4 to emitter follower VT2 which provides drive to two further emitter followers and VT provides an output to the phase lock loop circuits and VT4 to the first mixer 5 5 SPECTRUM GENERATOR MODULE 10 MKII Fig 8 This module contains a spectrum generator generating signals at 1 MHz intervals in the spectrum 35 MHz to 64 MHz and a 48 MHz selector circuit which selects the 48 MHz output from the spectrum generator for use at the second stage of frequency conversion 1 MHz signal normally taken from the associated PR1553 Receiver is applied to VT3 base It is amplified in VT3 and VT5 stages but the output from VT5 is differentiated to produce harmonics at each 1 MHz interval through out the spectrum 35 MHz to 64 MHz These harmonics are coupled via emitter follower VT6 to the 48 MHz selector board B and to another emitter follower VT8 which provides the spectrum output to compartment 2 of the turret assembly 3 7 via the high pass filter C20 L1 C21
9. 12 17 10k 10 13 68k 10 i Erie 16 403 4 18168 195 15 25 3 9k 10 Erie 16 403 4 18168 133 18 4 10 Erie 16 403 4 18168 185 20 33 10 i Erie 16 403 4 18168 029 21 680 10 16 403 4 78168 097 26 180 10 i Erie 16 403 4 78168 069 27 1 5k 10 0 1 Erie 15 403 4 18251 112 28 560 10 i Erie 16 403 4 78168 093 46 220 10 i Erie 16 403 4 18168 013 41 330 10 Erie 16 403 4 18168 081 48 9 w 10 lt Erie 16 403 4 18168 033 22 180 ao 1 Erie 15 403 4 78257 161 Capacitors Maker and Type 1 2 5 8 9 13 14 39 4 641511 15 Mullard C280 400 4 98268 005 16 20 35 36 Mullard C280 400 4 98268 007 7 38 10 Mullard 295 400 4 98245 006 12 40 150 Plessey y 439 1 10171 091 Electrolytic 18 Mullard C295A 400 4 98245 003 19 20 Electrolytic 402 8 50833 029 Miscellaneous RV1 Potentiometer 10k ohms 20 404 1 00405 009 11 L2 13 L4 RF Choke miniature 1000pH 10 406 4 98012 005 1 7 5 VT10 Transistor 25512 BSY95A ST95A 417 4 98138 22 Diode IN4148 415 4 98393 D3 Zener diode 4 7 5 415 4 98167 001 PR 155 49 Issue 5 11 5 Unit 78 630 1 17774 Value Rating 10 16 Resistors 30 314 35 32 33 43 42 403 4 18168 117 403 4 18168 153 403 4 18168 105 403 4 78168 125 403 4 78168 073 403 4 78168 089 403 4 18168 181 403 4 78168 161 403 4 78168 137 403 4
10. 4 98145 VT2 VT4 Transistor 25512 Texas insts 411 4 98138 PR155 41 Issue 5 5 8 Compartment 3 board J 630 1 14109 Resistors Tol Rating ohms Watts i Metal oxide 403 4 18148 01 i Metal oxide 403 4 781 48 131 i Erie 16 403 4 18168 145 i Erie 16 403 4 18168 089 i Metal oxide 403 4 181 48 014 i Erie 16 403 1 18168 105 i Erie 16 403 4 18168 153 ES Erie 16 403 4 18168 065 i Erie 16 403 4 18168 081 i Erie 16 403 4 18168 101 i Erie 16 403 4 18168 131 i Erie 16 402 4 18168 185 1 Erie 16 403 4 78168 073 Value Tol V Wke Maker and Type Part No uF 0 1 20 250 Mullard 0280 400 4 98268 007 15 10 20 Plessey Electrolytic 402 1 50832 070 25 25 Plessey Electrolytio 402 1 01200 015 041 20 250 Mullard C280 400 4 98268 005 1 Potentiometer 250 ohms 404 8 00405 008 RV2 Potentiometer 5k ohms 404 8 00405 024 RV3 Potentiometer 1 5k ohms 404 8 00405 069 RV4 Potentiometer 25k 404 8 00405 023 D1 Diode Zener 10V 5 415 4 98167 003 1 4 VT8 VT9 Transistor 28512 BSY95A 5195 417 4 98138 VT5 VT Transistor 253030 Texas Insts 411 4 98136 VTT Transistor 2N1507 Texas Insts 411 4 98139 Issue 7 42 PR155 5 6 Module 1 RF Amplifier 630 1 17670 Resistors Rating Watts 403 4 78229 154 403 4 78168 001 403 4 78168 033 403 4 18168 101 403 4 18168 145 403 4
11. 8341 C20 Rao TO BOARD H Ka d R m NTERP OSC IN Cac FIGH TURRET BOARD G LO IN vT BSY 954 FROM o BOARD G R4 8 RS fiR2 83 335 8 b b Wa 05 gi TW R2 WG 7 16 08107 FROM BOARD G FROM BOARD J TO BOARD Y PINK No 30 Moditications 19 12 Issue 8 A Turret FIG TURRET Embodied See Fig I For Overall Mod State FIG 12 PRISS PHASE DETECTOR BOARD CIRCUIT AND LAYOUT AMAD H R2 t30 FROM PHASE DETECTOR Cr 9 TE B Y YO PHASE DETECTOR O A16 AY 5 19 95 P PT 15 R20 5 RIT 25 a as 47 2 REACTOR CONTROL Dws NO 99 ORANGE GREEN CONTROL 5 ORANGE BOARD H PINK ES er FROM BOARD R9 s B in AV3 res lt a p y en R2 RIS RI2 as Gn Lj gt R2 db Eb DwG 6307 4109 5 3 RRET FIG 13 PRISS D C AMPLIFIER AND REACTOR SWEEP GENERATOR BOARD J CIRCUIT AND LAYOUT ESG
12. Mullard 0286 4 98268 001 Ceramic Miscellaneous Inductor 9T 406 8 08324 006 F1 F2 min feed thro Ceramicon Erie 400 4 98266 CFT 3000 FLA Orystal Filter 10 7 MHz 428 4 98065 VIS VT6 VTT Transistor 28512 411 4 98016 5 10 Module 5 630 1 17760 Resistors 4 2 5 403 4 78168 053 403 4 78168 089 403 4 78168 161 403 4 78168 153 403 4 18168 105 403 4 18168 137 3 4 15 18 24 26 6 30 T 14 17 19 22 23 25 ep PR 155 47 Issue 0 403 4 78108 093 403 4 78168 113 403 4 78168 049 403 4 78168 057 4 i 4 i 4 i 4 ut nee 20 Erie NPO 911 400 4 98268 00 3 Erie NPO 911 400 4 98268 007 400 4 98119 010 400 4 98260 007 Polystyrene Ceramicon Miscellaneous Circuit Ref Description 1 Transistor GM378 Texas Insts 411 4 98131 net Transistor 28512 BSY95A ST95A 411 4 98138 D1 D2 Diode IN4148 415 4 98393 F1 F2 F3 F4 UHF min feed thro Ceramicon Erie 400 4 98266 CFT 3000 Board Component Unit 5 630 1 17761 L1 RF Choke 1000mH 406 4 98012 005 5 11 Module 7 630 1 17775 5 11 1 Unit 630 1 17771 Resistors Rating Watts 403 4 78184 052 403 4 18168 105 403 4 18168 113 403 4 18168 203 403 4 18168 089 403 4 78168 137 403 4 78168 113 403 4 78168 057 9 14 29 3 4 5 10 24 6 7 19 2 11 16 23 Are Issue 7 48 PR 155 Erie 16 403 4 78168 153
13. With no input to the receiver switch the MODE to CW and set the BFO knob to zero on the scale zero beat is not possible in this position adjust 11 on the BFO sub unit to obtain it The unit side cover must be removed to gain access 4 11 OSCILLATORS a fault is suspected in either the 1 MHz oscillator in module 10 or the interpolating oscillator it can be verified by substituting the suspect oscillator with suitable external oscillators as detailed in 2 2 2 The activity of other oscillators should be verified as detailed in the following paragraphs 4 14 1 First local oscillator module 3 Test the first local oscillator as follows Set the INT 1 MHz and INT VFO links on the rear panel of the receiver to OFF the connections to pins 2 and 3 of module 3 b Break cable 8 and terminate the cable from module 3 with 75 ohm resistive load Connect valve voltmeter across the load The meter Should indicate approximately 625mV r m s Reconnect cable 8 Issue 5 30 PR155 Repeat b at cable 9 similar reading should be obtained d With the load and meter still connected at cable 9 break cable 8 and measure on a frequency counter the frequency of the RF output at cable 8 termination It should be not more than 37 000 MHz e Set the internal oscillator links on the rear panel to ON Reconnect pins 2 and 3 of module 3 Set the MEGAHERTZ control to indicate 1 MHz on the
14. lt f i vig BOARD E 6 4 3 2 1 nom DETECTORS 5 BOARD B UC me 62 4064 DWG NO 630 5 9 5 FIG 19 PRI55 AUDIO AMPLIFIERS MODULE 9 CIRCUIT AND BOARD LAYOUT 19 MOF in R23 L3 SOU 5 SSB ba R2 4 T LSK 181416 i 15 CAL c2 Hz IN ze PL 28 I MLI SN74 ON CX IGO K Hz J SKT 2i O SKT 23 CAL OUT Ed s VT3 SKT 22 7 857 95A Ae c9 i 8201 tso Sk RI8 D3 R20 821 47 NIMB ICK 82 FIG 20 kc s DIVIDER AND CALIBRATE CIRCUIT MODULE 12 CIRCUIT AND BOARD LAYOUT FIG 20 MODULE 12 BSY95A R2 EY u 15K 220 630 DA 23304 2 3141516 7181 ohojufrz c3 wan c9 10 420p FIG 2i R R7 270 cs 4 vT2 BSY95A C6 270 1 B F O CIRCUIT AND L2 10004H 57 000 R9 12 FIRED 20 TO S2 4 630 1 23306 FIG 2i LAYOUT PAR FIG 22 ISOLATING AMPLIFIER CIRCUIT DWG 630 DA ies BRI fae DWG 650 04 4608 30 1746 vT2 BELOW DWG NO 63C 4608 Moditications Fig 23 issue kc 23 REGULATOR CIRCUIT AND LAYOUT FIG 23 28 GAIN EA METER SW 4 R8 R7 METER SWAF 9 1M4149 100 ISV o 5 AF oe M 4 o METER SW RF 3
15. turret the outputs the MHz selector and the interpolating oscillator are mixed to obtain an output at the sum of these frequencies and the phase relation between this synthesized signal and the output of the first local oscillator is detected to provide a control voltage to lock the first local oscillator accurately to the required frequency sweep voltage to tune the local oscillator within the range of control of the phase lock circuits is generated in a multivibrator circuit Three boards G H and J axe contained in compartment 5 the circuits contained on each are described in 5 8 2 5 8 5 and 5 8 4 5 8 2 Phase splitt rs and modulator board G Fig 11 The output from the MHz selector 3 7 is applied via a matching net work to the base of VT5 Phase shift networks R23 C15 and R22 013 C14 are connected between emitter and collector of 5 and the component values are such that two outputs differing in phase by 90 degrees are obtained One of these outputs is amplified in VT4 and applied to T2 and the other is amplified in VT6 and applied to T4 The output of the interpolating oscillator is applied to a circuit similar in operation to that of which the MHz selector output is applied This circuit employs VT1 and VI3 and drives 1 and T3 Transformers T1 to and diodes D1 to D8 form two ring modulator circuits whose outputs are connected together via RV1 Due to the 90 degree phase difference between the modulat
16. 1 14117 10 7 MHz Amplifier 3rd Mixer 5 630 1 17760 100 kHz Amplifier Detector 1 630 A ATTT5 AGC Amplifier and Detector 8 630 1 17750 Audio Amplifiers 9 630 1 14119 Spectrum Generator MK II 10 630 1 14930 10 6 10 8 MHz Generator MK II 11 630 1 14938 100 kHz Divider and calibrate 12 630 1 14116 Interpolating Oscillator 630 1 14000 001 Isolating Amplifier 1 Isolating Amplifier 2 2 630 1 14541 001 BFO u 630 1 23304 Turret Assembly 630 1 14300 Regulator Assembly 630 1 14608 Shaper Board 630 1 17869 Meter Amplifier 6350 1 ATT42 The turret assembly has three separate screened compartments containing the RF filter unit MHz selector and phase lock circuits The RF filter and MHz Selector Compartments compartments 1 and 2 consist basically of rotary switch assemblies which are coupled to the MEGAHERTZ control The components of their associated circuits are mounted on boards in the compartments or on the switch assemblies Compartment 3 containing the phase lock circuits is on the under side of the module and contains three printed circuit boards Boards G H and J Issue 1 8 PR155C The interpolating oscillator BFO and isolating Amplifier modules each consist of a screened box containing a printed circuit board Tuning of the BFO is effected by means of amp variable capacitor located inside one end of the module the capacitor spindle protrudes through the front panel as the BFO TUNE C
17. 14 998 MHz at 217 Verify that an audio output of approximately 1 kHz is obtained and that the millivoltmeter reading again falls by not less than 20dB when the input signal is removed f Set BANDWIDTH to 300 Hz and select the CW mode Inject a signal at 15 MHz and a level of 217 Adjust the BFO control to obtain an audio output at approximately 1 kHz Note the output level Remove the input signal the output should fall by not less than 2648 Set BANDWIDTH to 6 kHz and select AM Apply 1 MHz signal at level of 3 8uV modulated to depth of 30 at 1 kHz to the 75 ohm aerial input Adjust AUDIO GAIN for convenient reading on the millivoltmeter and note the reading Remove the modulation from the input signal the output should fall by not less than 1088 AUDIO PERFORMANCE 1 Output levels To measure the audio output levels apply 15 MHz signal at 200 at the 75 ohm aerial socket modulate the input signal with 1 kHz to a depth of 90 and with AGC ON tune the receiver to the input signal then proceed as follows Set the loudspeaker switch to Connect a valve voltmeter between the centre pole of this switch and chassis Set AUDIO GAIN to maximum the valve voltmeter should indicate not less than 2 45V r m s 400mW in 15 ohms Remove the meter b Load each phone jack in turn with 600 ohms and measure the voltage across the load it should be not less than 2 0V r m s 6 7mW in 600 ohms
