Service Manual
Contents
1. 10 hm Si Pur BH 19044197 Roas 18429 PNP Silicon BCBS SH13044107 Rea 73430 NPN 4912040022 Rest T 31 sitcom D137 382 Reso 411130005 T3432 Danington Matched Pair BOX65A 01 Reo Ed BOXGAA 0V MASO0 1 2801 111630087 rss 4113040964 aiia 15437 Bess Safety 4 7 ohm BM 4111130262 59136427 Rees 4111023027 Teese Rezo Carbon 41111023027 13440 2913040927 Bera Carbon Film 4911023027 18240 1712040092 neza 4111023027 NEN Silicon BESA 191304092 E Tsai NPN Suicon BcSaS 4913041001 24 Dartington Matched Pair 802674 4113041048 700 NPN Sitcon acssoc 1912041096 amnesinia Tseay Sticon Channel FET BF2450 2913041024 Broz Tsaa NEN Sec HE Stitesasis 4913040927 R707 Metal Film 332K rc 13450 E 4913049237 Metal F r 2 21e rci 1050605 18451 NPN Siicon acsas 4912040932 13 ELECTRICAL REPLACEMENT PARTS LIST Con t REF DESCRIPTION PartNo ner DESCRIPTION PART NO 272227232222 Tass epe Ms insulato2. 1912420624 5112474071 Movional Feedback AdjumA7K 4910110027 41113420875 Current Adjust High Prec Amp 12420475 410110064 4912120202 AC Power Switch 4127610564 412420475 1 41242082 Automatic Switch 4127010516 eut impedance Switch p 2912420200 4912420404 SEMICONDUCTORS 4912231026 4112420527 5413090812 4912140092 Dae 81113030204 4912221081 5465 513020813 5912424017 Dase 51113030011 4H12140461 54 913042206 4H12140463 5477 Doda 5913020012 Polyester 4H12140461 5472 Diese BAWO 91113020012 Polyester Film t matowe toov 44121404471 0473 5414030613 iec rolyti 16 mld iov 4112420467 Zener Diode BZN7O1C4V7 4 7 mid 03 V 1912420404 4 7 mid 83V 112420404 Daza Siicon Diode BAW62 5113020813 412420465 0477 Simcon Diode BAW62 5113020013 Electrolytic 10 412420096 Ligne Emiving Diode Leo cavaa 5912020613 Electrolytic 22 mf eav 4912420499 Daar Siicon Briag recono BY 64 5112020474 Electrolytic 2 x 2350 mfa 0482 Silicon ride Recnfier BY ioa 21112020414 Bridge BY 164 RESISTORS PNP 5113049197 15422 4912040941 peas Metal Pum 22 1 Tn Rear Metal Fim aa e A642 Metal 75425 Reas
3. which is exactly proportional to its acoustic output as long as the cone moves as a single rigid piston This requirement forms part of the reasoning behind the 500 Hz crossover point as above this frequency the cone will begin to move independently in small areas resulting in less correlation between central acceleration and acoustic output The signal developed by the PXE is fed to a comparator Circuit which derives a correction signal from any differences between the input signal and the woofer cone acceleration signal This correction signal is combined with the input signal and fed to the low frequency amplifier resulting in considerable reduction of distortion attributable to the loudspeaker and keeps the acoustic output virtually identi cal to the input signal waveform This is the principle of motional feedback CIRCUIT DESCRIPTION Before examining the individual circuits in detail it would be useful to know the construction of the acceleration transducer assembly As mentioned the Motional Feedback transducer is mounted under the dust cover in the apex of the woofer cone where it is in rigid mechanical contact with the voice coil assembly The transducer consists of a small printed circuit board containing the ceramic piezoelectric transducer and lated FET circuitry The mounting of the piezo tical It is held in place in a small hole in the PC board by two resilient rubber clamps allowing a calcu
4. The Main Board Heat Sink is hinged to the inside of the rear panel allowing it to swing away for easy access to ither side of the P C Board 4 To remove the Main Board Heat Sink from the rear panel lift it up and out of the hinge brackets 5 To reassemble the Main Board Heat Sink reverse the preceding steps Board side of ness to he rear Figure 5 Cabinet and Rear Panel Exploded View REF Fuse Holder 3 used DESCRIPTION AC inlet interlock Jack Assembiy Input Output AC Outer Channel Selector Switeh ISX 8 11 Bise Cam Input impedance Switch SK E 1V 19 Name Panel 4427610516 20 Geile Smali E rine argo 22 Locking Pin Holder 8 used 02504006 22 Locking Pin 8 used Krobw Gompression Spring 2 ured PART ana 1930673 331120520062 26240222 A SS Ag z E J d yin 00 Emp ne mas ges bee gor Figure 9 Stereo Cable Drawin
