TG501 Service Manual - Iss 5
Contents
1. 27106 0621 27106 0621 27106 0621 27106 0621 27106 0621 27106 0604 27106 0604 27106 0604 27164 0600 27106 0604 27106 0604 27254 0010 27223 0740 27223 0000 27223 0000 27220 0000 27164 0504 27106 0604 27106 0604 27106 0506 27160 0009 27 28 Description Switchbank Switchbank Button black Button grey Stud 3mm x 10mmL for pot bracket Track pins Vero pins LV AC from transformer TP12 TP14 to 22 inc Transistor pad for Q23 30 31 Heatsink TOS for Q23 30 31 Header 2 Way TP1 to TP11 inc TP13 Zero ohm resistors LK1 to LK69 inc J1 J2 J3 amp J4 Socket IC 8 pin Socket IC 14 pin Socket IC 16 pin Bracket potentiometer for VR27 Spindle extension for VR27 Washer shakeproof M3 for pot bracket Wahser M3 for pcb bracket Nut M3 for pot bracket 2 for pcb bracket 2 PCB Support bracket Screw M3 x 8mmL for pcb bracket Adhesive pad for C51 C52 Terminal for T1 PCB Main TG501 2 3 12 Way 7 Way 13 off 6 off 2 off 16 off 12 off 3 off 3 off 12 off 73 off 13 off 6 off 2 off 2 off 4 off 2 off 2 off 4 off 3 off Part No 22225 0540 22225 0550 37113 0130 37113 0140 20205 0610 22469 0502 22469 0200 20661 0801 20670 0040 22573 0041 23185 0000 22574 0118 22574 0119 22574 0120 33141 0540 23347 0720 20037 0301 20030 0203 20210 0101 20663 0010 20234 0012 10300 0313 35311 0020 35555 0510 Front Panel Assy TG501 Description Front Panel TG5012. Dial single scale Washer PTFE for dial Knob black for dial Cap for dial knob Knob push on Cap for knob Pot 25KJ WW VR8 Pot 10KM CP VR1 Nut for VR1 Washer for VR1 Pot 1KOM CF VR11 Pot 10KM CF VR29 Pot 4700MM VR27 BNC Socket Bushing BNC insulating LED Adhesive pad for LED Sleeve for LED wire Solder tag shakeproof for earth wire Rear Panel Assy TG501 Description Rear Panel AC Mains Receptacle Shroud for receptacle Fuseholder Shroud for fuseholder Fuse 200mA slow blow for 220 240V input Fuse 400mA slow blow for 110 120V input Switch rocker Connector shrouded push on for switch Transformer T1 Spacer M4 x 15mmL for T1 Screw M4 x 45mmL for T1 Washer shakeproof M4 for T1 Nut M4 for T1 or 4 off 4 off 4 off 8 off 4 off 4 off 4 off 8 off 5 off Part No 33331 0710 37571 0060 31122 0220 20657 0020 20657 0021 20657 0001 20657 0009 23356 0010 23348 0010 23348 0700 23348 0701 23347 0029 23347 0030 23347 0110 22588 0004 22588 0700 25061 0200 10300 0313 10232 0303 20037 0400 Part No 33331 0820 22520 0120 22458 0004 22300 0210 22458 0001 22315 0227 22315 0236 22219 0030 22454 0030 22115 0040 20661 0224 20234 0030 20037 0304 20210 0102 29 Case 30 Description Screw M3 x 10mmL Washer shakeproof M3 for Mains skt Washer M3 for Mains skt Nut M3 Mains skt Screw M4 x 8mmL for Mains earth Solder tag shakepro
3. MF 3K3J W25 CF 220RJ W25 CF 1KOJ W25 CF 1KOJ W25 CF 3K3J W25 CF 4K7J W25 CF 1K0J W25 CF Part No 23187 4130 23185 3820 23185 3470 23185 3220 23185 3470 23185 1470 23185 3100 23185 1560 23185 1470 23185 1560 23185 1470 23185 2470 23185 0470 23185 0470 23185 2330 23185 0100 23185 0470 23185 0470 23185 2330 23185 0100 23185 0100 23185 0100 23183 1100 23183 1100 23202 0619 23202 1249 23202 0619 23202 0619 23202 0619 23202 1121 23202 1124 23185 2330 23185 1220 23185 2100 23185 2100 23185 2330 23185 2470 23185 2100 Ref R142 R143 R144 R145 R146 R147 R148 R149 R150 R151 R152 R153 R154 R155 R156 R157 R158 R159 R160 R161 R162 R163 R164 R165 R166 R167 R168 R169 R170 R171 R35 was fitted in series with R36 C11 on pre issue 5 pcbs Description 3K3J W25 CF 220RJ W25 CF 1KOJ W25 CF 4K7J W25 CF 1K2J W25 CF 8K2J W25 CF 5K6F W25 MF 10KF W25 MF 10KF W25 MF 4K7J W25 CF 10KJ W25 CF 4K7J W25 CF 10KF W25 MF 10KF W25 MF 22KJ W25 CF 8K2J W25 CF 3K9J W25 CF 1K8J W25 CF 2K2J W25 CF ZERO OHM ZERO OHM ZERO OHM ZERO OHM ZERO OHM ZERO OHM 22KJ W25 CF 22KJ W25 CF 100RJ W25 CF 6K8J W25 CF 10RJ W25 CF Part No 23185 2330 23185 1220 23185 2100 23185 2470 23185 2120 23187 2820 23202 2560 23202 3100 23202 3100 23185 2470 23185 3100 23185 2470 23202 3100 23202 3100 23185 3220 23185 2820 23185 2390 23185 2180 23185 2220 23185 0000 23185 0000 23185 0000 23
4. going triangle slope The triangle amplifier has unity gain and buffers the triangle wave on the multiplier capacitor to drive the comparator and output circuits The comparator operates as a window detector with fixed limit points set to the triangle peaks One of its two outputs drives the TTL circuit and is also level shifted to drive the diode gate The other output drives the squarewave shaper When the comparator output to the diode gate is high the triangle wave is positive going until this reaches approximately 1 2V the comparator output then switches low When the comparator output is low the triangle wave is negative going until this reaches approximately 1 2V when the comparator output goes high and the cycle is repeated This is the basic function generator loop in the Run mode and is shown by the double arrows in the block diagram Triangle and squarewave are generated simultaneously as shown The control logic determines Trig Gate or Run modes In Trig or Gate modes the waveform is clamped by the 21 current sources and the diode gate at a point determined by the Start Stop Phase control A signal applied to Trig In releases the clamp and a single cycle is produced in the Trig mode or a burst in the Gate mode the waveform is then clamped again To achieve the 1 10 and 100 ranges the 1k range capacitor is multiplied by 1000 100 or 10 by the capacitor multiplier circuit The TTL circuit buffers one of the comparator outputs