18. 15V and are separately decoupled to prevent interaction The input to board is from the slider of the AUDIO GAIN control on the main chassis of the receiver it is applied to the base of VT via C1 R1 Negative feedback is applied to base via 03 Two signals are obtained from collector circuit to drive and VT3 the first two transistors in a complementary single ended push pull configuration of which VT4 and VT5 are the output transistors In order to obtain the anti phase signals for application to VIA and VT5 PNP transistor is used for VT2 and NPN for VT5 The correct bias for Class AB operation of the push pull drivers is obtained by adjustment of RV2 while RV1 is adjusted to equalise the supply voltages across the two push pull sections Temperature compensation is provided by D1 and D2 in the collector load of The input to board B is direct from module 7 it is coupled to the base of VT1 via F1 Ci VI1 operates as an amplifier with negative feedback introduced by R5 to provide an output at the slider of preset gain control RV1 to drive the phase splitter VT2 One output from VT2 emitter is coupled via R10 C6 to the base of VI3 and another from the collector of VT2 is coupled via CT to base Transistors VT2 and operate in a single ended Class A push pull circuit to drive the line output transformer T1 on the main chassis via C8 Balance of the output stages is achieved by the set
19. 16 The circuit accepts a spectrum output from the Spectrum Generator module 10 and provides an output at either 10 6 or 10 8 MHz to the third Mixer module 5 The spectrum input is applied to the selector circuit VT1 2 This circuit which is controlled by the LSB USB bias network RV1 C7 R6 D8 C5 via S1BF Selects either 53 MHz for LSB or 54 MHz for USB required frequency is passed via the emitter follower VT3 to divide by five circuit to Issue 1 20 PR155C The divide by five circuit is a ring counter type circuit from which only the output of the last transistor is taken Two and a half input cycles are therefore required to cause bistable 12 13 to change stage and provide one half cycle of output thus five input cycles will be required to provide one complete output cycle The output from VT13 is a square wave at one fifth of the input frequency i e 10 6 or 10 8 MHz The square wave output from VI13 is passed to VT14 15 and C15 in the collector of VT14 form filter centred on 10 7 MHz which will pass 10 6 to 10 8 MHz This circuit also converts the square wave output from 15 to a sine wave suitable for application to the 3rd Mixer module 5 via SKT15 3 12 THIRD IF AMPLIFIER AND DETECTORS MODULE 7 Fig 17 The input circuit of VT1 the first stage of the third IF amplifier includes an AGO controlled diode similar to the input circuits of modules 4 5 9 and 5 but in this case the gain of the
20. 64 MHz at the 29 MHz setting Remove the frequency counter and connect valve voltmeter in its place The meter should indicate not less than 250mV r m s at each setting of the MEGAHERTZ control 4 12 PHASE LOCK CIRCUITS TURRET COMPARTMENT 3 Correct operation of the phase lock circuits should be verified as detailed below a Break cable 7 connecting the turret to the interpolating oscillator Terminate the cable from the oscillator with a 75 ohm resistive load and connect a frequency counter across the load Switch on the PR155 and adjust the KILOHERTZ tuning to obtain a frequency of 2 5 MHz on the counter The control must remain in this position throughout the following tests Switch off remove the counter and load and reconnect cable 7 b Disconnect pin 2 of module 3 and reconnect to pin 2 via 100k ohms resistor Connect the D C input of an oscilloscope between pin 3 and earth Break cable 9 connecting modules 2 and 3 terminate the cable from module 3 with 75 ohm resistive load and connect the frequency counter across the load c Connect oscilloscope between the reactor control lead on board J turret compartment 3 and earth Fig 13 refers San PR 155 Set receiver to 28 MHz Adjust RV3 on board J to give the following waveform on the oscilloscope Diagram a Diagram a e Reset MHz selector to 21 and 22 MHz in turn adjusting RV1 on wafer E turret compartment 2 Fig 10 refers to p
21. 78168 121 403 4 78168 125 403 4 18251 112 403 4 78168 113 403 4 78168 089 403 4 18168 059 403 4 78168 085 403 4 78168 073 403 4 78168 069 403 4 18168 053 403 4 78168 065 403 4 78168 077 403 4 78168 153 403 4 78168 093 403 4 78168 191 403 4 18168 105 403 4 78168 169 403 4 18251 205 403 4 18251 153 la b c d 2 21 St Capacitors Value Tol V Wke 0 1 20 250 Maker and Mullard C280 400 4 98268 007 82p 5 Lemco 1106 S 124 4 98042 129 12 25 Lemco SM 402 4 98009 032 Lemco SM 402 4 98009 039 8 Tantalum 402 4 98022 027 155 43 Issue Miscellaneous L1 L5 L6 17 RF miniature choke 1000 406 4 98012 005 L2 RF miniature choke 150 406 4 98012 004 VT1 Transistor 417 4 di Transistor BSY95A 28512 ST95A 411 4 98138 775 Transistor BCY70 Texas Insts 417 4 98267 001 VT10 Transistor D986 Texas Insts 417 4 98153 D1 D2 D4 Diode FRB126 415 4 98400 D5 Zener Diode 6 81 5 415 4 98161 009 D6 77 Diode 1N4148 415 4 98393 Board Component Unit 1 630 1 17671 D8 Diode RV1 22 4 98214 Potentiometer 5000 205 415 5 7 Module 2 630 1 14111 Capacitors 1 0 Polystyrene 400 4 98263 026 2 L C R Ltd Polystyrene
22. 78168 077 403 4 18168 165 403 4 18168 005 Miniature foil Polystyrene Polystyrene Polystyrene Miniature foil Polystyrene Variable 400 4 98268 005 400 4 98245 010 400 4 98245 001 400 4 98179 027 400 4 98268 007 400 4 98366 018 401 4 98026 003 Description Part 404 1 00405 012 406 8 0832 3 005 406 4 98012 005 117 4 98138 1 23306 Potentiometer 5 oh Inductor Assembly RF Choke miniature 1000uH 10 Transistor BSY95A 5 95 28512 Board Component VT2 PR 155 Issue 8 37 5 4 REGULATOR ASSEMBLY 630 1 14508 Refer to sub section 5 18 5 5 TURRET ASSEMBLY 630 1 14300 5 5 1 Compartment 1 Contact Board 630 1 14293 C1 Capacitor 27 pF 5 Type 310 N P O L1 Choke 0 22 uH 5 2 2 Filter Assembly 630 1 14289 400 4 98322 049 406 8 08324 009 Part No Filter 2 MHz 630 1 14057 Filter 2 3 MHz 630 1 14058 Filter 3 4 MHz 630 1 14059 Filter 4 6 MHz 630 1 14060 Filter 6 9 MHz 630 1 14061 Filter 9 14 MHz 630 1 14062 Filter 14 21 MHz 630 1 14063 Filter 21 30 MHz 630 1 14064 55549 Compartment_2 Contact Board 630 1 14292 Resistors Part No Nos Value Tol Rating Maker and Type ohms Watts 1 10 Erze 16 403 4 78168 0 19 2 403 4 18168 105 3 403 4 18168 117 4 403 4 78168 181 5 Erie 16 403 4 18168 089 6 i Erie 16 403 4 78168 161 T 2
23. GENERATOR MODULATOR L O IN TERP ost O SYHTH OUT TO BOARD H mo BOARD TURREY H FILTERS PHASE DETECTOR OUTPUT TO TO ISOLATING MODULE i TO 5 6 O FROM DC AMP BOARD O FROM PHASE DETECTOR ust CP LACK DIODE CONTROL EI BLACK DIODE CONTRO to 809 3 T aco reactor ASY O FROM 1 0 15Y0 TO TURRET TO ISOLATING AMP a TURRET INTERCONNECTIONS PHASE LOCK CIRCUITS SELECTION COMPARTMENT 2 COMPARTMENT WAFER Fe TO SPECTRUM GENERATOR AERIAL AR M00 310 HOD LO 15v RF FILTERS ISOLATING A 22 MODULE TO ISOLATING AMP b COMPONENTS BOARD POSITIONS FIG 3 R F TURRET FLI O 2 Mej tt us 2 3 FL 3 4 FL 4 6 FILTER LS 4 FL 14 FLO 21 30 TO WAFER WAFER 5 FILTER 2 6 TO WAFER YO AF IN FIXED SKT 02 TO WAFER D TO set 23 BOARD A2 BOARD Modifications Fig 4 issue 2 FIG 4 1 12 Ts Ta s Te fe To 611112 FIG 4 TURRET 1 FILTER CIRCUITS TURRET COMP 5 52 Vey EI 2 ce Gd 07 2 L6 icis 1 ss 072 VT3 5 A ms Rte e 35 3
24. Inan tor Assembly 11 turns 406 8 08324 005 L9 111 1113 2 139 144 143 1n i r Assembly 11 turns 406 8 08325 005 L14 L10 L44 L46 t Assembly 9 turns 406 8 08324 006 L15 L17 145 147 Inau lo Assembly 9 turns 106 8 08325 006 18 120 2 049 550 Indie sor Assembly 8 turns 406 8 08324 007 1 L23 8 149 151 153 Inductor Asconbly 8 turns 106 8 08325 007 1 PELO LIO 3 L54 L591 aye tor A comedy turn 406 8 08324 008 t qub poo LOS baro Intir or Assembly f burn Auo 0 05325 008 P3 155 ET Issue 5 5 6 Resistors 1 11 16 28 2 26 3 9 14 21 27 33 4 5 6 10 15 18 24 25 30 T 12 8 13 20 32 19 22 31 39 23 N 6 8 17 28112 10 11 12 16 18 19 20 13 14 15 Miscellaneous Issue Y 17 34 Compartment 3 Board 630 1 14105 Rating p id Value Tol ohms 82 10 Erie 16 403 4 18168 053 t Erie 16 403 4 18168 141 t Erie 16 403 4 18168 153 16 403 4 18168 089 i 16 4C3 4 18168 109 i Erie 16 403 4 18168 125 i Erie 16 403 4 18168 039 i Erie 16 403 4 78168 077 i Erie 16 405 4 18168 023 i 16 403 4 78168 137 4 16 403 4 18168 093 16 403 4 78168 057 Mullard C280 Erie N750 AD Erie N750 BD Mullard C280 400 4 98268 001 400 4 98308 112 400 4 98439 019 400 4 98268 005 400 4 98260 016 401 4 98023 004 400
25. c unearthed is applied to the regulator circuit via the bridge rectifier this method of connection protects all circuits against damage due to reverse polarity since the rectifiers ensure that correct polarity is always observed 1 5 CONTROLS AND INDICATORS 11 functional controls and the monitoring meter are mounted on the receiver front panel Selector links are located on the rear panel The controls and their functions are detailed below Control switch 51 four position switch used to switch the receiver into one of the conditions OFF STANDBY ON or CALIBRATE Mode selector switch 82 The required mode of operation is selected by the setting of 52 Five modes are provided USB LSB CW AM and FSK One extra switch position is provided to accommodate other modes if required MEGAHERTZ control This control is used to set the turret to operate at the megahertz appropriate to the frequency of the receiver signal Indication of the selected frequency is given on amp MECAHERTZ film scale Tuning control kHz Used to tune the interpolating oscillator and drive the KILOHERTZ film scale to indicate the tuning Setting Fast or slow motion drive is available dependent upon the setting of the SLOW FAST SLOW control below the tuning control Issue 1 10 PR155C BANDWIDTH switch 53 switch 84 BFO control AUDIO GAIN control RV2 RF IF GAIN control RV1 Loudspeaker ON OFF switch Meter
26. gt 9 9 9 Diode Zener 6 87 Transistor BSY95A Selected Inductor Assy 7 turns Inductor Assy Choke RF Miniature 100uH Inductor Assy Ceramic NPO AD Ceramic NPO AD Polystyrene Ceramic N560 AD Ceramic N750 A Ceramic NPO AD Miniature Foil Miniature Foil Ceramic 831T Polystyrene Polystyrene 11 turns Erie 1 Erie Erie Erie Erie Erie Erie Erie Frie Erie Erie Erie Erie Erie Fixed Composition Erie 15 58 400 4 98514 105 400 4 98047 006 400 4 98179 016 400 4 98394 033 400 4 98308 106 400 4 98047 007 400 4 98268 007 400 4 98268 005 400 4 981 90 052 400 4 98179 015 400 4 9821 2 023 Potentiometer Mini Flat Pot Painton 25K 404 4 98118 001 Potentiometer Type G MK2A 5000hms Diode IN4148 Diode Zener 107 Diode Zener 2 415 4 98393 415 4 98148 417 4 98530 406 1 08459 403 4 78257 157 403 4 78257 172 403 4 78257 181 403 4 78257 161 403 4 78257 154 403 4 78257 174 403 4 78257 178 405 4 18257 176 403 4 18257 162 405 4 18251 158 405 4 18251 160 403 4 78257 163 405 4 18251 182 405 4 18251 165 403 4 78229 161 404 1 00405 002 415 4 98167 003 415 4 98161 005 415 4 98167 009 406 4 08324 008 406 4 08324 005 406 4 9801 2 003 403 4 18257 150 PR155C Capacitors Value 400 4 96266 007 Part No Miniature Foil 402
27. mixer employs transistors VT3 and in a conventional balanced mixer configuration The first IF signal at 57 5 MHz is applied to 5 base and emitter and the 48 MHz signal from VT7 is applied to VI3 emitter VPA base Consequently the signals are mixed and appear across the common collector load R25 The required second IF of 10 7 MHz is selected in the crystal bandpass filter and coupled via C25 R28 to the second IF amplifier in module 5 3 10 SECOND IF AMPLIFIER AND THIRD MIXER MODULE 5 Fig 15 The first stage VT1 of the second IF amplifier in module 5 is similar to the first stage of the third IF amplifier in Module 7 3 12 VT is connected across the reference and AGC lines the emitter load of the stage is very much greater than the collector load the stage gain would approach unity however D2 controls this gain During the reception of weak signals it is forward biased but its impedance increases as the signal strength increases The output from VT1 is amplified by VT3 and this stage feeds the third mixer and VT5 The 100 kHz second IF signal is applied to base and VT5 emitter and the signal from the 10 6 10 8 MHz generator module 11 is applied to VT5 base and VT4 emitter The resultant 100 kHz output is coupled via C15 emitter follower VT6 and the bandwidth filter selected by the setting of 55 to the 100 kHz amplifier in module T 3 11 10 6 10 8 MHz GENERATOR MODULE 11 MKTI Fig