5. nel input will be amplified by that particular speaker assembly Fuse Holder fuse SB 250 IMPORTANT Take special care that the connections for fus Holder 15A 66 200V Left and Right on the control unit are not interchanged j High Frequency Roll Off Control This control allows you to choose the slope of roll off in dB per octave for 13 AC Inlet 117 Volts 60 Hz those frequencies above 7K Hz 14 AC Outlet 117 Volts 60 Hz 550 Watts Unswitched 7 Input Sensitivity Control This control allows you to match the speaker system to your amplifier or pre 15 Pilot Lamp LED on front panel This lamp when lit amplifier The control should be set for the output indicates that the speaker unit is completely operative voltage of the equipment being used to drive the speaker When the unit is in the standby condition or com system If the driving equipment is rated in watts RMS pletely off the indicator 500 s Figure 3 Front Panel Figure 2 Rear Panel DISASSEMBLY INSTRUCTIONS NOTE To insure proper reassembly replace each screw in the same location from which it was removed Chassis Access Refer to Figure 5 1 Remove the five screws securing the rear panel to the speaker enclosure These screws are designated by an 0 on the rear panel and an in Figure 5 2 The rear panel is hinged allowing it to swing away from the b
6. the Audio Input Jack located on the rear panel Place the Channel Selector Switch in the proper position to amplify the signal 3 Adjust R692 for 82 mV NOTE This adjustment must be made after replacing bass speaker woofer Is LS cd IC e E B 75722 Xx mp ORT E 1 nf 001 uf 10 nt 01 ut 100 nf Figure 10 S SES 08 gure 10 Schematic Diagram Es J EN KNEP N pro V ARCAM eve 4 EUER OUTPUT TRANSISTOR REPLACEMENT Since transformerless complementary symmetry push pull output circuitry is utilized in the motional feedback system extreme care should be exercised when servicing replacing the output transistors It is imperative that the transistor be isolated from the metal bracket by means of a mica insulator coated on both sides with Dow Corning DCA silicon grease or equivalent Before removal of an output transistor the type PNP or NPN should be noted to insure the identical replacement is reinserted into the same holes of the Board The outp
7. RH567 Motional Feedback System ServiceManual PHILIPS HIGH FIDELITY LABORATORIES LTD SERVICE DEPT P O BOX 2208 FORT WAYNE INDIANA 46801 PHILIPS 1 278 Copyright Philips High Fidelity Lat TABLE OF CONTENTS Description Technical Data General Description Circuit Description Operating Controls Jacks and Indicators Disassembly Instructions Cabinet Replacement Parts List Adjustments Output Transistor Replacement Electrical Replacement Parts List LIST OF ILLUSTRATIONS Figure Description 1 Block Diagram 2 E Rear Panel 3 Front Panel 4 Grille Removal 0 5 Cabinet and Rear Panel Exploded View 6 Wiring Diagram 7 Input Sensitivity Chart 8 Adapter Cable Drawing 9 Stereo Cable Drawing 10 Schematic Diagram ted Circuit Boards with Test Points and Basing Diagrams 12 Cable Chart 13 134 14 586 788 9810 11 amp 12 14 0 TECHNICAL DATA Gener Frequency Response 27 20 000 Hz Volume 30 litres 20 litres acoustic 1831 cu inches acoustic Loudspeakers AD10100 MFB 10 Woofer 00210 508 2 Dome Mid Range AD0140 T8 1 Dome Tweeter Power Supply 117 Volts 60 Hz Power Consumption Maximum 150 Watts Dimensions 320 x 540 x 265mm 13 x21 x 10 inches Tre
8. ack of the speaker enclosure Pull out on the right side of the rear panel to gain access to the chassis To completely remove the rear panel from the speaker enclosure disconnect Plug 4 from Socket 2 and lift the rear panel up and out of the hinge brackets To reassemble reverse the preceding steps making certain Plug 4 is inserted properly into Socket 2 This is accomplished by placing the referenced end of the plug adjacent to the referenced end of the socket LED Access Refer to Figure 5 1 Remove the three screws securing the Name Panel 19 to the front of the speaker assembly Then pull outward on the Name Panel to gain access to the LED 2 To reassemble reverse the preceding steps making certain the LED is properly positioned into the Name Panel 19 Speaker Access Refer to Figures 4 amp 5 1 Insert a table knife or similar dull edged tool between the Grille 20 21 and the speaker enclosure frame 2 Draw the Grille 20 or 21 forward while prying out ward with the tool The Grille is held to the speaker enclosure by friction snaps 3 To reassemble place the Grille 20 or 21 into position while aligning the snape Then press firmly at the corners Main PC Board Access Refer to Figure 5 1 Swing the rear panel away from the back of the speaker enclosure see Chassis Access 5 2 Remove the six screws securing the Main Board Heat Sink to the rear panel 3