5. therefore minimum sinewave distortion VR23 adjusts the dc operating point of the sinewave convertor to give symmetrical operation on both positive and negative halves of the waveform VR20 adjusts the dc output of the convertor and VR21 output amplitude Output Preamplifier The selected waveform passes to the preamplifier Q20 and Q21 form a long tailed pair and are in thermal contact with each other to reduce dc drift Q22 and Q23 are two cascaded emitter followers feedback is via R98 The preamplifier is an inverting virtual earth type DC offset is trimmed by VR26 Sine square and triangle waveform amplitudes are set for 10V peak to peak into 50 Ohm at the 50 Ohm output by VR21 VR24 and VR25 respectively 11 Output Amplifier and DC Offset 12 b Pla La 32 21025 y 4 4 aj o LI NM x CH T K A ru es SH A Reale uJ tH y U fig a fig b The signal passes via the Amplitude control VR27 to the output amplifier A simplified diagram is shown in fig 7 and the following circuit description refers to this The HF amplifier is made up of discrete components and is in principle an inverting operational amplifier with a gain of 10 set by R109 and R115 This has offset voltages and currents which are compensated for by IC19 and IC20 IC19 compensates for input bias currents IC20 controls dc offset and LF gain by driving the non inverting input Refer now to fig
6. 185 0000 23185 0000 23185 0000 23185 3220 23185 3220 23185 2100 23185 2680 23185 0100 21 22 Ref VR2 VR3 VR4 VR5 VR6 VR7 VRQ VR10 VR12 VR13 VR14 VR15 VR16 VR17 VR18 VR19 VR20 VR21 VR22 VR23 VR24 VR25 VR26 VR27 VR28 VR30 VR31 VR32 VR33 VR34 Description Preset 22K Preset 10K Preset 10K Preset 10K Preset 10K Preset 10K Preset 220R Preset 10K Preset 10K Preset 10K Preset 10K Preset 1K0 Preset 10K Preset 470R Preset 4K7 Preset 100R Preset 2K2 Preset 100R Preset 4K7 Preset 10K Preset 1K0 Preset 1K0 Preset 22K Pot 470R Lin Preset 10K Preset 22K Preset 10K Preset 2K2 Preset 2K2 Preset 2K2 Part No 23377 3220 23377 3100 23377 3100 23377 3100 23377 3100 23377 3100 23377 1220 23377 3100 23377 3100 23377 3100 23377 3100 23377 2100 23377 3100 23377 1470 23377 2470 23377 1100 23377 2220 23377 1100 23377 2470 23377 3100 23377 2100 23377 2100 23377 3220 23347 0110 23377 3100 23377 3220 23377 3100 23377 2220 23377 2220 23377 2220 R142 was 4K7 on pre issue 5 pcbs Ref C1 C2 C3 C4 C5 C6 C7 C8 C9 C10 C11 C12 C13 C14 C15 C16 C17 C18 C19 C20 C21 C22 C23 C24 C25 C26 C27 C28 C29 C30 C31 C32 C33 C34 C35 Description 10NZ 63V Cer 10NZ 63V Cer 10NZ 63V Cer 10NZ 63V Cer 150PF 630V P S 1N8F 160V P S 82PK 30V P S 22NG 100V P E 220NG 100V P E 100NJ 100V P E 4N7K 63V Cer 10NZ 63V Cer 10NZ 63V Cer 10NZ 63V Cer 10NZ 63V Cer 47PG 63V
7. 2 The triangle wave is amplified by IC11 which has a gain of 3 this is trimmed by VR15 to set the overall gain of the capacitance multiplier Q8 and Q9 buffer the output of IC12 The triangle buffer consists of a FET source follower Q10 with temperature compensation provided by current source Q11 which is Ipss matched with Q10 Q13 and Q14 are emitter followers to provide 2 low impedance outputs O12 is strapped as a diode and compensates for the VBES of Q13 and Q14 VR17 trims the DC offset in this stage Waveform Generation Comparator and TTL output poi TA rh L las P p A DV J ss LL r U r f Ru ec ko los feo len fh pe ges R E ZE H AL La rd i Ll el h 1 Ge We Ju 8 aa gm be Us H nu L TG ose e ake CHE E Mass so T LET AI Ue ez pe g Boe Tam y 2117 E ai MAU cc IC13 operates as a window detector and determines the peak to peak amplitude of the triangle wave on the range multiplier capacitor which is approximately 1 2V C17 C22 compensate for comparator and loop delays ensuring that the triangle wave amplitude remains constant with increase in frequency The two internal NAND gates in IC13 are wired as a flip flop to ensure positive switching of the comparator C23 provides a small amount of positive feedback to ensure jitter free operation Some comparators oscillate with the dial at 0 005 this can be prevented by fitting C66 One of the comp
8. 2100 23185 1100 23185 0100 23202 3100 23185 3220 23202 4100 23202 5100 23185 3100 23185 0100 Parts List 17 18 Ref R34 R35 R36 R37 R38 R39 R40 R41 R42 R43 R44 R45 R46 R47 R48 R49 R50 R51 R52 R53 R54 R55 R56 R57 R58 R59 R60 R61 R62 R63 R64 R65 R66 R67 R68 Description 10RJ W25 CF 100RJ W25 CF 1K0J W25 CF 10KJ W25 CF 470RJ W25 CF 220RJ W25 CF 1K5J W25 CF 1K5J W25 CF 820RJ W25 CF 1K0J W25 CF 1K2J W25 CF 100RJ W25 CF 330RJ W25 CF 14K3F W25 MF 220RF W25 CF 681RF W25 MF 124RF W25 MF 124RF W25 MF 681RF W25 MF 220RF W25 MF 14K3F W25 MF 150RJ W25 CF 1K0J W25 CF 1K8J W25 CF 3K0J W25 CF 4K7J W25 CF 1K8J W25 CF 3KOJ W25 CF 2K2J W25 CF 2K2J W25 CF 1K2J W25 CF 4K7J W25 CF 4K7J W25 CF 4K7J W25 CF 4K7J W25 CF Part No 23185 0100 23185 1100 23185 2100 23185 3100 23185 1470 23185 1220 23185 2150 23185 2150 23185 1820 23185 2100 23185 2120 23185 1100 23185 1330 23202 3143 23185 1220 23202 1681 23202 1124 23202 1124 23202 1681 23202 1220 23202 3143 23185 1150 23185 2100 23185 2180 23187 2300 23185 2470 23185 2180 23187 2300 23185 2220 23185 2220 23185 2120 23185 2470 23185 2470 23185 2470 23185 2470 Ref R69 R70 R71 R72 R73 R74 R75 R76 R77 R78 R79 R80 R81 R82 R83 R84 R85 R86 R87 R88 R89 R90 R91 R92 R93 R94 R95 R96 R97 R98 R99 R100 R101 R102 R103 Description 4K7J W25 CF 4K7J W25 CF 2K2J W25 CF 1K5J W25 CF 33KJ W25 CF 2K2J W