28. output using the internal speaker as monitor Set RV1 on module 9B accessible through handle to the fully clockwise position and measure the audio output voltage using a valve voltmeter This should not be less than 24457 10mW in 600 ohms b AM Increase the signal level to e m f and modulate with a 1 kHz tone at 30 Switch to and select 6 kHz filter Measure the AF cutput which should not be less than 2 457 SSB Remove the modulation and return the signal level to 0 5uVa Select the USB mode and tune the receiver to give approximately 1 kHz tone from line Measure the output which should be not less than 2 45V r m s 4 47 AGC TESTS 4 7 1 Threshold Levels Set the AGC switch to 0 1 sec and the mode switch to USB Switch to SSB bandwidth and adjust the RF IF gain control to maximum Inject a signal of O 5uV e m f at 15 MHz into the 75 ohm AERIAL socket and adjust RV1 on module 8 for 65 mV e m f at the 100 kHz output unloaded Note the audio output level across the 600 ohm line b Raise the input signal level in 10dB steps by 120dB The audio output level should not vary by more than 4 dB above the reading obtained in a 4 7 2 Decay Times To check the decay times proceed as follows a With the conditions as in 4 7 1 a above set the AGO switch to 7 0 secs and connect an between the A G C line and earth Set the signal generator to 80dB above O 5uV Switch out 40
29. satisfactorily at all positions previously tested If satisfactory results are obtained remove the test equipment and reconnect the coaxial cables 4 13 ISOLATING AMPLIFIERS With a signal at frequency of 50 MHz and an e m f of 1V applied at the input cable 8 the isolating amplifier the voltage measured on a valve voltmeter connected across 75 ohm load at the output connector cable 9 should be not less than O 5V r Mm Se 4 14 METER CIRCUITS 4 14 1 S O Adjustment Set the MODE selector to USB the BANDWIDTH to 3kHz and the gain control to maximume Switch the AGC to 0 1 secs and apply a signal of 15 MHz at 1 to the 75 ohm AERIAL socket Adjust RV3 on the meter circuit board to give reading of 5 0 on the front panel meter with 56 switched to RF 4 14 2 S 19 Adjustment With conditions as in 4 14 1 increase the signal level to 100uV and adjust RV2 to indicate 59 on the front panel meter Reduce signal level to 10 and recheck 5 0 setting If further adjustment is required repeat 4 14 1 and 4 14 2 until both conditions are satisfied Lock RV2 and RV3 34 PR155 Issue 5 5 COMPONENT FORMATION When ordering spares it is advisable to quote the serial number of the receiver module number and part number as quoted in this handbook operational spares kit is available fuses indicator lamp under part number 630 LF 14375 A maintenance spares kit resistors capacito
30. switch 56 AF RF Selector links Indicator lamp ILP1 PR155 S5 1 The appropriate bandwidth is selected by this switch SSB 150 Hz 300 Hz 1 4 kHz 3 5 kHz 6 0 kHz 12 kHz The receiver IF gain is controlled by the IF gain control when 54 is set to OFF and by when 54 is set to 0 1 1 sec 10 Used to tune the BFO by 8 kHz about its nominal frequency Used to adjust the gain of the audio amplifier AGC off Manual gain control on threshold control Used to switch the internal loudspeaker on or off Used in conjunction with the meter M1 to monitor the audio output as 15 meter for tuning link is provided on the rear panel for selection of either 150 ohm a 600 ohm line output Further links enable the internal oscillator to be disabled when external oscillators are to be used This lamp is lit when the control is turned from the OFF position Located in M1 aiie Issue 6 2 INSTALLATIC s 42 UP AND OPERATION Cas ihe BER 2 1 INSTALLATION 2 1 1 General When received the 155 should be inspected for sign of damage with particular attention to the front panel meter and the correct mechanical operation of switches and controls the top and bottom covers by first removing the four securing screws and pushing the co er forward from the back of the receiver and ensure that all coax
31. this volume Multimeter 85 CT497 6625 99 943 1524 b T75ohm Resistor 3 in 5905 99 013 5463 c Multimeter Electronic CT471 6625 99 972 0247 Signal Generator 4524 6625 99 580 6581 and Signal Generator CT433A 6625 99 1 95 4684 e Multimeter Electronic CT471 6625 99 972 0247 600ohm Resistor Use 2 in No 5905 99 022 1166 300ohm 5600hm Resistor 5905 99 01 3 5484 h Counter Electrical Frequency CT488 6625 99 971 8519 j Signal Generator CT432A 6625 99 195 4684 Oscilloscope CT436 6625 99 914 2605 no storage facility 4 3 POWER SUPPLY The D C supply to the receiver circuits should be 15V to 16V with the control switch set at STANDBY and at ON This can be measured at pin 4 or pin 6 of most of the modules 4 4 OVERALL RECEIVER GAIN The overall gain of the receiver may be tested in the following manner a Set to OFF BANDWIDTH to 3 kHz SSB and the mode selector switch to USB Switch on the receiver and adjust the RF IF GAIN control to maximum PR155C 25 Issue 1 b Connect a valve voltmeter the 100 kHz OUTPUT socket and connect the output of a signal generator to the 75 ohm AERIAL socket c Adjust the signal generator for an output of 0 5uV at 15 MHz and tune the receiver for maximum indication on the valve voltmeter An indi cation of approximately 80mV r m s should be obtained d Repeat c at 30 MHz and 1 MHz respectively An indic
32. 04 1 00405 005 PR155 5 13 2 Unit 9B 630 1 14084 Resistors i 403 4 78168 109 1 Tees 403 4 78168 105 5 405 4 18168 155 403 4 78168 089 403 4 78168 053 3 405 4 18168 161 2 405 4 18168 1 25 4 403 4 78168 177 405 4 18168 115 403 4 78168 017 403 4 78168 1 37 Capacitors Plessey Electrolytic 402 1 01223 001 Electrolytic 402 8 50833 029 Lemco Ceramic Hi k 400 4 98113 006 Lemco Ceramic Hi k 400 4 98113 010 Plessey Electrolytic 402 1 01200 015 Miscellaneous RV1 Potentiometer 5k ohms 404 1 00405 024 RV2 Potentiometer 100k ohms 404 1 00405 006 VT1 to Transistor 25512 BSY95A 9 417 4 981 38 PR155C 55 amp 54 Issue 1 5 14 ll GENERATOR 020 1 14220 5 14 1 Board tA 630 1 14931 Resistors Value Tol Rating 8 10 Fixed Composition 403 4 78168 121 9 12 Fixed Composition 403 4 78168 149 10 Fixed Composition 403 4 78168 113 11 19 Fixed Composition 403 4 78168 105 Fixed Composition Fixed Composition Fixed Composition Fixed Composition Fixed Composition 403 4 78168 097 Fixed Composition 403 4 78168 073 Fixed Composition 403 4 78168 129 Fixed Composition 403 4 78168 069 Fixed Composition 403 4 78168 093 Fixed Composition 402 4 18168 211 Fixed Composition 403 4 78168 195 Fixed Composition 402 4 18168 065 Erie Type 15 Erie Type 15 Erie Type 15 405
33. 08 002 Transistor ACY19 Mullard 417 4 98170 Transistor 00200 Mullard 417 4 98190 Reg Board Assy oda 5 19 Meter Amplifier 630 1 17742 Resistors Value Tol Rating Selection on test Erie 16 402 4 18168 151 Erie 16 403 4 18168 191 Erie 16 403 4 78168 109 PR155C 60 Issue 1 Capacitors 403 4 18168 065 403 4 18168 149 403 4 78168 057 403 4 78257 167 Lemco SM 402 4 98009 039 a 0 T Mullard C280 400 4 98268 007 BB Miscellaneous 5 20 Resistors RV Potentiometer 100k 404 1 00405 006 RV2 Potentiometer 1k E D1 D2 D4 D5 Diode 14148 415 4 98295 D3 Diode Zener 127 ZF12 415 4 98167 011 1 Transistor BOYTO 417 4 98267 001 RV3 Potentiometer 2500hm 404 1 00405 008 A G C Decay Shaper 630 1 17869 Value Tol Rating 405 4 18251 041 403 4 78257 170 403 4 78257 174 403 4 78257 190 403 4 78257 243 403 4 78257 203 405 4 18251 112 Miscellaneous Issue 1 RV1 Potentiometer Lin 1k 20 404 1 00405 010 D1 Zener Diode 4 7V 5 415 4 98167 001 D2 Diode IN4148 415 4 98595 1 Transistor 411 4 98261 001 61 PR155C Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Tig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig PR155B nu xM N gt 6 DRAWINGS AND ILLUSTRATIONS PR155 Chassis Layout PR155 Schematic Dia
34. 100 Issue 1 56 PR155C Miscel 2 15 Resist EUH laneous Circuit Ref Inductor Description Miniature Choke 1000uH Miniature Choke 100 uH Ferroxcube beads 6 off Diode IN4148 Diode Zener 10V 5 Transistor 25512 Texas Insts BSY95A 5195 406 6 9801 2 005 406 4 9801 2 003 905 4 98052 415 4 98393 415 4 981 67 003 417 4 981 38 MODULE 11 MKII 10 6 10 8 MHz GENERATOR 630 1 1 8 ors ON AUP N 11 15 18 21 24 PR155C 12 14 17 20 25 13 16 19 22 25 26 27 10 Rating Watts de eaten iei Pp ele 57 406 4 08324 005 Composition Composition Composition Composition Composition Composition Composition Composition Composition Composition Composition Composition Composition Composition Composition Composition Composition Composition Composition 402 4 18168 105 405 4 18168 049 403 4 78168 117 403 4 78168 181 403 4 78168 089 405 4 18168 219 405 4 18168 161 405 4 18168 115 405 4 18168 015 403 4 78159 034 403 4 78159 032 403 4 78159 030 403 4 78168 057 403 4 781 68 145 403 4 78168 165 403 4 78168 097 403 4 78168 053 405 4 18257 178 405 4 18168 109 Issue 1 Capacitors Module 12 630 1 26390 001 Resistors 6 7 15 18 8 10 11 12 19 13 14 16 20 22 25 24 Issue 1
35. 4 18251 110 403 4 78168 039 403 4 78168 161 Se Erie Type 15 403 4 78168 154 Value Tol 20 5 7 8 10 Miniature Foil 400 4 98268 007 11 12 13 5 Miniature Foil 400 4 98 68 007 14 26 28 9 16 17 Polystyrene 400 4 98119 011 20 20 Ceramic 400 4 98038 114 21 Ceramic 400 4 98038 106 23 Erie NPO AD 1400 4 98425 118 24 25 Polystyrene 400 4 98179 010 Plastic Dielectric 401 4 98085 Trimmer Polystyrene Fixed 400 4 98425 001 400 4 98425 087 PR155C 55 Issue 1 Miscellaneous Circuit Ref RF Choke miniature 22uH RF Choke miniature 4 TuH Transistor Transistor 407 Diode IN148 Crystal 1 MHz 406 4 9801 2 006 406 4 9801 2 001 417 4 03007 016 417 4 98138 417 4 981 55 415 4 98393 428 4 98034 5 14 2 Board B 630 1 14271 Resistors Value Tol Rating nae Yao y tino ant art moe 10 i 16 402 4 18168 051 10 16 403 4 78168 105 10 i 16 403 4 78168 117 10 i 403 4 78168 181 10 2 405 4 18168 089 10 2 403 4 78168 161 10 405 4 18168 115 10 405 4 18168 065 10 2 403 4 78168 039 10 2 403 4 78257 161 2 405 4 18251 011 Capacitors Ceramic 400 4 98322 049 Ceramic 400 4 98425 085 Polystyrene 400 4 98179 016 Ceramic 400 4 98425 089 Ceramic 400 4 98425 087 Mullard C280 400 4 98268 001 Mullard C280 400 4 98268 007 Ceramic 402 4 98260 016 Lemco SM 400 4 98009 039 Ceramic 400 4 98308
36. 4 98009 039 400 4 98719 001 400 4 98268 001 400 4 98179 011 Miniature aluminium Polystyrene Polystyrene Polystyrene Miscellaneous 11 12 13 Choke 100uH 406 4 98012 003 D1 Diode Zener 4 7V 415 4 98167 001 02 04 Diode IN4148 415 4 98393 1 Transistor BSY95A 28512 8T95A 417 4 98138 Integrated Circuit SN7470N 445 4 98010 016 5 17 Isolating Amplifier 630 1 14541 Resistors Value Tol Rating ana pe DE 10 Erie 16 405 4 18168 081 10 ie 16 403 4 78168 137 10 10 16 403 4 78168 153 16 403 4 78168 089 16 403 4 78168 141 16 403 4 78168 073 10 10 ST am a La a Laa a Laa Miscellaneous C1 C4 65 Capacitor 001uF 20 40 Ceramic Hi k 400 4 98260 016 VT2 Transistor 28512 Texas Insts 417 4 98138 F1 F2 F3 UHF Min feed thro Ceramicon Brie CPT3000 400 4 98266 Board Component 630 1 14540 PR155C 59 Issue 1 5 18 Regulator 650 1 14608 Resistors Value Rating 1 Erie 1 403 4 78168 137 2 Erie 403 4 78168 153 Erie 16 403 4 78168 109 4 Erie 16 403 4 78168 117 i Erie 16 403 4 78168 101 Welwyn 3101 403 4 78220 025 Capacitors Plessey Electrolytic 402 1 01201 001 Tantalum 402 8 50854 017 Hunts 97 400 4 98507 010 Miscellaneous Potentiometer 1k ohms 404 1 00405 005 Diode Zener BZY88 C5V6 415 4 98328 Bridge diode 415 4 98164 Transistor 0025 Mullard 417 4 981
37. 4 98308 104 RN Ceramic H k Var able Er e N750 AD Er e N750 AD 404 1 00405 001 406 4 98012 002 905 4 98052 406 8 08329 003 417 4 98138 411 4 98135 Potentiometer 100 ohms RF Choke miniature 6 80H 10 Ferrite Beads 3 off Transformer Transistor 25512 SYJ5A Transistor 407 2N3983 Diode HG1012 Hughes International 6 195A 40 PR155 5 5 7 Compartment 3 Board 630 1 14107 Resistors t 1 2 19 26 10 Erie 16 403 4 18168 141 10 1 Erie 16 403 4 78168 093 Erie 16 403 4 78168 077 Erie 16 403 4 78168 023 Erie 16 403 4 78168 105 i Erie 16 403 4 78168 073 i Erie 16 403 4 18168 057 i Erie 16 103 4 78168 039 Erie 16 403 4 78168 153 i Erie 16 403 4 18168 113 Erze 16 403 4 18168 089 Capacitors 1 4 6 8 21 9 10 12 13 Lemco 400 4 98260 007 14 16 17 20 Ceramic H1 k Lemco 400 4 981 13 010 Ceram c H k N750 AD 400 4 98 308 106 Erie N750 AD 400 4 98308 114 Erie NPO AD 400 4 98308 096 Lemco 400 4 98179 012 Polystyrene Kemet K11N6 N5 402 4 98096 012 Miscellaneous L1 Inductor 5 turns 406 8 08324 009 L2 L Ferroxcube beads 6 off 905 4 98052 TR2 Transformer 406 8 08328 D1 D2 D3 D4 D7 D8 Diode HG 1012 Hughes International 415 4 98149 D5 D6 D ode IN4148 415 4 98 42 4 VT1 VT5 VTO Transistor Texas nsts 41