9. ble Filter Continuously variable 0 18d8 Octave 3dB at 7 KHz Crossover Networks Electronic Crossover at 500 Hz Passive Crossover at 3500 Hz Connections Signal PHONO jacks 2 input 2 output AC inlet AC outlet unswitched Input Sensitivity Continuously variable 1 3 volts at 100K ohms 3 20 volts at 1K ohm Automatic On Off Switch Turn On time lt 1 second with an input signal 2 2mV Turn Off time gt 2 minutes Amplifiers Low Frequency Amplifier Minimum RMS Power 40 Watts RMS Bandwidth 35 Hz to 1000 Hz Maximum Total Harmonic Distortion 0 2 Load Impedance 4 ohms High Frequency Amplifier Minimum RMS Power 20 Watts RMS Bandwidth 400 Hz to 20 KHz Maximum Total Harmonic Distortion 0 2 Load Impedance ohms Subject to Modification 3 5 20 KHz Tow High amp Middle Frequency Amplifier 20W Figure 1 Block Diagram General Description The 667 is an electronic bi amplified three way loud speaker system employing the PHILIPS Motional Feedback MFB principle The enclosure which has a total volume of 30 liters incorporates three driver units an electronic regulator and control system and two power amplifiers one for the woofer and one for the mid range and tweeter The woofer low frequency amplifier is terminated in a 4 ohm load impedance and has a minimum continuous average sine wave RMS power of 40 watts The mid range tweeter
10. e must be paid in circuits with a band cally regulated TS455 TS456 The circuit also ensures width extending down to very low frequencies ee eee oo OPERATING CONTROLS JACKS AND INDICATORS Refer to Figures 2 and 3 1 Power Switch This is the main power switch and must rather than volts refer to Figure 7 be on for the unit to operate 8 Signal Input Jack Left Channel Receives the left 2 Automatic Switch With this switch off the unit func channel output signal from the driving equipment tions normally by using the Power Switch With the Automatic Switch and the Power Switch in the 9 Signal Input Jack Right Channel Receives the right position the unit operates on a standby basis Part of channel output signal from the driving equipment the power supply is energized at all times and the rest of the power supply energizes when a signal is applied to the 10 Signal Output Jack Left Channel Relays the left input unit When the signal is removed from the unit it will signal for feed thru hook up to other MFB return to the standby condition after a short delay To turn the unit off completely the Power Switch must be 11 Signal Output Jack Right Channel Relays the right inthe off position The pilot lamp LED is not lit in the input signal for feed thru hook up to other MFB standby or off condition Input Channel Selector Switch Determines which chan 3 Fuse Holder fuse 6 25ASB 125V
11. g ADJUSTMENTS IMPORTANT The amplifier circuitry should be allowed to warm up for 1 1 minutes to stabilize prior to final adjustments Low Frequency Amp Quiescent Current Adjustment To adjust the complementary symmetry push pull output stage of the low frequency amplifi 1 Switch the speaker system On and remove the audio input signal 2 Connect DVM across R670 and adjust R665 for 37 5 NOTE This adjustment must be performed when the low frequency amplifier output transistors are replaced Misadjustment may cause crossover distortion or possible Premature failure of the output transistors High Frequency Amp Quiescent Current Adjustment To adjust the complementary symmetry push pull output stage of the high frequency amplifier 1 Switch the speaker system On and remove the audio input signal 2 Connect a DVM across R727 and adjust R722 for 35mV NOTE This adjustment must be performed when the high frequency amplifier output transistors are replaced Mis adjustment may cause crossover distortion possible premature failure of the output transistors Motional Feedback Adjustment To adjust the amount of feedback produced by the freq uency correction circuit the speaker system On and place the Input ity Control located on the rear panel to the position Connect an AC VTVM to TP1 2 With a low impedance less than 100 ohms Audio Generator apply a 10 mV RMS 125 Hz signal to