9. 23594 0219 23594 0231 23438 0007 23438 0007 23594 0219 23594 0219 23438 0007 23438 0007 23557 0244 23557 0244 23438 0007 23427 0322 23427 0322 23557 0650 23427 0325 23557 0650 23427 0325 23557 0650 23557 0650 23427 0310 23427 0325 23427 0325 23427 0325 23427 0325 23427 0524 23427 0347 23984 0001 23984 0001 Ref D1 D2 D3 D4 D5 D6 D7 D8 D9 D10 D11 D12 D13 D14 D15 D16 D17 D18 D19 D20 D21 D22 D23 D24 D25 D26 D27 D28 D29 D30 Description Dio 1N4148 Dio 1N4148 Dio 1N4148 Dio 1N4148 Dio 1N4148 Dio 1N4148 Dio 1N4148 Dio 1N4148 Dio 1N4148 Dio 1N4148 Dio 1N4148 Dio 1N4148 Dio 1N4148 Dio BZX79C11 Dio BZX79C11 Dio 1N4148 Dio 1N4148 Dio 1N4148 Dio BZX83C11 Dio BZX83C11 Dio 1N821 Dio 1N4002 Dio 1N4002 Dio 1N4002 Dio 1N4002 Dio 1N4148 Dio BZX83C5V6 Dio 1N4148 Dio 1N4148 Dio 1N4148 Part No 25021 0901 25021 0901 25021 0901 25021 0901 25021 0901 25021 0901 25021 0901 25021 0901 25021 0901 25021 0901 25021 0901 25021 0901 25021 0901 25130 0910 25130 0910 25021 0901 25021 0901 25021 0901 25130 0908 25130 0908 25130 0226 25115 0907 25115 0907 25115 0907 25115 0907 25021 0901 25130 0217 25021 0901 25021 0901 25021 0901 C66 is optional See circuit diagram 25 26 Ref Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9 Q10 Q11 Q12 Q13 Q14 Q15 Q16 Q17 Q18 Q19 Q20 Q21 Q22 Q23 Q24 Q25 Q26 Q27 Q28 Q29 Q30 Q31 Q32 Q33 Q34 Q35 Description Tra
10. 25 CF 100RJ W25 CF 47RJ W25 CF 7K5J W25 CF 560RJ W25 CF 100RJ W25 CF 7K5J W25 CF 91RJ W25 CF 7K5J W25 CF 7K5J W25 CF 68RJ W25 CF 7K5J W25 CF 100RJ W25 CF 47RJ W25 CF 10KJ W25 CF 5K6F W25 MF 5K6F W25 MF 220RJ W25 CF 470RJ W25 CF 1K8J W25 CF 270KJ W25 CF 150RJ W25 CF 6K2J W25 CF 6K2J W25 CF 2K2J W25 CF 3K6J W25 CF 3K3J W25 CF 680RJ W50 CF 10RJ W25 CF 22RJ W25 CF Part No 23185 2470 23185 2470 23185 2220 23185 2150 23185 3330 23185 2220 23185 1100 23185 0470 23187 2750 23185 1560 23185 1100 23187 2750 23187 0910 23187 2750 23187 2750 23185 0680 23187 2750 23185 1100 23185 0470 23185 3100 23202 2560 23202 2560 23185 1220 23185 1470 23185 2180 23185 4270 23185 1150 23187 2620 23185 2620 23185 2220 23187 2360 23185 2330 23179 1680 23185 0100 23185 0220 19 20 Ref R104 R105 R106 R107 R108 R109 R110 R111 R112 R113 R114 R115 R116 R117 R118 R119 R120 R121 R122 R123 R124 R125 R126 R127 R128 R129 R130 R131 R132 R133 R134 R135 R136 R137 R138 R139 R140 R141 Description 130KJ W25 CF 82KJ W25 CF 47KJ W25 CF 22KJ W25 CF 47KJ W25 CF 470RJ W25 CF 10KJ W25 CF 560RJ W25 CF 470RJ W25 CF 560RJ W25 CF 470RJ W25 CF 4K7J W25 CF 47RJ W25 CF 47RJ W25 CF 3K3J W25 CF 10RJ W25 CF 47RJ W25 CF 47RJ W25 CF 3K3J W25 CF 10RJ W25 CF 10RJ W25 CF 10RJ W25 CF 100RJ 1W CF 100RJ 1W CF 61R9F W25 MF 249RF W25 MF 61R9F W25 MF 61R9F W25 MF 249RF W25 MF 121RF W25 MF 124RF W25
11. 8 for the description of the HF amplifier simplified Q24 and Q26 are complementary emitter followers to provide low drive impedance to the complementary class A amplifier stage Q28 and Q29 Level shifting is achieved by adjustable zener diodes these are formed by a zener diode and a VBE multiplier Note incorrect setting of the level shifters will cause excessive current to flow in the class A stage causing damage to these devices Refer to the calibration section for adjustment procedure The output of the amplifier stage is buffered by complementary emitter followers Q30 and Q31 to drive the 50 Ohm output D17 and D18 provide their bias The non inverting input is effectively the emitters of the class A amplifier D19 and D20 provide the necessary level shifting Calibration N j Le Te a S v NA Cs Cs 1 S rA v e LS 71 Fi VR J gt AN eg K L NH p A pam C2 NM 12 s s Y d Ly Calibration diagram Eguipment Reguired Oscilloscope Distortion meter 4 5 digit battery powered multimeter Calibration should be carried out after the instrument has been on for 1 hour Note If any work has been done to the output stage VR32 and VR33 must be turned fully anti clockwise before switching on The available calibration points are Dial calibration high frequency 5 0 end 10k range
12. Cer 18PG 63V Cer 22PG 63V Cer 82PG 63V Cer 82PG 63V Cer 3N3F 160V P S 3N3F 160V P S 10PC 63V Cer 10NZ 63V Cer 10NZ 63V Cer 10NZ 63V Cer 22PG 63V Cer 270PG 63V Cer 10NZ 63V Cer 68PG 63V Cer 100NS 63V Cer 2P2C 50V Cer 10NZ 63V Cer 10NZ 63V Cer 100NS 63V Cer Part No 23427 0325 23427 0325 23427 0325 23427 0325 23647 0515 23646 0009 23646 0708 23620 0805 23620 0804 23620 0207 23427 0346 23427 0325 23427 0325 23427 0325 23427 0325 23427 0329 23427 0337 23427 0323 23427 0349 23427 0349 23646 0007 23646 0007 23427 0328 23427 0325 23427 0325 23427 0325 23427 0323 23427 0347 23427 0325 23427 0332 23438 0007 23427 0524 23427 0325 23427 0325 23438 0007 23 24 Ref C36 C37 C38 C39 C40 C41 C42 C43 C44 C45 C46 C47 C48 C49 C50 C51 C52 C53 C54 C55 C56 C57 C58 C59 C60 C61 C62 C63 C64 C65 C66 C67 VC1 VC2 Description 100NS 63V Cer Not used 100NJ 100V P E 1NOK 63V Cer 0 47UF 35V Tant 10UF 16V Tant 10UF 16V Tant 0 47UF 35V Tant 100NS 63V Cer 100NS 63V Cer 10UF 16V Tant 10UF 16V Tant 100NS 63V Cer 100NS 63V Cer 1000UF 63V Elec 1000UF 63V Elec 100NS 63V Cer 100PG 63V Cer 100PG 63V Cer 100UF 25V Elec 10NZ 63V Cer 100UF 25V Elec 10NZ 63V Cer 100UF 25V Elec 100UF 25V Elec 1P8C 63V Cer 10NZ 63V Cer 10NZ 63V Cer 10NZ 63V Cer 10NZ 63V Cer 2P2C 50V Cer 270PG 63V Cer 4 64pF Poly P 4 64pF Poly P Part No 23438 0007 23620 0207 23427 0331 23594 0231 23594 0219