38. 400 4 98263 022 3 L C R Ltd Polystyrene 400 4 98263 010 4 L C R Ltd Polystyrene 400 4 98263 024 5 L C R Ltd Polystyrene 400 4 98263 016 6 L C R Ltd Polystyrene 400 4 98263 023 1 L C R Ltd Polystyrene 400 4 98263 025 Miscellaneous L1 Inductor 9T 406 8 08324 006 Inductor 8T 406 8 08324 007 Transformer 406 8 08329 002 Filter 37 3MHz bracket assy Diode HP2900 415 4 98403 630 1 14367 Board Component Unit 2 Transistor 11584 Issue 9 44 PR155 5 8 Module 3 1 Local Oscillator 630 1 14112 Resistors Value Tol Rating Erie 403 4 78168 195 403 4 18168 101 403 4 78168 117 403 4 18168 113 403 4 18168 0T1 403 4 18168 141 403 4 78168 093 403 4 78168 081 403 4 18168 057 403 4 78168 039 403 4 18168 045 ie pie Ine PP Pe e ene Capacitors Lemco Ceramic Hi k 400 4 98260 007 Ceramic 400 4 98308 112 Trimmer tubular 401 4 98023 003 ceramic Miscellaneous 21 Saturable reactor 407 1 21963 001 VT Transistor 2N3983 417 4 98135 VT3 VT4 Transistor 25512 BSY95A 57954 417 4 98138 Diode BA110 STC 415 4 98148 Diode IN4148 415 4 98393 F2 F3 FA UHF min feed thro Ceramicon Erie CFT 3000 400 4 98266 Board Component 630 1 14443 155 45 Issue 7 5 9 MODULE 4 630 1 14117 5 9 1 Unit 4A 630 1 14093 Value Tol Rating Maker and e Part No ohms Watts 403 4 18168 069 403 4 781
39. 5 R2 04 10 01 04 RF M i P 33 33 2 84 FRB 820 126 126 FIG 5 RF 954 56 AMPLIFIER MODULE Si 2 1009 3 RIT 390 82 9 39 Sra 857 954 m 954 19 04 644 RAS d 22 R45 5 330 450 9 39 04 o4 or E 126 46 24 625 04 OH 2 0985 R44 5 K 820 lyre psy M6 e CIRCUIT AND BOARD LAYOUT R24 270 ul 16148 1 0 820 104148 y vT6 BSY 25 40 ave R26 500 220 en 27 390 m E s lt u am 630 DA 17570 vAL IN PL 4 Ti 2 2 RF IN PL c O P 10 SHS ao AE AO O 94 1199 103p 639 2 CA 1 O FLI N 37 3 SKT RF OUT TR No 630 41 DWG No 630 FIG 6 FIRST MIXER MODULE 2 CIRCUIT AND BOARD LAYOUT FIG 6 MOD 2 z T FROM LO OUTPUT TUARET CONTROL 2 1 2 TSKT O 09 L Oureur TURRET bad 47 gt PL vT2 a 11407 p 1000p 03 TURRET CONTROL N4148 rus 3 1 DWG No 630 Da 14112 630 1 144 3 21195157189 par 2 FIG 7 PRI55 FIRST LOCAL OSCILLATOR MODULE 3 CIRCUIT AND B
40. 6 7Mc s AMP FILTER ro id TURRET Moston 2nd EOI HE MNA AMP GC er 4960 55 ZI MEE MEA be MODULE 5 10 py 90 jk 1 IMMO ad al 44 19 aTa lo 7 MODULE P s IE ues 6 n 15 1 i 4 4 1 8866 056 p Y E 45 J l ISOLATING H 1 W VV i RIO 396 AO 1 9 5 1 CONTROL 0 o 5 runner 100 Kejs af 2 1 coup 2 ISOLATIN x a 5 1 MODULE l a Q0 METER AMPLIFIER ya ech H pm 5 BE 25 o T 44 1 ES 3 4 5 85 1 to BRE 8 4 SPECTRUM yG zl SHAPER 56 EBA centraron v 1 LE 1 5 8 NA 9 4 9 820 IK RIS o 4 H1 o 1F GAIN VIVE A EDU c 8 0 00 ON OFF x o d offs L m J 4 ds IN SKT4 STAND s at AM NU o p orro 8802 5 A OFF lt 9580 o4 gt ya lt st 82 3 54 AGC SWITCHES SHOWN IN FULLY CCKWISE POSITION FIG 2 PRISS SCHEMATIC BLOCK DIAGRAM FIG 2 SCHEMATIC 155 INTERP OSC BOARD SPECTRUM MHz IN PHASE SPLITTER
41. 68 057 403 4 18251 052 403 4 18168 185 403 4 18168 153 403 4 78168 089 Resistors 1 2 3 5 6 14 19 24 8 13 15 18 20 21 22 1T 23 25 26 403 4 18168 169 403 4 18168 105 403 4 18168 137 403 4 18168 085 403 4 18168 129 403 4 18168 013 403 4 78168 023 PAP ERP ARP AIR gt eje 28 403 4 78168 053 Capacitors Miscellaneous Circuit Ref F2 4 rm VT2 VTA D1 Issue 7 Mullard C280 Film Polystyrene Polystyrene Polystyrene Polystyrene Polystyrene Ceramic Ceramic NPO DD Potentiometer 1k ohms Miniature RF Choke 6 8uH 10 Inductor 7T Inductor 4T UHF min feed thro Ceramicon Eire CTF 3000 Transistor GM378 Texas In s Transistor TI407 2N3983 Transistor 25512 Diode 1N4148 UGTU5A 31254 5 46 400 4 98268 001 400 4 98263 005 400 4 98263 027 400 4 98263 028 400 4 98263 029 24 98308 A 400 4 404 1 00405 005 406 4 98012 002 406 8 08324 008 406 8 08324 010 400 4 98266 417 4 98131 411 1 98135 11104 98138 4 98393 PR155 5 9 2 UNIT 4B 630 1 14095 Resistors Value Tol Rating 29 1k 10 403 4 18168 105 403 4 18168 065 403 4 78168 153 403 4 78168 089 403 4 78168 113 403 4 18168 039 403 4 78168 071 403 4 78257 161 o Ceramic 100 4 98038 104 Erie N750 AD 400 4 98308 100 Ceramic 400 4 98425 044 Ceramic 400 4 98425 087
42. 78168 177 403 4 78168 129 403 4 18168 113 403 4 18168 145 403 4 78257 161 Value 17 1 4 1 4 1 4 1 4 1 4 i 4 i amp i 4 i 4 i 4 i 4 i 4 1 4 Mullard 02954 400 4 98245 004 Mullard C426 402 4 98031 034 Mullard 426 402 1 9803 1 035 Mullard 0280 400 4 98268 007 Mullard 02954 400 4 98245 003 Erie 811 K350081 400 4 98113 010 Mullard C426 402 4 98031 032 Electrolytic 402 8 50833 029 Miscellaneous VT6 VT11 Transistor BSY95A 28512 8T95A 417 4 98138 D4 Diode 1N4148 415 4 98 393 L5 L6 RF Choke Miniature 1000uH 406 4 98012 005 Transformer 14MM 406 8 08326 002 T2 Transformer 26MM 406 8 08220 009 Issue 6 50 155 5 12 Module 8 630 1 17750 Resistors Maker and Type 16 Frie 403 4 18168 121 Erie 16 403 4 78168 125 Erie 16 403 4 18168 153 16 403 4 18168 093 Erie 16 403 4 18168 133 Erie 16 403 4 78168 137 Erie 16 403 4 78 168 173 Erie 16 403 4 78168 145 Erie 16 403 4 78168 199 Erie 16 403 4 78168 065 Erie 16 403 4 78168 089 Erie 403 4 18168 161 Mullard C280 400 4 98268 007 Mullard C295A 400 4 98245 009 S T C Tant 402 4 98022 027 Electrolytic Electrolytic 402 8 50833 029 Plessey Electrolytic 439 1 02106 451 Wima Tropyfol M 640 8 08705 003 Plessey Electrolytic 02 1 013 001 Mallard C426 AR F 402 94312 901 Miscellaneous
43. 88 manually and note the time it takes the A G C voltage to decay this should be approximately 1 second b Repeat the procedure with the A G C set to 10 seconds The decay time should be approximately 10 seconds c If these results cannot be obtained adjust RV1 on the A G C Shaper Board until satisfactory results are obtained 4 8 SIGNAL NOISE PERFORMANCE Measure the signal noise performance of the receiver as follows Set 0 to OFF BANDWIDTH to 6 kHz and select the AM mode Turn both gain controls fully clockwise Issue 5 28 PR155 4 9 4 9 Inject 150 kHz unmodulated sigral at a level of 8uV at the 75 ohm aerial socket Tune the receiver at 150 kHz for maximum noise output Adjust the AUDIO GAIN control for a convenient output level on the milli voltmeter connected across the 600 ohm line output and note this level Apply modulation at 1000 Hz to a depth of 30 to the input signal The audio output should increase by at least 1088 c Set BANDWIDTH to SSB and select the USB mode Increase the input signal frequency to 15 MHz and set the level to 210 Tune the receiver to obtain an audio output of approximately 1 kHz Set IF GAIN to maximum and adjust AUDIO GAIN for a convenient reading on the millivoltmeter Note the reading then remove the input signal the meter reading should fall by not less than 2098 e Select the LSB mode Without resetting any other receiver controls inject
44. ARD See Fig For Overall Mod State 15V A4 RIB ren Ral 100 47 47k 478 c4 25 3 A o T oi MODULE 2 47K 4 E MIXER 5 zac c n RN Cep m es 01 BOARD 4 Ca GM378 E LI E 535 68 pH oj 8 pN 33 T 58 Di Dirt e C23 25 100 ol 7p 825 a acr 10 7 SKT ma Melt 13 Ano RI C6 Ra Al R23 R25 636 80 75 410 80 390 276 18 Ot 9 PL 12 TO BOARD 4 4 Im 4 a sv J 4 26 T 5 em 2p C28 16 85 95A 29 4 78 O L6 o 05012095 FIG 14 FIG I4 55 FIRSTI F AMPLIFIER AND 2nd MIXER MODULE 4 CIRCUIT AND BOARD LAYOUT 100 4 4 Quiv 19 6 i n22 R25 827 47 47K 560 ciue A28 o 55 100xHz 15K rs 857 95 14 cz 6 74 8 IN wu NM gt PL a m L 022 IN4148 022 C7 R26 2 O REFERENCE 4 10 6 10 6 Hz osc IN 15 Li 3 000 OAGC Treo t FIG 15 PRI55 2nd I AMPLIFIER AND 3rd MIXER MODULE 5 CIRCUIT AND BOARD LAYOUT SKY 31 AS 470 c2 3 9 264 3 54 a rt vr ZE CAS ORA
45. FIERS Fig 22 The isolating amplifiers provide buffer stages between the first local oscillator and the phase lock loop circuits and prevent spurious oscillation They consist of an amplifier stage 1 and an emitter follower VT2 The local oscillator signal is injected VT1 emitter in the first isolating amplifier the signal from the second isolating amplifier VT emitter is coupled to the phase lock circuits via C5 R8 5 18 MAIN CHASSIS Fig 1 5 18 1 Power Supply On mains operation the primary power supply is routed to the mains transformer T2 via FS1 and the double pole toggle switch section of the control switch 51 The primary of T2 is in two sections each with tappings to permit operation on any of the prescribed mains voltages The 22V output from T secondary is applied via FS2 to the bridge rectifier The DC output is smoothed by C2 and applied to the receiver circuits via a voltage regulator conventional regulator circuit is used employing with a reference voltage obtained from zener diode D1 5 6V Transistor is followed by two emitter followers VI4 and VT2 which drive the series regulator transistor On d c operation floating d c supply is connected at terminals 5 and 6 on the terminal strip on the receiver rear panel and is thus connected into the regulator circuit via 12 primary F2 and This method of connection provides protection by F2 and avoids the possibili
46. OARD LAYOUT 1 76 12 cau seo 69 20 55 82 PL SPECTRUM 30 TO MODULE 29 es pagado leas 22k FT PR SUN Of me iE 320 NS gt 7 gt E P que c Md a r cl BSY0SA Ch Sorat 1000p LE nn u ee DWG No 5308 1493 COMPONENT LAYOUT BOARD A nae BOARD 1 MES DSCILLATON B 6080 amp rx 8 3 Pi a A ts 1 7 3 i 9 99 L ssy 4 C ceca sw RER f 01 Sar so 37 t L 1 AND MIXER 1 mone 4 1 e 1 T t 1 1 4 T l 4 1 1 1 48 mcis SELECTOR T 570 55 1 FILTER BOX 1 ki E A 4 DWG Me 6233 14930 DWG No 630 1427 COMPONENT LAYOUT BOARD FIG 6 SPECTRUM GENERATOR 48MHz SELECTOR MODULE IO FIG 8 MODULE IO Cle c9 lov La 180 1900254 3 000 O als 560 Wie Cu 56 C3 4 RIT cie 56 sol RIB i w x 4 336 y T sir BSY95A 85795 Bv eT KILOCYCLES TUNING c s t Ot 630 DAJ14000
47. ODULE 7 21 3 13 AMPLIFIER AND DETECTOR MODULE 8 21 3 14 AUDIO AMPLIFIERS MODULE 9 22 3 15 100 kHz DIVIDER AND CALIBRATE CIRCUIT MODULE 12 23 3 16 BFO 23 5 17 ISOLATING AMPLIFIER 25 5 18 MAIN CHASSIS 25 4 SERVICING 25 4 1 GENERAL 25 4 2 TEST EQUIPMENT 25 4 3 POWER SUPPLY 25 4 4 OVERALL RECEIVER GAIN 26 4 5 STAGE GAIN 26 4 6 PRODUCT DETECTOR AND LINE AMPLIFIER GAIN 27 4 7 AGC TESTS 28 4 8 SIGNAL NOISE PERFORMANCE 28 4 9 AUDIO PERFORMANCE 29 4 10 CALIBRATION 30 Issue 1 2 PR155C PR155C OSCILLATORS PHASE LOCK CIRCUITS ISOLATING AMPLIFIER METERING CIROUITS 5 COMPONENT INFORMATION 6 DRAWINGS AND ILLUSTRATIONS 50 52 54 55 65 Issue 1 Frequency Range Modes of Reception Frequency Stability Drift with change of ambient Bandwidths Sensitivity up to 30 1 MHz Tuning Tuning Accuracy Scale Reading Accuracy Calibration A G C Time Constant IF Output Audio Output Issue 1 TECHNICAL SUMMARY 60 kHz to 20 1 MHz continuous coverage will operate down to 15 kHz with slight degradation of performance A1 MCW A2 DSB A2 USB LSB A3J A3H FSK F1 One spare switch position for additional mode After 4 hour warm up at steady ambient less than 30 Hz drift per hour Less than 40 Hz per after 5 hour warm up Filter 64 point 604 point Shape 150 Hz 150 Hz 1 8 kHz Symmetrical 500 Hz 500 Hz 5 0 kHz Symmetrica
48. Spurious Responses Spurious Response to external signals Blocking Cross Modulation Inband Intermod Outoof Band Intermod Power Requirements Environment Dimensions and Weight PR155C 150 ohm line 40 mW Loudspeaker 400 mW 600 ohm line 10mW Headphones mW Typically 8dB Within 4dB from 300 Hz to 12 kHz May be switched to 15 or audio level to line 7265 Not less than 80dB Less than equivalent 0 2 uV e m f all responses except 1 MHz and 21 4 MHz which is less than 2uV e m f equivalent between 400 kHz 30 1 MHz Better than 50dB for signals 10 to 35kHz of tune better than 8008 for signals above 35kHz of tuae With receiver tuned to any frequency between 2 MHz and 30 MHz and a wanted signal level of 1uV e m f the level of an interfering signal 10 kHz removed required to reduce the output by 388 is greater than 400uV e m f This level increases with the frequency separation With the receiver tuned to any frequency between 2 MHz and 50 MHz and amp wanted signal level of 1mV e m f the level of an interfering signal 10kHz removed required to produce cross modulation 2088 down on reference 1mV 30 modulated is greater than 80mV e m f This level increases with the frequency separation 2nd order 30dB 3rd order 35dB With the receiver tuned in for cross modulation two interfering signals 65dB reference level producing 1298 S N ratio and spaced 10kHz and 20kHz from N