12. he heat sink along with TS430 which is also part of the quiescent bias control The output from the low frequency amplifier is coupled through C535 to the woofer The signal from the woofer transducer assembly is applied to the emitter of TS436 as explained earlier in the description prominent feature of the collector circuit of this transistor is the zener diode D462 which is used to smooth the power supply voltage If an electrolytic capacitor were used the circuit would start oscillating motorboating at low frequencies The signal is coupled from the collector of TS436 to the frequency correction stage consisting of TS437 and TS438 Down to approxi mately 80 Hz the correction stage has flat frequency response Below that the signal has an increasing gain slope of Gdb octave The reason is the natural resonance of the loudspeaker which in this case is also about 80 Hz In the flat part of the response the signal is amplified by a factor of only two three while below 80 Hz the gain increases to a factor of about 20 Two transistors TS437 and TS438 were used to avoid distortion The signal at the Output of the frequency correction stage is coupled through 0542 to 692 where the feedback level may be adjusted From the wiper of R692 the signal is coupled through 0518 and R627 to the adding stage which was discussed earlier Automatic Electronic On Off Switch The arrangement for switching the sys
13. high frequency amplifier which is of similar design to the low frequency amplifier is terminated in an 8 ohm load impedance and is therefore limited to an output power of 20 watts An electronic crossover is used to divide the input signal between the two power amplifiers This crossover consists of a high pass filter feeding the high and a low pass filter feeding the low Both filters have a cutoff point of 500 Hz resulting in amplifier crossover at that frequency Since it is physically impossible for the woofer cone to produce frequencies below 25 35 Hz at a moderate sound level without resulting in high non linear distortion the response of the low frequency amplifier is rolled off below 40 Hz by high pass filter placed immediately after the low pass filter section of the electronic crossover The output of the high frequency power amplifier feeds a typical passive crossover network with a crossover point of 3500 Hz The high pass section of this crossover feeds the 1 dome type tweeter while the low pass section feeds the 2 dome mid range The output of the low frequency power amplifier feeds the 10 MFB woofer The woofer consists of a standard 10 driver with an accelerometer mounted under the dust cover at the apex of the Itis in fact this piezoelectric transducer PXE which constitutes the most important aspect of the entire system Its function is to measure the acceleration of the woofer cone
14. his circuit is similar to the 500 Hz high pass filter incorporating TS441 and likewise has a slope of 18db octave Since TS423 is in the it is coupled to the base of the next stage This stage pass filter is made up of TS424 and associated components and is again arranged in the emitter follower configuration The circuit acts as a rumble filter and all frequencies below approximately 35 Hz at 12db octave This makes the frequency response the same as that of a speaker with a natural resonance of 35 Hz The signal bandwidth limited by filters to 35 500 Hz is stage TS425 where it iscombined with the feedback signal derived from the accelerometer circuit The feedback signal arrives at the base of 79425 via C518 and 627 The normal input signal is applied via C516 and R634 The gain factor of this adding circuit is This stage is used to shape the electrical feedback signal which is taken from the load side of C535 TP 1 The low frequency amplifier operates class B Since the frequency range does not exceed 500 Hz practically no higher harmonics will be produced by the woofer and subsequently the possibility of crossover distortion is effectively suppressed without the need for class A AB operation Like the high frequency amplifier discussed earlier each output stage is comprised of a single chip Darlington device The thermistor R662 is used for thermal stability and is mounted on t