13. MATCHED PAIR BF245A Q20 AND Q21 ARE IN THERMAL CONTACT DIODES ARE 1N4148 UNLESS OTHERWISE SPECIFIED ALL SWITCHES ARE SHOWN IN THE OUT POSITION IF IC 13 OSCILLATES WITH THE DIAL AT 005 FIT C66 BET R83 7K5 7K5 15V 5V w Poo R46 MAN TRIG SW ov 1 3 1c15c O 4 1C164 74L 500 15V see note 1 R21 x1M x100K x10K x1K x100 x 10 x1 SW8__SW7 SW6 SW5 SW SW3 C5 ce C7 y c9 SE 2 1 150p VO o 82p ov 65p 1 01 96 7 see note 1 911 gt 2 2 2 2 5 Ze 59 1 Sy gt gt a gt loja I TTL R24 VR15 DN R54 14K3 1 OPTIONAL SEE NOTE 5 R132 B 249 R131 R133 R134 61R9 121 124 OV 6 o son o E SW17 SW16 20dB 048 VR27 470 AMPLI TUDE R103 22 R117 47 15V s 15V PA 15V PA R118 R119 1c22 PA 3K3 10 46 5V o FS1 rr 400 MAT 120V 200 ZA N lt A ON OFF CHASSIS 04 10V 928 N 10 2N3906 Hz D17 D19 R126 nV i TP17 15V 931 VR29 5 Ai D18 D20 2N2905A 10K R104 nv wv DC OFFSETL swis e EA 130K Spy Ech d R125 LED 101 OWER us R105 TK8 82K 15V PA 15V PA
14. TG501 Function Generator Service Manual TT Book Part Number 48591 0130 Issue 5 Table of Contents General 1 Specification 2 Functional Description 4 Circuit Descriptions 6 Calibration 13 Parts List 17 General Service Handling Precautions Service work should only be carried out by skilled engineers Please note that the tracks on the printed circuit board are very fine and may lift if subjected to excessive heat Use only a miniature temperature controlled soldering iron and remove all solder with solder wick or suction before attempting to remove a component Dismantling the Instrument WARNING Opening the instrument is likely to expose live parts The instrument shall be disconnected from all voltage sources before any adjustment replacement or maintenance and repair during which it shall be opened If afterwards any adjustment maintenance or repair of the opened instrument under voltage is inevitable it shall be carried out only by a skilled person who is aware of the hazards involved 1 Remove the 8 side screws and lift off the case upper and lower 2 Access to all components is now possible further dismantling is not necessary 3 All small knobs are push on types To remove the dial remove the cap in the centre of the knob using a knife blade then loosen the nut about 1 turn The knob and dial can then be pulled off 4 Transistors Q32 Q34 and Q39 and IC22 are insulated from the rear panel 5 Reas
15. Trig and Gate modes The ramp can only stop in the upward direction When the Q output of IC14b is set low D1 is off If the voltage at Q5 emitter is OV to 0 the voltage on the range capacitor will ramp up and stop at OV When clamped the I current from the diode bridge flows through the diode between pins 4 and 3 into the 21 current sink A current equivalent to I also flows through the diode between pins 9 and 1 into the 21 current sink to total 21 IC7 and Q5 buffer the voltage on the Start Stop Phase control VR11 to give a low impedance voltage source on pin 9 of IC10 This voltage can be varied between approximately 1 2V by VR11 corresponding to the triangle peaks giving 90 of phase control To release the clamp the Q output of IC 14b is set high which pulls the 21 current sink high via D1 reverse biasing the two clamp diodes Waveform Generation range selection and triangle amplifier Range selection is by seven push button switches which steer the current sources into the appropriate multiplier capacitor The lower four ranges use the same range capacitor C9 the lower three ranges use a Capacitance multiplier The capacitance multiplier steals current from the range capacitor via R36 The amount of current taken is determined by the gain setting resistors R28 R30 or R31 for the x100 x10 and x1 ranges respectively The triangle wave on C9 is connected to the non inverting inputs of IC11 and IC1
16. VR3 Dial calibration low frequency end 005 VR2 Waveform symmetry high frequency end of dial 5 0 VR9 Waveform symmetry at the low frequency end of dial 005 is affected by offset nulling of ICs 2 to 6 see below Dial calibration 1M range VC1 Dial calibration 100k range VC2 Capacitance multiplier offset VR16 Capacitance multiplier gain VR15 DC offset of triangle amplifier VR17 Sinewave distortion VR18 VR19 VR22 and VR23 Sinewave dc offset VR20 13 14 Sinewave amplitude VR21 Squarewave amplitude VR24 Triangle wave amplitude VR25 DC offset of preamplifier VR26 Output amplifier quiescent operating current VR32 and VR33 Output amplifier dc offset VR31 Output amplifier bias compensation VR28 Output amplifier LF gain VR30 15Vrail VR34 For best results the above adjustments should be carried out in the following manner After the instrument has warmed up the case upper is removed to make any adjustments which should be done in a draft free environment Adjust VR34 for 15 0V 100mV at TP12 Check 15V rail is within 2 of the 15V rail at TP18 Check 10V rail is 10 2 400mV at TP19 Check 10V rail is within 2 of the 10V rail at TP21 Check 5V rail is 5 0V 0 25V Check 5V rail is 5 0V 0 25V Select Run 1k range dial at 5 0 dc offset out sguarewave OdB Offset nulling of ICs 1 to 6 is critical for correct operation of the instrument Gold plated t