49. THE PLESSEY COMPANY LIMITED PLESSEY RADIO SERVICE MANUAL FOR PRIS5B MF HF COMMUNICATIONS RECEIVER Publication No 0618 Issue 1 C 1973 Plessey Company Ltd The information contamed herein 15 the property of The Plessey Company Limited and 13 not to be disclosed or used without the prior written permission of The Plessey Company Limited This copyright extends to all the media in which this information may be preserved including magnetic storage punched card paper tape computer print out or visual display THE PLESSEY COMPANY LIMITED PLESSEY RADIO MARTIN ROAD WEST LEIGH HAVANT HAMPSHIRE TELEPHONE HAVANT 070 12 6801 THLEX 80227 CONTENTS Page TECHNICAL SUMMARY 4 General View of PR155 6 1 INTRODUCTION 1 1 1 GENERAL 7 1 2 MECHANICAL DESCRIPTION 7 1 3 MODULES 8 1 4 BRIEP TECHNICAL DESCRIPTION 9 1 5 CONTROLS AND INDICATORS 10 2 INSTALLATION SETTING UP AND OPERATION 12 2 1 INSTALLATION 12 2 2 SETTING UP 12 2 5 OPERATION 14 3 CIRCUIT DESCRIPTION 15 3 1 RF FILTER UNIT 15 3 2 RF AMPLIFIER MODULE 1 15 3 3 1ST MIXER MODULE 2 16 3 4 1ST LOCAL OSCILLATOR MODULE 3 16 3 5 SPECTRUM GENERATOR MODULE 10 17 3 6 INTERPOLATING OSCILLATOR 17 3 7 MHz SELECTOR TURRET COMPARTMENT 2 18 3 8 PHASE LOCK CIRCUIT TURRET COMPARTMENT 3 18 3 9 1ST IF AMPLIFIER AND 2ND MIXER MODULE 4 20 3 10 2ND IF AMPLIFIER AND 3RD MIXER MODULE 5 20 3 14 10 6 10 8 MHz GENERATOR MODULE 11 20 3 12 3RD IF AMPLIFIER AND DETECTORS M
50. ade to slide freely in their locating block in order that each may be individually unsoldered to facilitate module removal Of the other four the BFO interpolating oscillator and turret modules are mounted above the main chassis member the turret module protruding through from the underside on which the isolating amplifier is mounted Apart from coaxial connectors all interconnecting wiring is contained in cableform below the chassis and behind the front panel All operational controls are mounted on the front panel The MEGAHERTZ and tuning controls are coupled to the turret and interpolating oscillator respectively via Oldham couplers On the rear panel are located the mains fuse holders three link panels and the provisions for external connections to the receiver in the form of plug sockets and terminal block PR155C 7 Issue 1 1 3 MODULES ligt of the modules contained within the receiver 18 given below Eleven of these are of similar construction consisting of one or two printed circuit component boards and designed to fit into sereened compartments on the main chassis the screening being completed by an end plate which also serves ag handle for the removal of the module aid identification each of the modules is given number as indicated in the list ltem Module No Part No RF Amplifier 1 630 1 17670 1st Mixer 2 630 1 14111 1st Local Oscillator 3 630 1 14112 Amplifier 2nd Mixer A 630
51. ating oscillator which is tunable over the range 2 2 MHz to 5 4 MHz The spectrum generator output is fed into turret compartment 3m via compartment 2 in which the spectrum generator frequency appropriate to the frequency of the received signal 18 selected by means of tuned selective amplifiers tuning beins effected by sel e tion of coils as a result of the turret setting and only the required megahertz signal is applied to compartment 3 In compartment 3 the signal from the interpolating oscillator is added to the megahertz signal to produce a synthesized signal at the desired local oscillator frequency Provision is made for the use of external oscillators in place of either or both of the interpolating oscillator and the 1 MHz oscillator which drives the spectrum generator The output from the 185 local oscillator is also fed into compartment 3 via an isolating amplifier It is compared with the synthesized frequency to produce a control voltage which is used to tune the local oscillator exactly to the required frequency The 1st IF signal is filtered in module 2 by a crystal filter having a 12 kHz bandwidth It is then amplified and mixed with a 48 MHz 2nd local oscillator signal from module 10 for conversion to the 2nd IF of 10 7 MHz in the 37 3 MHz amplifier and 2nd mixer module 4 A second crystal filter follows the 2nd mixer and the filtered 10 7 MHz output obtained is amplifier and under goes the final stage of frequency conv
52. ation between 70 and 120mV r m s should be obtained e If satisfactory results are obtained proceed to 4 6 4 5 STAGE GAIN 4 5 1 Measurement and adjustment Should the overall receiver gain as measured in 4 4 not be satisfactory the stage gain may be verified and if necessary adjusted as detailed below Set the BANDWIDTH switch to 6 kHz a Module 7 Set the switch to 0 1 sec and the control switch to ON With no input signal into the receiver measure the voltage on the AGC line pin 3 on module 4 5 or 7 relative to chassis Switch the AGO OFF and adjust the RF IF GAIN over its full range The voltage measure on the AGC line should vary between at least 3 4 and 6 5V Turn the RF IF GAIN fully clockwise Set the Mode Selector switch to AM and break coaxial cable 16 input to module Inject signal at 100 kHz unmodulated at an e m f of 250uV into module 7 Connect a valve voltmeter across the IF output socket which should be unloaded and adjust RV1 on module accessible through the module handle so that the output is 78 to 84mV e m f Failure to obtain this output would indicate a fault in module 7 If a satisfactory result is obtained lock RV1 reconnect cable 16 and proceed b Module 5 module 11 and bandwidth filter Break cable 13 joining modules 4 and 5 and inject an unmodulated 10 7 MHz signal at an EMF of 25uV into the cable attached to module 5 Tune the input signal for maximum indication on the valve v
53. ator is swept quickly on to frequency and held for the duration of each sweep from the multivibrator PR155C 19 Issue 1 5 9 FIRST AMPLIFIER AND SECOND MIXER MODULE 4 Fig 14 The 37 3 MHz first IF output from the first mixer in module 2 is applied via C4 D1 and C5 to the base of the first of two IF amplifiers VM and 2 on board of the module Diode D1 has the AGC reference voltage 5 12 applied to its cathode and the voltage 3 13 applied to its anode it therefore introduces increasing impedance into the input circuits as the signal strength increases The AGC and reference lines are isolated from the first IF by and L2 The overall gain of the two IF amplifiers is controlled by the preset potentiometer RV1 which is adjusted on test for optimum output level The output from the second stage VT2 is coupled into the second mixer via a 37 3 MHz low pass filter Links are provided in the filter circuit to facilitate alignment The output of the 48 MHz selector circuit in module 10 is injected at the emitter of VT5 on board B This transistor in conjunction with VT6 operates in similar circuit to that of VT1 and VT2 of the 48 MHz selector circuit except that the output from VT5 is directly coupled to the next stage to provide a 48 MHz output which has extremely low spurious content The signal developed at VT6 emitter is coupled via emitter follower C30 and R34 to the second mixer on board The second
54. c Set RV1 on board B of module 9 fully clockwise and the line output links for 600 ohm line output Load the balanced line output with 600 ohms and measure the voltage across the resistor it should be not less than 2 45V r m s 10mW in 600 ohms Remove the 600 ohm load and set the links for 150 ohms line output Load the line output with 150 ohms and measure the voltage across the load it should be at least 2 45V r m s 40mW in 150 ohms PR155 29 Issue 5 4 9 2 Frequency response Audio frequency response should be checked follows a With the conditions as for 4 9 1 c adjust RV1 on module Y for an audio output of 0 77 remese on the millivoltmeter Amplitude modulate the input signal to a depth of 30 at 1 kHz Measure and note the audio output level to line c Change the modulation frequency to 200 Hz and then to 3 kHz noting the output level in each case this should be not less than 4dB down on the level at 1 kHz 4 9 3 Output adjustment With conditions as in 4 9 2 b set RV1 on module 9 to give 0 775 Se on the millivoltmeter Check that the front panel meter indicates to 1 16in when the meter switch is set to AF To test and adjust the meter circuits see 4 14 4 10 CALIBRATION 4 10 1 Interpolating oscillator Check that the KILOHERTZ film scale can be calibrated as detailed 1n 2 3 2 4 10 2 BFO Zero beat on any convenient 100 kHz point as detailed in 4 10 1 above
55. cuit when USB LSB are selected at 52 while the 100 kHz signal from module 12 5 15 is injected into the transistor emitter circuits for carrier reinsertion on 558 operation and the BFO 3 16 output is similarly injected on operation The detector output is coupled via R44 C44 to the base of amplifier 9 conventional detector circuit is also used for AM operation it is energised when AM is selected at 52 The output from 10 is amplified in detected by 14 and the resulting audio frequency signal filtered and applied to 9 base is energised under 11 operating conditions to provide the AF signal output to the emitter followers VI10 and 11 and hence to the audio amplifiers in the module 9 3 14 and to the AUDIO GAIN control RV2 on the main chassis 3 13 AMPLIFIER AND DETECTOR MODULE 8 Fig 18 Module 8 is an AGC amplifier and detector which in conjunction with the AGO decay shaper board provides the main control for the receiver The signal level at which AGC action starts to be effective is set by threshold control potentiometer RV1 This is then applied to VT1 which is an emitter follower stage the output of which is applied to amplifying stage VT2 Transformer T1 in the collector load of VT2 provides impedance matching and PR155C 21 Issue 1 offers some selectivity to the circuit Components VT3 D1 R8 and C5 form the detector and voltage doubler stage sinusoidal
56. d the filters being located between the turret wafers C and D which serve as selector switches The filter inputs are connected to wafer D and their outputs to wafer C From wafer C the signal is fed via the filter C2 L1 and SKT3 PL3 to the RF amplifier module 1 The filter C2 L1 functions as an image rejector 3 2 AMPLIFIER MODULE 1 Fig 5 The RF amplifier comprises one stage of amplification VT1 followed by three emitter follower stages VT2 4 It is preceded and followed by variable attenuators in the form of shunt diodes which are selected for high storage to prevent diode non linearity effects The front end diodes are controlled by a local a g c loop and VT10 The voltage which operates the control transistor is produced by 10 which operates as a detector with the signal from VT3 emitter applied to its base via C10 R16 C15 Under no signal very low signal conditions VT9 is held non conducting since its base via R36 and emitter is returned to the 15V line Thus D and D2 cannot conduct and offer no attenuation to the input signal the signal level increases to 20mV the detector action of VT10 drives VT9 base less negative with the result that VT9 conducts drawing PR155 15 Issue 5 current via D1 and D2 decreasing its impedance thus applying vome abtlenuation to the input signal With further increases in signal strength 4 more current via D1 and D2 increasing the atte
57. ect free BNC Amphenol 508 4 28456 Socket elect free Amphenol 508 4 28434 Socket elect free Mk 4 508 1 40001 320 Belling Lee Min Twin Socket Type AA 508 4 28002 Belling Lee Min Free Plug 508 4 28041 Belling Lee Min Free Socket de eae 508 4 28382 Belling Lee Min Fixed Socket 508 4 28075 001 5 2 INTERPOLATING OSCILLATOR 630 1 14000 001 Resistors Value ea Rating 403 4 78168 169 403 4 78168 181 403 4 78168 121 403 4 78168 105 403 4 78168 153 403 4 78168 161 403 4 78168 069 405 4 18168 141 405 4 18168 089 405 4 18168 095 403 4 78168 1 37 405 4 18168 045 d d IUS S EPIS EP Mullard C280 IS Mullard 295 400 4 98245 001 Mullard C295A 400 4 98245 008 Mica moulded 424 4 98070 004 Trimmer 401 8 20006 Brie N750 AD 400 4 98308 106 Polystyrene 400 4 98179 019 Polystyrene 400 4 98179 010 Polystyrene 400 4 98119 015 Issue 1 56 PRI55C Miscellaneous Circuit Ref Description 404 1 00405 009 406 1 08379 406 8 08327 406 4 98012 002 406 4 980 12 005 417 4 98138 415 4 98167 003 630 1 14404 Potentiometer 10k ohms Coil Assembly Trimmer Coil RF Choke miniature 6 8uH 10 RF Choke miniature 1000pH 7 Transistor 25512 Texas Insts Diode Zener 10V 5 Component Board Assembly 5 3 B F O ASSEMBLY 630 1 23304 Resistors 403 4 18168 149 403 4 18168 161 403 4 18168 157 403 4 18168 121 403 4