15. ience has shown that the tweeter is more vulnerable to overloads than the woofer and the mid range The signal across the tweeter is rectified by D465 and filtered by R735 and C572 Since R735 and C572 also form an RC network with a time constant of 1 second the positive voltage at the base of TS446 developes rapidly Being an emitter follower the voltage on the emitter increases along with the base The output obtained at the emitter of 5446 is coupled through the voltage divider network comprised of R737 and R761 to the base of 7440 During an overload condition the output of TS446 causes the Schmitt trigger 75439 79440 to change states thus driving TS428 into conduction With TS426 conducting the signal at RGOB is shunted to ground through TS426 and C508 and output power is reduced to near zero This reduction in loudness is an indication for the listen that the Volume control should be turned slightly counter clockwise From this moment C572 will discharge via 15446 until the emitter voltage reaches such a low value that the Schmitt trigger TS439 TS440 changes states again shutting off TS426 The music signal then passes on without attenuation Power Supply that this voltage increases slowly to the correct level as is The power supply circuits are conventional Only the necessary to prevent switching transients This is a point supply voltage for the preamplifiers source 7 is electroni to which great car
16. lated degree of flexure due to the cone s acceleration The leads to the chip are fastened to the PC board by two carefully weighed drops of solder most important consideration if assembly mass is to be accurately controlled As piezoelectric transducers generators are capacitive voltage sources they must be loaded with a high impedance to obtain a linear frequency response from them However high impedance circuits running long distances such as from the motional feedback transducer back into the power amplifier are quite susceptible to noise Therefore a junction FET has been used in the assembly as an impedance converter It will be noticed that the circuit configuration is rather unusual in that the FET drain feeds the emitter of 75436 instead of the base There are two to this approach First the FET source provides a relatively low source impedance to reduce susceptibility to noise Second the common base operation of TS436 makes the driving signal varying resistance rather than varying voltage In other words the base voltage of TS436 is fixed by the voltage divider network made up of R677 R680 R678 R679 and zener diode D462 and the conduction of TS436 is controlled by varying the value of its emitter resistor the FET This dynamic resistance drive signal makes the circuit quite insensitive to any noise signal voltage which might appear on the signal lead as the gain f
17. r 6444 puri Er 4425540112 Bushing T8432 MISCELLANEOUS pope 4nze060837 Brin Plog Stor Wooten 222980977 2128030092 Sos 1 Ecl v Tweeter ROOT BOTS 3924070092 Jack 2129120092 Viton Amir Siow Glow peru 2928790295 BAe Sion Blow 1 2189790025 5 amb Slow 025900018 DESCRIPTION ILLUSTRATION PART NO Stereo Cable 32120344 Adapter Cable 4132120331 Figure 12 Cable Chart 4 nd
18. requency Amplifier At the high frequency amplifier input there is an active high pass filter As is normally the case this filter is partially contained in the emitter to base feedback loop around the first transistor 15441 The slope of the filter is 18db octave and its 3db point is 500 Hz The amplifier itself is of a common design Its operation is class A AB to eliminate crossover distortion at low signal levels Up to about 1W of output power the ampli operates in a class A configuration and changes to class AB at higher input signal levels Each output stage is comprised of a single chip Darlington device assuring that the two transistors involved are completely complementary To insure thermal stability of the Darlington pair a negative temperature coefficient resistor thermistor R719 is used in the bias control Circuit and is mounted the Darlington package heat sink along with TS442 which is also part of the quiescent bias control The LC networks 566 5492 and 568 5493 respectively form high pass and low pass filters for the tweeter and mid range speakers Together they form a conventional Passive crossover network The series RC network across the mid range is for impedance correction at high freq vencies Coil 491 is a normal high frequency neutralizing choke Low Frequency Amplifier At the input of the low frequency channel is a low pass filter 75423 T