17. arator outputs is routed via lC 17a to parallel gates IC17 c and d which drive the TTL output O15 level shifts IC13 output to be about ground to drive the diode gates O16 is a VBE multiplier and its total voltage is just under two Vers R45 R46 and C16 improve triangle linearity at 5MHz IC15a and level shifter O17 are used to drive the squarewave shaper circuit When the sguarewave button is out pin 4 of IC15a is held low and so the sguarewave is gated off at the source Waveform Generation Trigger Circuit 10 In the Trig or Gate modes the waveform is clamped at the Start Stop Phase point under control of IC14b described earlier Q19 and IC15b form a Schmitt trigger which ensures correct operation from DC to 5MHz R71 and R72 with C27 fix the input threshold at lt 1 5V over the whole frequency range In the trigger mode the output of IC15b is routed through IC15c and IC16a to the monostable formed by IC16b and c For every high going transition at the trigger input or depression of the manual button a 50 nanosecond pulse at IC16c output is generated This pulse goes from high to low and back to high after 50ns and is used to set the flip flop IC14b which releases the waveform clamp The flip flop now waits for a rising edge on its clock input this occurs when the triangle wave changes from a negative slope to a positive slope This edge resets the flip flop and enables the waveform clamp circuit which stops the wave
18. ative end of C50 or positive end of C51 The 17V supply is connected to the positive end of C50 and the 17V supply is connected to the negative end of C51 Typical current drain from the 17V supply with output at minimum is 200mA and 240mA Input power with 240V input 90mA maximum This service manual specifically covers issue 5 pcbs Pre issue 5 boards have the following differences R35 100R was fitted in series with R36 C11 and not in the sinewave converter R142 was 4K7 pcb support brackets were not fitted PCB Assembly Main Ref R1 R2 R3 R4 R5 R6 R7 R8 R9 R10 R11 R12 R13 R14 R15 R16 R17 R18 R19 R20 R21 R22 R23 R24 R25 R26 R27 R28 R29 R30 R31 R32 R33 Description 10RJ W25 CF 150KJ W25 CF 43KJ W25 CF 10KJ W25 CF 39KJ W25 CF 2K7F W25 MF 2K7F W25 MF 2K43F W25 MF 1K37F W25 MF 1K37F W25 MF 2K32F W25 MF 750RF W25 MF 4K3J W25 CF 4K3J W25 CF 750RF W25 MF 3K3J W25 CF 47RJ W25 CF 47RJ W25 CF 2K7F W25 MF 2K7F W25 MF 47RJ W25 CF 47RJ W25 CF 374RF W25 MF 1K5J W25 CF 1K0J W25 CF 100RJ W25 CF 10RJ W25 CF 10KF W25 MF 22KJ W25 CF 100KF W25 MF 1MOF W25 MF 10KJ W25 CF 10RJ W25 CF Part No 23185 0100 23185 4150 23187 3430 23185 3100 23185 3390 23202 2270 23202 2270 23202 2243 23202 2137 23202 2137 23202 2232 23202 1750 23187 2430 23187 2430 23202 1750 23185 2330 23185 0470 23185 0470 23202 2270 23202 2270 23185 0470 23185 0470 23202 1374 23185 2150 23185
19. est pins are provided and a gold plated 2 way header on the end of the leads to the DVM is recommended to make a good connection and help to avoid thermal e m f s IC TP Adjust DVM Reading 1 13 VR4 lt 40uV 2 1 VR lt 40uV 3 2 VR6 lt 40uV 4 3 VR7 lt 40uV 5 4 VR10 lt 40uV 6 5 VR12 lt 40uV 8 6 VR13 lt 100uV H 7 VR14 lt 100uV 12 10 VR16 lt 100uV Nulling of the triangle amplifier is achieved by shorting its input TP11 and adjusting VR17 to give lt 2mV at TP9 To null the pre amplifier deselect the waveform output by releasing the 3 function buttons Connect a DVM to the right hand leg of the amplitude control VR27 and adjust VR26 for lt 3mV Output stage adjustment must be carried out with great care to avoid circuit damage Adjustment is easiest with 2 voltmeters one connected to TP15 and the other to TP14 With only one meter available alternately monitor the 2 test points With no output waveform selected and the amplitude control at minimum slowly adjust VR32 and VR33 for 13 4V to 13 5V at the two test points Note that the voltage on these test points TP14 and TP15 must not go below 13 3V otherwise Q28 and Q29 will be damaged VR32 and VR33 are interactive Connect a DVM to TP16 and check that the voltage on this point is lt 1V If not slightly adjust VR32 or VR33 ensuring that the voltages on TP14 and TP15 remain within 13 4V to 13 5V Note that it may be nece
20. form at a point determined by the Start Stop Phase control In the gate mode the monostable around IC16b and c is disabled and the signal bypasses IC16b When a high level signal is applied to Trig in the output of IC16c goes low and releases the waveform clamp The generator now free runs until the Trig in signal goes low and IC16c output goes high IC14b flip flop now waits for a rising edge on its clock input as in trigger mode and stops In the run mode IC14b flip flop is permanently set by SW9b disabling the waveform clamp so that the generator free runs Waveform Generation Waveform Shaping The squarewave shaper is a diode bridge which steers current from either R89 or R90 into R91 This provides a squarewave with controlled rise fall times and thus no overshoot and ringing which is symmetrical about ground The drive signal comes from Q17 The sine shaper comprises a monolithic transistor array IC18 which is driven by the triangle amplifier The circuit has two non linear stages A pair of emitter followers round the peaks of the triangle which are adjusted by VR18 for the bottom of the waveform and VR22 for the top of the waveform The output from this stage is impressed across R78 and R81 in series and applied to the second stage This comprises a long tailed pair driven almost into cut off and converts the clipped triangle wave into a sinewave VR19 adjusts the gain of the long tailed pair to bring them close to cut off and