58. ersion to 100 kHz in module 5 The 3rd local oscillator is the 10 6 10 8 MHz oscillator module 11 the output from which which is dependent upon the mode of operation selected being 10 8 MHz for USB operation and 10 6 MHz for other modes PR155C 9 Issue 1 The 3rd IF signal is filtered by one of seven bandpass filters the bandwidth being selected by the BANDWIDTH selector switch The frequencies of the filters fitted in the receiver are 3 kHz SSB 150 Hz 300 Hz 1 4 kHz 5 5 kHz 6 0 kHz and 12 kHz Final IF amplification and detection takes place in module 7 A product detector is used for SSB and operation and an envelope detector for AM The 100 kHz signal for carrier reinsertion on SSB is obtained from module 12 and BFO is provided for operation output from the detectors is applied to the audio amplifiers in module 9 which provide the receiver outputs AGC is applied to all IF amplifiers and the RF amplifier and is obtained from the AGO detector module 8 For calibration purposes marker pips at 100 kHz intervals derived in module 12 from the 1 MHz output of module 10 may be injected into the 1st mixer All stages of the receiver operate on 15V d c supply On mains operation the a c supply is stepped down to 22V and then rectified by a bridge rectifier the resultant d c being applied to the receiver circuits via a regulator circuit which maintains a 15V supply For d c operation the 24V d
59. first stage is also controlled by AGC Since the emitter load of VT1 is considerably greater than the collector load the gain of the stage would approach unity however diode D2 is included in the circuit to control this gain It is connected between the reference and AGC lines such that it is forward biased during reception of weak signals but its impedance increases with increase in signal strength Thus during reception of weak signals VI1 emitter load impedance is reduced by the parallel path C4 D3 R10 and the gain of the stage is greater than when the diode impedance is increased by action Zener diode 05 connected between 15 and earth in series with R10 provides the reference voltage of 4 77 with respect to earth The output from 1 is amplified in three similar stages VT2 and VTA and applied to emitter follower VT5 This stage provides an output via C20 R46 to the AGC amplifier module 8 and also drives a second emitter follower 10 which provides outputs to the detectors and the 100 kHz OUTPUT socket on the receiver rear panel The gain of the amplifier is controlled by RV1 placed between VT2 and VT3 Two detectors are contained in this module product detector for 558 and operation and an envelope detector for AM operation The product detector employs transistors VT6 and together with transformers T1 and T2 in conventional detector circuit The 15V d c supply is connected to the cir
60. gram PR155 RF Turret Turret Comp 1 R F Filters Module 1 Amplifier Module 2 First Mixer Module 3 First local Osc Module 10 Spectrum Generator Mk 11 Interpolating Osc Turret Comp 2 MHz Selector Turret Board G Phase Splitters and Modulator Comp Board H Phase Detector 3 Board J DC Amp Reactor Sweep Gen Module 4 First IF Amplifier 2nd Mixer Module 5 2nd IF Amplifier 3rd Mixer Module 11 10 6 10 8 MHz Generator Mk IT Module 7 3rd IF Amplifier Detector Module 8 AGC Amplifier Detector Module 9 Audio Amplifier Module 12 100 kHz Divider Calibrator Beat Frequency Osc Isolating Amplifier Power Supply Regulator Meter Amplifier and AGC Decay Shaper Iss OSCILLATOR BIASING WAFER 4 C2 PHASE LOCK CIRCUITS MODULE 10 12 TURRET COMP 3 E MODULE 12 INTERPOLATING OSCILLATOR FILTERS ISOLATING AMPLIFIER b BOTTOM FIG 1 PRIS5 CHASSIS LAYOUT 1 CHASSIS 600 50 LINE O P 29 9 A y P y u AAA LINE j DE 952 mU CIA CT eee NEUTRAL AERIAL SKT 1 er Low 2 HJ 4 75 posed o 7 RF FILTER 3 191 5 4 E UNIT f ae Ist mw 15 1
61. he BFO control to obtain the tone required 2 3 2 Calibration To calibrate the KILOHERTZ film scale first select USB or LSB the mode selector switch and then set the control switch to CALIBRATE Calibration pips will be heard at every 100 kHz when the receiver is tuned over the range of the tuning control and the adjustable cursor can then be set to the appropriate scale marking at zero beat condition of the pips Interpolation can be made between the 100 kHz markings on the scale to obtain accurate indication of the frequency of received signals NOTE This calibration is valid for all modes but calibration pips are not obtainable on or To set the BFO the mode selector switch should be set to USB the control switoh to CAL and tune for zero beat Change the mode Selector switoh to the CW position and adjust the BFO to obtain zero beat The BFO tuning control should indicate 0 Issue 9 14 PR155 3 CIRCUIT DESCRIPTION 3 1 FILTER UNIT Fig 4 The received signal 15 connected directly into the RF filter unit compartment 1 of the turret assembly The filter unit contains eight band pass filters with pass bands as follows FLI 0 to 2 MHz FL 6 to 9 MHz FL2 2 to 3 MHz FL6 9 to 14 MHz FL3 to 4 MHz FLT 14 to 21 MHz FLA 4 to 6 MHz FL8 21 to 30 MHz When the MEGAHERTZ control is set to the MHz of the required frequency the filter appropriate to that frequency is automatically selecte
62. ial connectors are mated correctly If the receiver is to be sed on a desk fit the four feet to the case or tf it 18 to mounted a rack or cabinet fit the mounting brackets Surt able screws with washers are provided for both methods of mounting When feet are to be fitted the screws securing the bottom cover are removed and the cover then secured in position by the feet securing screws Extension pillars are also provided to enable the receiver to be raised at the front if desired 2 1 2 Supply connections For mains operation the supply s connected into the receiver at PL1 on the rear panel using the mains socket provided Ihe connections to the socket are Pole neutral Pole 1 ne Pole earth For d c operation a floating 24V supply should be connected to the appropriately coded terminals of the terminal strip on the rear panel 2 1 3 Receiver terminations Apart from the PHONES jacks on the front panel other connections can be made at the sockets or the terminal strip on the rear panel these are all coded according to their use 2 2 SETTING UP 2 2 1 Power supply The equipment is normally despatched from the manufacturers with the mains transformer tappings wired for operation on 240V mains Should any other mains supply voltage be used change the connections and links to the transformer primary as shown below Ensure that terminals 5 and 6 D C and on the terminal strip on the rear pane
63. l 1 4kHz 1 4kHz 5 5 kHz Symmetrical 3 5kHz 3 5kHz 12 0 kHz Symmetrical 6 0kHz 6 0kHz 18 0 kHz Symmetrical 12 0kHz 12 0kHz 36 0 kHz Symmetrical CW 0 5 uV for 2098 signal noise ratio AM 2 5 uV for 10dB signal noise ratio SSB 0 5 uV for 10dB signal noise ratio Thirty bands of 1 MHz each with an 84 inch scale length for each band There is an overlap of 100 kHz at both ends of each band It is possible to set the tuning control to within plus and minus 10 Hz of a required frequency Not worse than plus and minus 500 Hz at any point in the 1 MHz band when correctly calibrated at mid band Marker at 100 kHz points provided from the master 1 MHz oscillator and BFO check Output constant within 3dB for approximately 15048 change in input level above A G C threshold of 0 5uV e m f Attack Decay Short 10 m s 100 m s Medium 10 m s 1 sec Long 10 m s 10 sec Variable 8 kHz with slow motion tuning and calibration facility Nominal 75 ohms Can accept without damage either signals up to 30 e m f of 15 mins duration with less than 1dB degradation in noise factor and 6V e m f continuously 100 kHz 50mV into 75 ohms Following IF selectively Internal Loudspeaker Two 600 ohm headphone outputs line balanced or unbalanced 150 or 600 ohm external 4 PR155C Audio O tput Level Noise Figure Audio Frequency Response Meter Indication IF Rejection Image Rejection Internally Generated
64. l are linked and that the mains and 22V fuses are of the correct rating for 200 to 2507 operation and for 100 to 125V operation Issue 4 12 155 5 TRANSFORMER TAPPINGS Jto DandGto B FtoAandGtoB JtoDandEtoK FtoAandEtoK JtoDandCtoH FtoAandCtoH To operate on 24V d c unearthed Supply connect this Supply between terminals 5 and 6 of the terminal strip having removed the link If the panel lamp is required to be used A C or D C operation link the terminals 3 and 4 PANEL LAMP 2 2 2 Link connections If the internal 1 MHz oscillator and VFO interpolating oscillator to be used set the INT 1 MHz and INT VFO links to the ON position but either or both is to be replaced with external oscillators set the relevant link to and inject the external oscillator output to the relevant socket on the rear panel Make the appropriate coaxial connections at the panel above the mains transformer as follows Internal oscillators in use cable T to cable 26 cable 28 to termination External 1 MHz oscillator in use cable 28 to cable 24 External VFO in use cable 7 to cable 25 Set the LINE OUTPUT IMPEDANCE link to the position appropriate to the impedance required Issue 5 13 PR155 2 2 3 External connections Connect the aerial to the AERIAL socket and if external oscillators are to be used they should be similarly connected to the sockets provided on the rear pa
65. lace the locking response as near as possible to the centre of the sweep i e compromise RV1 to 4 on wafer E so positioned that only the one to be adjusted can be reached Reset MHz selector to 13 and 14 in turn adjusting RV2 on wafer E for optimum f Reset MHz selector to 5 and 6 MHz in turn adjusting RV3 on wafer E for optimum waveform 1 t2 Diagram b Diagram b __ WAVEFORM CLIPPED ON 45 LINE Reset MHz selector to 2 MHz and adjust RVA on wafer E for optimum waveform Diagram c Lock R71 to 4 on wafer E and RV on koard J Diagram 2 h Reset receiver to 29 MHz and observe sweep waveform and ensure that it 18 symmetrical about the locking response Set the receiver to each megacycle in turn down to O checking that the sweep waveform goes either side of the locking response by satisfactory margin PR155 Un 3 5 3 Reconnect pin 2 on modules Je Set the MEGAHERTZ control to O the oscilloscope trace should be a horizontal line and the frequency measured on the counter should be 37 500 MHz Rotate the MEGAHERTZ control to each of its other positions in turn and at each position verify that the frequency is 1 MHz higher than at the previous position the local oscillator does not lock at a particular position RV3 on board J may be slightly readjusted to make it lock Should it be necessary to adjust RV3 verify that the oscillator looks
66. nced line or the unbalanced line output terminal 5 18 4 Meter Amplifier The meter amplifier board provides circuits for the following functions 1 Audio Output Level adjustments 2 AGC Threshold adjustment 3 Provision of RE IF Gain control voltage The audio input is applied at terminal 9 via H1 and C1 to rectifier D1 The d c is routed via RV1 and terminals 1 amp 6 to the amplifier VT1 the amplified Issue 1 24 PR155C voltage being applied to the meter via terminal 3 RV1 is used to adjust the audio output to the required level The AGC voltage is applied via terminal 4 to H2 and thence via terminals 5 amp 6 to the amplifier VT1 The AGC threshold level is adjusted by RV3 which sets the level of VT1 emitter The voltage is read at the meter via terminal Zener 03 provides 12V at terminal 7 for the RF IF gain voltage which is applied to modules via the RF IF gain control RV1 The AF RF selector switoh selects terminals 1 or 5 of the board RV2 is the meter shunt and D4 D5 provide temperature compensation for the network R8 R9 R10 D3 PR155C 241 Issue 1 4 SERVICING 4 1 GENERAL The information provided in this section is designed to assist in location of a fault to a particular module of sub assembly and enable adjustment of certain preset controls using items of standard commercial test equipment 4 2 TEST EQUIPMENT Test equipment as detailed below is required for the tests delailed in