19. rom a voltage input at the emitter is very low It will be further noticed that ES the collector voltage of TS436 is Zener stablized This is to Place the quiescent operating point on the center of the transistors curve as the static conduction of TS436 regulates the source to drain bias on the FET which must be carefully held below a maximum value to preserve the gates high input impedance Amplifier System Input At the signal input to the Motional Feedback System are four phono jacks These are connected in two individual pairs left input and output and right input and output to allow the interconnection of two or more Motional Feed back Systems while carrying both stereo channel signals through the interconnection wiring These jack pairs feed the input channel selector switch SK B which allows the user to choose whether the particular Motional Feedback System is driven by the left or right channel signal Following the input channel selector switch the signal is attenuated to the proper level by the input Sensitivity Control R416 and applied to an emitter follower stage TS421 signal then passes through a frequency selective network which allows the frequencies over 7 KHz to be rolled off by the High Frequency Roll Off Control 417 After passing through another emitter follower TS422 the signal is applied to the active crossover filters which determine the input to the power amplifiers High F
20. tem On and Off has special feature The circuit consisting of TS447 through TS452 senses when a signal is applied to the speaker system and applies power to the high and low frequency amplifiers This feature is operative only when both the Power and Automatic switches are in the On position With the Automatic switch in the Off position the Power switch must be used to turn the system On and Off The input signal is applied to the gate of TS447 The output of this stage is coupled via C578 and R743 to the stage comprised of TS448 and TS449 where it is amplified and rectified When the input signal exceeds a preset level the Schmitt trigger TS450 and TS451 changes states and turns on the Relay Driver TS452 which in turn energizes the relay RE402 A time delay circuit located immediately ahead of the Schmitt trigger will keep the relay from de energizing during short no signal periods such as at the end of a record or tape If no signal is applied to the unit within approximately 2 minutes the Schmitt trigger will change states and the relay will de energize With the relay deeenergized only sources 6 7 and 8 have power applied to them The Power switch must be placed in the OH position to remove power from the entire unit Overload Circuit The treble speaker tweeter is protected against overload conditions which might occur when the speaker must produce maximum output for a long period of time Exper
21. ut transistors in both the low and high frequency amplifiers should be replaced with matched pairs as indicated in the Electrical Replacement Parts List After replacing the low frequency amplifier output transistors the Low Frequency Amp Quiescent Current Adjustment must be performed Likewise if the high frequency amp lifier output transistors are replaced the High Frequency Amp Quiescent Current Adjustment must be performed Misadjustment of the output transistors may cause cross over distortion and possible premature failure of the output transistors ELECTRICAL REPLACEMENT PARTS LIST r REF DESCRIPTION PART NO REF DESCRIPTION PART NO COILS TRANSFORMERS 4H1 1130029 Eur 4911030007 E Power Transformer amassooso 4911130008 nia 4111130013 3491 Son 2604 4416750715 5 3492 1919750909 Saos 38 mH 4415750809 5727 Cervon Fumi onm on 1w 1725 Carbon Pimi ohm 5 1W CAPACITORS Fio Wire Wound 12 hm 104 R738 44111042187 Electrolytic 220 mta 1112620472 A762 Eleowolye V Electrolyte 47 CONTROLS SWITCHES 47 mid 40v 45112420487 Electrolytic 47 mia 3912420861 Input Sensitivity 200K 44110120079 1912420468 High Frequency Roll O11 20K 1130317 1912420484 Gurrent Adjust Low Frog Ampl
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