21. ks and VR23 to give a symmetrical display Note this is not minimum on the distortion meter do not adjust these two presets to give minimum distortion at this stage correct My incorrect AAA din ef 15 Now slowly adjust VR18 and VR22 to remove these peaks Check the distortion meter reading which should now be less than 0 5 typically 0 3 If not very slightly adjust the above 4 presets to achieve this If the instrument fails to meet specification check the following amplitude linearity and symmetry of triangle wave at TP9 pre and output amplifiers Adjust VR20 to trim dc output of the sinewave converter measured on the oscilloscope or use a DVM connected to the 50 Ohm output TP 17 Adjust VR21 to give 10 2V peak to peak into 50 Ohm Triangle amplitude adjust VR25 to give 10 2V peak to peak into 50 Ohm Squarewave amplitude ajust VR24 to give 10 2V peak to peak into 50 Ohm Servicing Notes 16 The white printing on the pcb also shows all the points which are top soldered The circles teardrops show track pins and the squares show which lead of a component is top soldered Insulating washers are fitted to IC22 Q32 Q34 and Q39 Heatsink compound is applied to regulators IC22 Q32 Q34 and Q39 and between transistor pair Q20 and Q21 To help with trouble shooting the power supply etc an external current limited 500mA power supply of 17V can be used with its ground OV going to the TG501 ground neg
22. lead 37541 0490 Mains Lead tinned ends or 22491 0010 Mains lead Euro plug or 22491 0020 Mains lead USA plug 22491 0040 Guarantee Card 48581 0230 Instruction Book 48591 0100 Parts Changes From September 1988 a new case with changed cosmetics was introduced This consisted of a different case upper and lower front and rear panels side support brackets and the use of case bezels to front and rear The front panel earth wire connection by the shakeproof solder tag was no longer required Anew carton was also introduced to accomodate the new case The old and new parts which are not interchangeable are as follows Old Parts Description Part No Case Upper 33537 0240 Case Lower 33537 0250 Front Panel 33331 0710 Rear Panel 33331 0820 Side Bracket 2 off 31547 0140 Solder tag shakeproof 20037 0400 Carton 38114 0100 Load spreader for carton 38114 0105 End Cap for carton 2 off 20664 0170 New Parts Description Part No Case Upper 33537 0500 Case Upper 33537 0510 Front Panel 33331 1400 Rear Panel 33331 1410 Side Bracket 2 off 31547 0290 Bezel Case 2 off 31711 0050 Carton 38114 0150 Load spreader for carton 38114 0155 End Cap for carton 2 off 20664 0200 31 0V 0 1 Hov 0 2 5V O 3 HEN O 4 5V O 5 15V O6 ov O7 P2 O8 ov 09 P3 010 ov O11 P7 O12 DN 013 Pi 014 DN 015 P6 O16 R171 SWEEP IN QL R3 43K 15V FREQUENCY DIAL R2 NOTES Q10 AND Q11 ARE A
23. n ZTX239 Tran ZTX214 Tran ZTX214 Tran ZTX239 Tran ZTX239 Tran ZTX214 Tran ZTX239 Tran ZTX239 Tran ZTX214 Tran BF245A Tran BF245A Tran ZTX214 Tran ZTX214 Tran ZTX214 Tran 2N3904 Tran ZTX239 Tran 2N3904 Tran 2N3904 Tran ZTX313 Tran 2N3904 Tran 2N3904 Tran 2N3904 Tran 2N2219A Tran 2N3906 Tran ZTX239 Tran 2N3904 Tran ZTX239 Tran 2N3906 Tran 2N3904 Tran 2N2219A Tran 2N2905A Tran BD240 Tran ZTX214 Tran BD240 Tran 2N3904 Part No 25380 0229 25341 0214 25341 0214 25380 0229 25380 0229 25341 0214 25380 0229 25380 0229 25341 0214 25601 0103 25601 0103 25341 0214 25341 0214 25341 0214 25381 0404 25380 0229 25381 0404 25381 0404 25380 0230 25381 0404 25381 0404 25381 0404 25377 0700 25341 0218 25380 0229 25381 0404 25380 0229 25341 0218 25381 0404 25377 0700 25344 0500 25344 0020 25341 0214 25344 0020 25381 0404 Ref Q36 Q37 Q38 Q39 Q40 Q41 Q10 amp Q11 are matched devices Ref IC1 IC2 IC3 IC4 IC5 IC6 IC7 IC8 ICQ IC10 IC11 IC12 IC13 IC14 IC15 IC16 IC17 IC18 IC19 IC20 IC21 IC22 Description Tran 2N3904 Tran 2N3906 Tran 2N3906 Tran BD239 Tran BC338 Tran ZTX550 Description LF441CN LF441CN LF441CN LF441CN LF441CN LF441CN TLO71CP TLO71CP TLO71CP CA3019 TLO71CP TLO71CP NE521N 74LS74 74LS00 74LS00 7400 CA3127E TLO71CP TLO71CP LM324N LM340T 5 Part No 25381 0404 25341 0218 25341 0218 25382 0500 25383 0505 25341 0215 Part No 27106 0621