67. nel Make the necessary line output connections at the terminal block on the rear panel 2 3 OPERATION 2 3 1 Normal operation Set the receiver controls as follows Mode selector switch to the mode of operation required BANDWIDTH switch to the required bandwidth AGC to 0 1 sec position for tuning to 1 10 Sec position when on tune The 0 1 sec position may be used when on tune if rapid signal fading is experienced to O AUDIO GAIN to mid position RF IF GAIN initially fully clockwise Meter switch to RF Set the control switch to STANDBY and allow 10 minutes for the oscillators to stabilize Switch to ON Turn the MEGAHERTZ control until the megahertz portion of the frequency required 18 shown in the window Turn the RF IF GAIN anti clockw1se until the background noise in the speaker or headphones is reduced to tolerable level Bofore selecting the kilohertz portion of the required frequency first check the calibration of this portion of the film scale at the nearest 100 kHz point in the manner described in para 2 3 2 The required frequency can then be tuned by rotating the main tuning control until the kilohertz portion is indicated on the KILOHERTZ film soale If required set the SLOW FAST SLOW control to SLOW and tune for maximum indication of the signal to be received using the tuning meter Adjust the AUDIO GAIN control for optimum level in the phones or loudspeaker If operating on CW adjust t
68. nuation The control circuit is prevented from responding to transient changes in signal level by capacitor C24 The output from VT4 is applied via R19 to the second variable attenuator circuit and via C13 to the first mixer The line from module 8 is applied to a control amplifier VT5 and VT6 This operates in similar way to VT9 and VT10 as VT6 draws more current via D4 so the out put signal is attenuated to maintain an output of approximately 30 mV to prevent overloading of the first mixer Threshold adjustment is obtained by iyusting RV1 approximately 150uV e m f input signal FIRST MIXER MODULE 2 Fig 6 The signal input to module 2 is applied via a 30 MHz low pass filter C1 to C7 and L1 to L3 to transformer T1 and the first local oscillator signal is applied to transformer T2 Transformers T1 and T are connected with diodes D1 to in ring bridge mixer configuration the output from which at the first IF of 37 3 MHz is filtered by the 37 3 MHz bandpass filter PL1 and applied to the first IF amplifier in module 4 When the control switch 51 on the front panel is set to CALIBRATE markers at 100 kHz intervals throughout the frequency range are applied in place of the signal input for calibration of the receiver Under these conditions the 15V supply to module 1 is switched off at 51 3 4 FIRST LOCAL OSCILLATOR MODULE 3 Fig 7 The first local oscillator is a free running oscillator employ ing
69. oltmeter Adjust RV1 on module 7 for a reading of 78 to 83mV r m s Lock RV1 i Should a reading of 78 to 83mV not be obtainable a fault in module 11 or the selected bandwidth filter is indicated Module 11 tests are detailed in 4 11 2 A fault in the filter can be verified by repeating the test with the BANDWIDTH switch set to 3 5 kHz ii If satisfactory results are obtained remove the input reconnect cable 13 and proceed Issue 1 26 PR155C c Modules 4 and 10 Break cable 11 joining modules 2 and 4 and inject an unmodulated 37 3 MHz signal at an EMF of 1 5uV into module 4 Tune the input signal for maximum indication on the valve voltmeter By adjustment of RV1 on module 4 through the module handle set the output to 73 to 80mV r m s 1 If 15 18 not possible to obtain the necessary output then a fault in module 4 or module 10 is indicated Module 10 testing is detailed in 4 11 3 ii If satisfactory results are obtained lock RV1 remove ihe input and proceed d Modules 2 and 3 Terminate cable 11 from module 2 with a 75 ohm resistive load and connect valve voltmeter across the load Break cable 10 connecting modules 1 and 2 and inject an unmodulated 1 MHz signal at an EMF of 100mV into module 2 Tune the receiver for maximum indication on the valve volt meter indication of not less than 15mV should be obtained i If 15mV output is not obtainable fault is indicated in module 2 or the fir
70. ontrol The drive to the interpolating oscillator tuning protrudes through one end of the module and is coupled via an Oldham coupler to the KILOHERTZ film scale drive 1 4 BRIEF TECHNICAL DESCRIPTION See Fig 2 Three stages of frequency conversion are used in the receiver the intermediate frequencies being 27 5 MHz 10 7 MHz and 100 kHz The receiver signal is filtered in one of eight sub octave bandpass filters in turret compartment 1 the filter appropriate to the signal frequency being selected by the setting of the MEGAHERTZ control After filtering the signal is amplified in amp wideband amplifier module 1 This amplifier incor porates gain control loop which enables it to accept signal amplitudes in excess of 17 and at the same time maintain an output level compatible with minimum cross modulation and intermodulation products The RF amplifier output is applied to the 1st mixer module 2 in which it is mixed with the signal from the 1st local oscillator module 3 for conversion to the 18 IF of 37 3 MHz The 1st local oscillator covers the frequency range 37 3 to 67 3 MHz free running oscillator capable of being tuned to any frequency within the range is used and tuning is effected by amp phase look control loop spectrum generator module 10 provides signals at each MHz from 55 MHz to 64 MHz and signals for interpolation between these to achiefe the required local oscillator frequency are produced by an interpol
71. opriate to the bandwidth required AGC switch 84 The switch 54 has four positions these being OFF 0 1 sec 1 0 sec and 10 sec In the OFF position the 15V supply to the main AGC amplifier is removed and the receiver gain is controlled by RVi the RP IF gain control RV1 may be used as amp threshold control when the AGC is set to any of the operating positions The 1 0 sec and 10 sec decay times are controlled by amp shaper board which linearises the characteristic The 0 1 sec decay time is primarily intended for tuning purposes Other switches The loudspeaker ON OFF switch 5 is used to isolate the loudspeaker when it is not required dummy load R6 is connected in place of the loud Speaker when 55 is at OFF to maintain the loading of the audio amplifier and prevent the level at the PHONES jacks from rising For metering purposes the AGC line and the audio output are connected via a resistor and a rectifier diode to poles of the meter switch 56 the required rectified signal is selected by 96 and applied to the meter M1 5 18 5 Selector links Selector links on the receiver rear panel are provided to enable the required line output impedance to be selected and in order that the internal oscillators may be disabled when external oscillators are to be used The line output impedance selector link is used to connect an appropriate resistor R2 or a link in series with the line output transformer bala
72. or inputs the difference frequency element of their outputs is cancelled out when they are connected together whilst the sum frequency elements are added Thus amp signal whose frequency is the sum of the two input frequencies is obtained at RVi slider Adjustment of RV1 enables any difference frequency resulting from inequality of the difference frequency out puts from the modulators to be cancelled out The sum frequency output from RV1 is applied as a synthesized local oscillator frequency via emitter follower VT8 to board 5 8 5 Phase detector Board H Fig 12 The first local oscillator signal from the isolating amplifier is transformer coupled via T1 to the base of VT and thence via and T2 to VT3 base Transformers T1 and T2 are connected to provide 2 to 1 step up ratio 3 drives transformer T to provide reference signal at the local oscillator frequency to the phase detector diodes D1 to D4 to turn the diodes on and off on alternate half cyoles Issue 1 18 PR155C The synthesized frequency output at the required local oscillator frequency is applied via a high pass filter circuit to the base of and the amplified output from collector is coupled via emitter follower to second amplifier VT6 whose output is limited by the clipping diodes D5 and D6 and applied via two emitter followers VI5 and VT4 to the phase detector When the two inputs to the phase detector are in quadrature ze
73. quisite securing screws and washers Protection circuits are incorporated in the PH155B which will enable continuous RF input signal of up to 6V EMF to be accepted without causing damage The input circuit is arranged to match to 75 ohm unbalanced aerial system The audio outputs available are two 600 ohm outputs suitable for operation of headsets and 150 ohm and 600 ohm balanced or unbalanced external line output n internal loudspeaker is fitted The a c version of the equipment is designed to operate from a 100 to 125V or 200 to 250V 48 to 420 Hz single phase supply or an unearthed d c supply of 24V Its power consumption is approximately 18W at 24V or 35VA at 240V 50 Hz A d c version for operation on 24V d c earthed supply is available 1 2 MECHANICAL DESCRIPTION 1 2 1 General The PR155B is of modular construction consisting of fifteen standard modules assembled together on a main chassis assembly Apart from RF connections which are made with individual coaxial connectors all connections between the modules and the ohassis are made via the chassis wiring 1 2 2 Main Chassis The main chassis with modules and sub assemblies in position is illustrated in fig 1 Eleven of the modules are located in screened compartments above the main member of the chassis and connect with the chassis wiring via soldered contacts on the underside of the chassis Pin contacts on the modules are soldered to contacts which are m
74. ro out put is obtained and the output rises to maximum in one polarity when the signals are of the same frequency and exactly in phase and in the other polarity when they are exactly anti phase The output from the detector is integrated by R8 C5 and then applied to the amplifier on board J 5 8 4 D C Amplifier and reactor swee enerator Board J Fig sweep voltage whose mean level is variable according to the setting of the MEGAHERTZ control is generated by multivibrator in order to sweep the first local oscillator through the required frequency The multivibrator employs transistors VT8 and VT9 whose collectors are returned to earth via tapping on the resistance chain on wafer E of turret compartment 2 to control the mean level of the output from collector The amplitude of the output from VT9 collector can be preset by adjustment of RV2 The square wave voltage at the collector of VT9 is integrated by R21 C4 to produce an approximation to a sawtooth waveform This sawtooth is applied to the base of VT6 which operates with VT5 in a differ ential amplifier circuit Assuming no input to VT5 base the sweep waveform appears at its collector and is directly coupled to VI7 base controlling the emitter current This current is drawn via one winding of the saturable reactor in the first local oscillator sweeping the local oscillator frequency about the required frequency Transistors VI1 and VT are connected as a differen