24. nuously at the selected frequency for duration of gate signal starting and stopping at the phase set by the START STOP PHASE control Last waveform started is completed Manual Manually operates generator as described in Triggered and Gated sections Start Stop Phase The START STOP PHASE control varies the triggered and gated signal start stop point from approximately 90 to 90 up to 500kHz Symmetry When SYM is selected the SYMMETRY control varies the duty cycle from 1 19 to 19 1 to produce sawtooth and variable pulse width waveforms The indicated frequency is divided by 10 with SYM selected INPUTS Sweep Input Input Impedance Input Sensitivity Maximum Allowable Input Voltage Sweep Linearity Maximum Slew Rate of Input Voltage Trigger Input Frequency Range Signal Range Minimum Pulse Width Input Impedance OUTPUTS 50 Ohm Amplitude Control Attenuator DC Offset Control Range TTL Amplitude GENERAL Power Requirements Input Voltage Power Consumption Environmental Operating Range Storage Temperature Range Size Weight 10kOhm 0 to 4V for 1000 1 sweep 10V Better than 1 0 1V us DC 5MHz TTL compatible levels maximum input 20V 50ns Typically 2kOhm gt 20dB vernier control within each attenuator range Maximum output 20V peak to peak from 50Ohm 10V into 500hm Additional switch selectable attenu ation of O 20 or 40dB Minimum output lt 20mV peak to
25. of 4BA for earth wires Washer insulating TO220 for Q32 34 39 amp IC22 Screw M3 x 8mmL nylon for Q32 34 39 8 1C22 Nut M3 nylon for Q32 34 39 8 1C22 Label On Off Label Serial No Parts Description Case Upper Case Lower Bracket side Screw M3 x 8mmL mushroom head case upper lower to side brackets Screw M3 x 5mmL Taptite PCB securing Washer M3 PCB securing Screw M3 x 10mmL Rear panel securing Washer M3 shakeproof Front amp Rear Panel securing Nut M3 Front amp Rear Panel securing Foot swivel Bracket foot pair Foot PVC black Hardware for all feet securing Screw M4 x 12mml Nut M4 Washer M5 Washer shakeproof Cable tie Spring foot silver bar Black feet pair 2 off 2 off 2 off 2 off 2 off 4 off 4 off 4 off 2 off 8 off 4 off 4 off 4 off 12 off 8 off 2 Off 4 off 4 off 2 off 4 off 4 off Part No 20234 0011 20037 0301 20030 0263 20210 0101 20234 0023 20037 0401 20613 0006 20224 0200 20210 0200 37511 0340 37558 0460 Part No 33537 0240 33537 0250 31547 0140 20237 0001 20062 0500 20030 0263 20234 0011 20037 0301 20210 0101 20662 0200 20662 0201 20662 0520 20234 0029 20210 0102 20030 0267 20037 0304 20653 0204 33171 0130 20662 0201 Packaging Parts Description Part No Carton TG501 38114 0100 Load spreader for carton 38114 0105 End Cap for carton 2 off 20664 0170 Label wiring instructions for tinned ends Mains
26. peak from 50Ohm lt 10mV into 500hm 10V from 500hm DC offset plus signal peak limited to 10V 5V into 500hm DC offset plus waveform attenuated proportionally in 20dB and 40dB positions Fixed TTL level output at frequency and symmetry of main output Capable of driving 20 TTL loads 110 120V AC nominal 50 60Hz or 220 240V AC nominal 50 60Hz adjustable internally The TG501 will operate safely and meet specification within normal AC supply variations viz 100 130V AC and 200 260V AC respectively 30VA Max 50C to 400C 20 to 80 RH 400C to 700C 300mm wide x 100mm high x 230mm deep 3 4kg Functional Description The relationships between the major circuit elements are shown in the block diagram opposite The summing amplifier sums the voltages from the dial and from the sweep input and its output controls the magnitude of the complementary current source and current sink This current varies from approximately 5 2uA to 5 2mA for a 1000 1 frequency change 005 5 0 The symmetry control adjusts the ratio between current source and current sink The diode gate steers current into or out of the range multiplier capacitor and is controlled by the comparator output When the comparator output is high the charge on the capacitor will rise linearly producing the positive going triangle slope When the comparator output is low the charge on the capacitor will fall linearly producing the negative
27. plifier is approximately 4mV with the dial at 005 to 4V with the dial at 5 0 This voltage is used to drive the complementary current source and current sink as follows The emitter of Q1 is held at pseudo ground by IC2 If the dial is at 5 0 the 4V at the output of IC1 is forced at the emitter of Q2 by IC4 This 4V is also halved by R6 R7 and IC3 forces this voltage 2V at the junction of R9 R10 Avoltage dependant current is therefore set up through R8 R9 R10 and R11 IC5 is a current source controlled by the voltage on the collector of Q1 and IC6 is a current sink controlled by the voltage on the collector of Q2 These two currents are steered into and out of the range capacitor by the diode gate IC10 under the control of the comparator output When the symmetry button is depressed the short across VR8 is removed and the total resistance between Q1 and Q2 emitters is increased from R to 10R This lowers the current through this resistor chain by a factor of 10 and so the frequency is divided by 10 Rotating VR8 imbalances the current through Q1 and Q2 to give a duty cycle of up to 1 19 or 19 1 With the symmetry button out the waveform symmetry is set by VRQ at the top of dial 5 0 At the bottom of the dail symmetry is determined by offsets on ICs 1 6 refer to calibration procedure Current source IC8 tracks the I current source IC5 and IC9 mirrors this to become 21 The 21 current is used to clamp the waveform in the