75. rs transistors etc is available under part number 630 1G 14375 Note 5 1 MAIN CHASSIS 630 1 14974 523 Resistors spp 11 10 i Erie 16 403 4 78168 081 5 10 i Erie 16 405 4 18168 301 6 5 Erie 108 403 4 78183 247 10 10 Erie 16 403 4 78168 233 14 10 i Erie 16 403 4 78168 061 15 5 1 Erie 402 4 18251 029 Capacitors 25 402 4 01 201 001 439 8 53808 032 Plessey Electrolytic Electrolytic Plessey Electrolytic Dubilier 660M Mullard C280 Erie Ceramicon 439 1 14441 011 400 4 98474 017 400 4 98268 007 400 4 98260 007 PR155C Potentiometer 1k ohm Lin 404 1 02650 154 Potentiometer 5k ohm 20 Log 404 1 02650 296 Transistor 0035 Mullard 411 4 98108 002 Filter Composite 422 8 00100 001 Switoh 408 1 00004 005 Switch 408 1 00002 083 Switch 408 8 00004 007 Switch S P D T 408 4 98084 006 Switch D P D T 408 4 98084 010 Transformer 407 8 22047 Transformer 55 401 4 980 55 issue 1 Loudspeaker CP DN Fuse Link Size 00 1754 1A 518 4 98000 006 Fuse Link Size 00 1754 24 1157 Fuse Link Size 00 1562 2 54 518 4 98004 007 Box spanner 5242 Buck and Hickman 630 4 17437 Plug electrical fixed 3 pin Mk 4 508 1 40061 320 Socket jack with black facia nut 511 4 98041 005 Instrument indicating 682 4 99011 Choke 407 8 21965 Choke 407 8 21959 Lamp 14 volt 0 75 watt L E S 517 4 98028 Plug el
76. s linear Transistor VI1 operates in a tunable oscillator circuit in which 11 is the variable component Linearity of tuning is achieved in manufacture by adjustment of individual turns of 11 coil and final trimming is provided by L2 and CT The output from VT1 emitter is coupled via an emitter to follower buffer stage 2 to an amplifying stage VI3 and the amplified output is fed to turret compartment 3 3 8 via a second emitter follower VT4 Output amplitude is adjusted by RV1 to a nominal 400mV r m s The d c supply to the oscillator and buffer stage is stabilised to 10V by zener diode D1 PR155C 17 Issue 1 3 7 MHz SELECTOR TURRET COMPARTMENT 2 Fig 10 The MHz selector circuit selects the required megahertz output from the spectrum generator module 10 for mixing with the output of the interpolating oscillator The circuit employed is identical in operation to that of the 48 MHz selector in module 10 3 5 but the tuning coils 11 and 12 in module 10 are selected in pairs from 30 pairs according to the settins of the MEGAHERTZ control to enable each megahertz output from 35 to 64 MHz from the spectrum generator to be selected The output from this compartment of the turret is applied to the phase lock loop circuits in compartment 5 The d c supply is locally stabilised at 10V by zener diode 22 5 8 PHASE LOCK CIRCUITS TURRET COMPARTMENT 5 5 8 1 General In the phase lock loop circuits contained in compartment 5 of the
77. scale and verify by use of the frequency counter that the frequency at cable 8 is tunable by means of the receiver tuning over the range 38 2 to 39 4 MHz f Set the MEGAHERTZ control to 29 MHz and verify that the output frequency is capable of being tuned over the range 66 2 to 67 4 MHzo Failure to obtain satisfactory results in b c or d would indicate that module 3 is unserviceable but failure in e or f may indicate a faulty module 3 a fault in phase lock circuit testing as detailed in 4 12 4 11 2 10 6 10 8 MHz oscillator module 11 To test the 10 6 10 8 MHz oscillator proceed follows a Break cable 15 module 11 to module 5 and terminate the cable from module 11 with 75 ohm resistive load Connect frequency counter across the load b Select USB at the mode selector switch The frequency as measured on the counter should be 10 800000 MHz c Replace the counter with a valve voltmeter The meter should indicate not less than 100mV reme Se d Select LSB or and repeat d and c The frequency should be 10 600 MHz and the meter indication 100mV r m s 4 11 3 Spectrum generator module 10 and MHz selector The 1 MHz oscillator in module 10 can best be eliminated as faulty by using an external MHz oscillator see 2 2 2 However if suitable oscillator is not available break cable 23 module 10 to module 12 and measure the frequency on a counter at the cable from module 10 it
78. should be 1 00000 MHz C19 may be adjusted for this condition Replace the counter with 75 ohm resistive load and measure the output across the load it should be not less than 400mV The 48 MHz output from module 10 can be measured across 75 ohm resistive load connected across cable 12 from the module an output of not less than 400mV at 48 MHz should be obtained PR155 31 Issue 5 Note In making this test it may be found that the high 1 MHz content of the output may affect the operation of the frequency counter It is therefore advisable to use a 75 ohm stepped attenuator the resistive load and to set the attenuator to give minimum operative input to the counter Operation of the spectrum generator at all other frequencies can best be checked in conjunction with the MHz selector circuits in turret compartment as detailed in 4 11 4 4 11 4 Megacycle selector turret compartment 2 Verify correct operation of the megacycle selector circuit as follows Remove the bottom cover of the turret Locate the MHz input connection on board G in compartment 3 fig 1 and connect it to the input of the frequency counter via coaxial connector b Switch on the PR155 and set the MEGAHERTZ control to O Verify that the frequency indicated is 35 MHz 866 Note in 4 11 3 c Repeat b for each turret position verifying that the output frequency increases by 1 MHz at each successive setting of the MEGAHERTZ control to
79. signal across C5 is rectified and amplified and the resultant d c voltage applied to the base of and further amplified Diodes 25 D4 D5 and 815 provide two stage rise time circuit The first portion of the signal rise causes the diodes to conduct heavily but as the voltage across C8 approaches that of the signal the diodes will switch off R13 and RV2 control the rise time at the leading edge of the signal thus preventing instability whilst not affecting the overall rise time VI7 VIS and VT9 are emitter followers the IF gain control is applied to the base of 9 and controls the level VI5 and VT6 provide overshoot limiting and noise pulse projection should the signal rise sharply D2 will conduct and charge up C6 The sudden rise will cause the AGC to cut off the front end of the receiver and thus no signal will appear at the emitter of VT5 at this instance C6 will discharge and cause VT6 to conduct and feed a signal back into the circuit When the AGC is switched off the 15V to VT9 is removed and therefore there will be no AGC outputs the gain being set by the RF IF gain control D7 and D8 in the absence of a signal prevent C8 from discharging to below 3 3 volts 3 14 AUDIO AMPLIFIERS MODULE 9 Fig 19 Two audio amplifiers are contained in module 9 one feeding the PHONES jacks and the internal speaker is on board A and the other providing the line outputs is on board B Both boards are supplied with
80. st local oscillator circuits see 4 11 1 ii If satisfactory result is obtained reconnect cable 11 and proceed e Module 1 Terminate cable 10 from module 1 with a 75 ohm resistive load and connect a valve voltmeter across the load Break cable 3 connecting module 1 to the turret and inject an unmodulated 1 MHz signal at an EMF of 1mV into module 1 Tune the input for maximum indication on the valve voltmeters this indication should be not less than 5mV Unsatisfactory results indicate a fault in module 1 4 5 2 Final Test If satisfactory results are obtained in all of the stage gain tests repeat dede 4 6 a Should the overall gain still be unsatisfactory a fault in the filter turret compartment or the aerial input circuit is indicated b If the overall gain is s ghtly high adjust RV1 on module 4 to obtain the correct overall gain when she receiver is tuned to 15 MHz PRODUCT DETECTOR AND LINE AMPLIFIER Test the product detector and line amplifier gain in the manner detailed below CH Connect a 600 ohm load between the 600 ohm output terminals on the rear panel and connect a valve voltmeter across the load Set the selector link on the rear panel for 600 ohms output Set the AGC to 0 1 secs the MODE to PR155 21 Issue 5 CW and the BANDWIDTH to 300 Hz Apply a 15 MHz signal at 0 5uV and tune the receiver to give maximum output from the 100 kHz IF Aagust the BFO to give a 1 kHz
81. tial amplifier in which the total current drawn is maintained constant at level controlled by VT2 and determined by the setting of RV3 the voltage across RV3 being clamped by zener diode D1 Balance of the amplifier is preset by the setting of RV1 to give equal collector voltages The output from the phase detector board H is applied between the transistor bases but VI3 base is clamped by D1 Thus antiphase voltages are developed at the two collectors when the local oscillator frequency is the same as the synthesized frequency obtained from board H The amplitudes of these outputs are affected by the transistor characteristics and are not necessarily equal the most suitable output is selected by the setting of a link in manufacturing tests The selected output is coupled to the base of emitter follower VI4 and the voltage developed at VT4 emitter is connected to D1 and D2 in the first local oscillator to provide a fine control of oscillator frequency The emitter of VT4 is also directly coupled to VT5 base to oppose the sweep voltages at VI6 base and thus maintain a constant current through VI7 i e through the saturable reactor To summarize the sweep voltage sweeps the local oscillator towards the frequency required when this frequency is equal to the synthesized frequency a voltage is developed to provide accurate tuning and at the same time the reactor current is clamped at the value appropriate to this frequency Thus the local oscill
82. ting of RV2 in VT3 base circuit 3 15 100 kHz DIVIDE AND CALIBRATE CIRCUIT MODULE 12 Fig 20 Module 12 contains the circuits which from a 1 MHz input from module 10 or an external oscillator produce the 100 kHz required for carrier reinsertion on S 8 B and the 100 kHz markers used for receiver calibration Issue 1 22 PH155C The 100 kHz output is derived from divide by ten integrated circuit 1 The 4 7 volt required by ML is obtained from the zener diode Li via R24 The 1 MHz input is amplified and limited by VT1 and coupled to pin 1 by the common collector stage VT2 The output of ML1 is taken from pin 12 as a Square wave and fed via the low pass filter Lo and to the 8 8 B detector circuits module 7 and via C8 to the base of the calibrate amplifier VT3 Following amplification in VT the signal is clipped by D3 differentiated and then injected into the first mixer when CALIBRATE is selected at S1 for calibration purposes 3 16 B F 0 Fig 21 The BFO is energised when the mode selector switch 52 is set to CW It consists of an oscillator stage VI1 followed by an emitter follower VT2 which feeds the oscillator output to the product detector in module 7 via 82 for operation The oscillator operates at a nominal 100 kHz and is tunable by 8 kHz about 100 kHz by means of the front panel BFO control C9 The output amplitude is adjustable by means of the preset control RV1 3 17 ISOLATING AMPLI
83. ty of damage in the event of reversed polarity of the input since correct polarity of the input to the regulator is ensured by The output from the regulator at 15V d c is connected to the common pole of S1AF 3 18 2 Switching circuits Control Switch 51 When 51 is set to STANDBY 15V is connected via S1AF to the 1 MHz oscillator in module 10 and to the interpolating oscillator only at the same time the output of the calibrate circuit in module 12 is earthed In the ON position of 81 the receiver is operational and all circuits with the exception of the calibrate circuit in module 12 are supplied with 15 When 51 is moved to PR155C 25 Issue 1 CALIBRATE the 15V supply to module 1 is broken at 51 the output from module 12 calibrate circuit is applied via S1AB to module 2 and the calibrate circuit is supplied with 15 via Mode selector switch 92 Wafer S2AF switches the 15V supply to the oscillators in module 11 to energise the relevant circuit for USB or other modes of operation Module 12 is supplied with 015V via S2AB on USB or LSB operation and the BFO is similarly supplied on CW operation The 15V supply is switched to the relevant detector circuit in module 7 via S2BF The fourth wafer S2BB is sued to switch either the 100 kHz output from module 12 or the 0 output to module 7 on SSB or CW operation respectively BANDWIDTH switch 25 This switch is used to select the filter appr

Service Manual for the PR155B MF/HF

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