28. protective earth terminal is likely to make the instrument dangerous Intentional interruption is prohibited Power Supply DC Regulation Diodes D22 to D25 rectify the transformer output and C50 and C51 are the reservoir capacitors of the unregulated DC rails Q34 Q35 Q36 and IC21a form the 15V regulator Q34 and Q35 form the compound series pass element and Q36 its driver IC21a is the error amplifier and a temperature compensated zener D21 provides the reference 6V2 The 15V output is set by VR34 The 15V regulator is made up of Q37 Q38 Q39 and IC21b and complements the 15V regulator The 15V tracks the 15V by sensing the voltage at the junction of R149 R150 at the input of IC21b The 10V rail is derived by dividing down the 15V rail R151 and R152 provide the reference from the 15V for the regulator IC21c and Q40 The 10V regulator is formed by Q41 and IC21d and is the complement of the 10V regulator The 10V tracks the 10V by sensing the voltage at the junction of R154 R155 at the input of IC21d The 5V rail uses a standard 3 terminal regulator IC22 The 5V rail is divided down from the 15V by R139 R140 and buffered by a darlington emitter follower Q32 and Q33 Waveform Generation Summing Amplifier and Current Sources d HST The dial and sweep voltages are summed by IC1 the gain of which is set by VR3 VR3 is in fact used to calibrate the high end of the dial The output range of the am
29. semble in reverse order Operating Voltage See the Power Supply section for details of changing the operating voltage from 220 240 to 110 120 and vice versa Specification All specifications apply after warm up in an ambient temperature range 180C 280C OPERATING RANGE Frequency Range 005Hz to 5MHz in 7 overlapping decade ranges with fine adjustmentby calibrated vernier Internal Mode Vernier Range 1000 1 within each range Vernier Accuracy Better than 5 of full scale External Sweep Mode Sweep Range 1000 1 within each range FUNCTIONS Specifications apply for vernier between 0 5 and 5 0 and output 10V peak to peak into 50Ohm termination Sine Distortion Less than 0 5 to 50kHz less than 1 to 500kHz all harmonics gt 30dB below fundamental on 1M range Amplitude Flatness 0 2dB to 500kHz 1dB to 5MHz Triangle Linearity Better than 99 to 500kHz Squarewave Rise and Fall Times lt 45ns Mark Space Ratio 1 1 11 to 100kHz 5 to 5MHz DC Range 10V from 50 Ohm OPERATING MODES Run Generator runs continuously at the selected frequency Triggered Generator is quiescent until triggered by an external input at TRIG IN or by pressing MANUAL One complete cycle is then generated at the selected frequency starting and stopping at the phase set by the START STOP PHASE control Gated Generator is quiescent until gated by an external signal at TRIG IN or by pressing MANUAL Generator then runs conti
30. ssary to add a low value resistor in the meter lead close to TP14 and TP15 to prevent instability in the amplifier Connect a voltmeter to TP8 and adjust VR28 for lt 1mV Connect a DVM to TP17 and adjust VR31 for lt 3mV Frequency multiplier to 100 range squarewave adjust VR30 for a flat top squarewave Note that the oscilloscope must be dc coupled for this adjustment Symmetry select 1k range and adjust VR9 for equal mark space ratio using the oscilloscope x10 X multiplier to increase resolution and the trigger slope switch Before commencing the vernier calibration procedure turn the dial fully clockwise and check that the 005 mark aligns with the mark on the front panel If not remove the cap in the centre of the knob using a knife blade and loosen the nut one to two turns The knob can now be slid around on its shaft to align the marks Tighten the nut and check that the dial rotates freely against the front panel Refit the knob cap On later instruments a PTFE thrust washer is fitted between the dial and the front panel Dial Multiplier Adjust Reading 5 0 10k VR3 49 5 to 50 5 kHz 5 0 1M VC 4 9to 5 1 MHz 5 0 100k VC2 490 to 510 kHz 5 0 100 VR15 495 to 505 Hz 0 005 100k VR2 465 to 475 Hz Sinewave distortion select sinewave 1k range dial at 5 0 Display the distortion meter output on CH2 of the oscilloscope Position VR18 and VR22 fully clockwise Adjust VR19 to give a flat response between pea
31. to drive the TTL output socket The squarewave shaper converts the comparator output to a current signal and applies it to the squarewave function switch The sinewave converter uses the non linear characteristics of a transistor pair to convert the triangle wave into a sinewave which is applied to the sinewave function switch The selected function is sent to the pre amplifier where it is inverted and buffered and applied to the output amplitude control The signal is summed with the voltage from the DC offset control at the output amplifier This amplifier inverts and amplifies the signal up to 20V peak to peak to drive the 50 Ohm output socket The power supply converts the incoming AC line voltage to the DC rails required by the instrument Circuit Descriptions Power Supply Mains connections The operating voltage of the instrument is shown on the rear panel label Should be it necessary to change the operating range from 220 240V AC to 110 120V or vice versa change the transformer connections following the appropriate diagram below 220 240V Operation Primaries in Series If a change is made the operating voltage label and fuse should also be changed For 220 240V operation use 200mA 250V time lag For 110 120V operation use 400mA 250V time lag 34 WARNING THIS INSTRUMENT MUST BE EARTHED Any interruption of the protective conductor inside or outside the instrument or disconnection of the
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