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Series III 

 

Power Amplifiers

 

 

  TECHNICAL SERVI CE MANUAL 

 
 

 
 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

 

 

 

 

3800 

R E V .   B  

*TD-300001-AX* 

 

3500 

 

3350 

 

3200 

Содержание 3200

Страница 1: ...Series III Power Amplifiers TECHNICAL SERVICE MANUAL 3800 R E V B TD 300001 AX 3500 3350 3200 ...

Страница 2: ... Power Amplifiers QSC Audio Products Inc Technical Services Group Toll Free 800 772 2834 Local 714 957 7150 Fax 714 754 6173 QSC Audio Products Inc 1675 MacArthur Blvd Costa Mesa CA 92626 www qscaudio com tech_support qscaudio com ...

Страница 3: ...3 SERIES THREE POWER AMPLIFIERS ...

Страница 4: ...k Diagram 18 Detailed Explanations 18 Troubleshooting Chart 23 Introduction 23 1 Current Draw Section 23 2 Protection Circuit Problems 24 3 Faults With Signal Present 25 Series Three Test Procedures 29 Model 3200 29 Model 3350 31 Model 3500 33 Model 3800 35 Series Three Schematics 37 Model3200 37 Model 3350 38 Model 3500 Early Version 39 Model 3500 Late Version 40 Model 3800 41 Series Three PCB Dr...

Страница 5: ...wired in parallel 2 terminal barrier strip and 5 way binding post outputs wired in parallel octal input sockets provided for input transformers or active accessories ground lift terminal block Cooling Passive cooling combined with high efficiency output stage for reduced operating temperatures Unique circuit configuration allows direct metal mounting of output devices for reduced thermal stress fr...

Страница 6: ...parallel 2 terminal barrier strip and 5 way binding post outputs wired in parallel octal input sockets provided for input transformers or active accessories ground lift terminal block Cooling Passive cooling combined with high efficiency output stage for reduced operating temperatures Unique circuit configuration allows direct metal mounting of output devices for reduced thermal stress from short ...

Страница 7: ...puts wired in parallel 2 terminal barrier strip and 5 way binding post outputs wired in parallel octal input sockets provided for input transformers or active accessories ground lift terminal block Cooling Passive cooling combined with high efficiency output stage for reduced operating temperatures Unique circuit configuration allows direct metal mounting of output devices for reduced thermal stre...

Страница 8: ...6 dB signal level indicators flashing over temp indicators Cooling Passive cooling combined with high efficiency output stage for 50 reduction in dissipated heat Unique circuit configuration provides direct metal mounting of output devices to minimize short term thermal excursions of power transistors Fan assisted cooling recommended for high duty cycles at 2 ohms Amplifier Protection Indefinite s...

Страница 9: ...0 BP 001UF 100V 10 MYLAR C1 C9 D9 D18 C10 C15 QD 004410 TX BJTN 80V 25A 1 5W 2N4410 Q9 Q13 CA 222100 BP 0022UF 100V 10 MYLAR C3 Q14 CA 347050 BP 047UF 50V 10 MYLAR C7 C8 QD 004744 ZA ZENER 15V 1W 5 1N4744A Z21 Z22 CA 410100 BP 1UF 100V 10 MYLAR C5 QD 004934 DX DIODE100V 1A 200NS VP 1N493 D1 D2 CA 422100 CP 22UF 100V 5 MYLAR C4 D3 D5 CA 610035 BE 10UF 35V ELEC RADIAL E7 D6 D10 CA 647010 BN 47UF 10V...

Страница 10: ...5 BC 5 1K 1 4W 5 CF R6 RE 210001 BM RESISTOR MF 10 OK 1 1 4 R1 R2 R3 R4 RE 212101 CM 12 1K 1 2W 1 MF R7 RE 210005 BC 10K OHM 1 4W CARBON 5 R45 RE 230005 BC 30K 1 4W 5 CF R46 RE 242201 BM RESISTOR 42 2K 1 4W MET FM 1 R9 RE 239005 BC 39K 1 4W CARBON 5 R20 RE 310005 BC 100K 1 4W 5 CF R48 RE 315005 BC 150K 1 4W 5 CF R17 RE 333005 BC 330K 1 4W 5 CF R18 R19 ...

Страница 11: ...IDGE RECT QD 0003 9 ZT ZENER 3 9V 25W DZ84073ID Z15 PL 003 65 TW TIE WRAP 4 BLACK SMALL QD 0004 7 ZT ZENER 4 7V 25W DZ840731E Z16 PL 000011 TW TIE WRAP 11 WHITE LONG QD 0007 5 ZT ZENER 7 5V 25W DZ840731F Z17 PL 090751 RV RIVET FASTEX ON HEAT SINK QD 000424 TX 2SD424 NPN TO 3 TO 204AA Q12 Q13 PT 350000 AT 50K DET GAIN POT Q15 Q16 QD 250400 BX 25A 400V BRIDGE RECTIFIER B3 B4 QD 000554 TX 2SB554 PNP ...

Страница 12: ...5 CF R11 R20 R21 R61 RE 010005 CC 100 1 2W 5 CF R32 RE 033201 BM 332 1 4W 1 MF R8 RE 033005 HW 330 OHM 5 WATT WW 10 R52 RE 015005 BC 150 1 4W 5 CF R57 R58 RE 110005 BC 1K 1 4W 5 CF R5 RE 110005 EM 1K 2W 5 MOFP R47 RE 115005 BC 1 5K 1 4 W 5 CF R13 R23 R24 RE 120005 EM 2K 2W 5 MOFP R48 RE 127005 HW 2 7K 5W 5 WW R33 R34 RE 151005 BC 5 1K 1 4W 5 CF R6 RE 147005 CC 4 7K 1 2W CARBON 5 RES R12 RE 168005 ...

Страница 13: ...SULATOR D21 D22 LB 100003 SR ON SUBPANEL PL 903125 SP SPACER ROUND NYLON 0 047 L1 L2 LB 376002 MP ON SUBPANEL R14 MS 350410 HS HEAT SINK PL 905385 SP SPACER RND NYL 6 0 385 L B LD1 LD2 MS 350472 SP SUBPANEL LD3 LD4 SC 062120 PP 6 X 3 4 B P P ZINC 25A BRIDGE RECT LD5 PL 003 65 TW TIE WRAP 4 BLACK SMALL PL 909235 SP HOLDER LED 90 DEGREES NY LD1 LD2 PL 000011 TW TIE WRAP 11 WHITE LONG LD3 LD4 PL 0907...

Страница 14: ...E 000050 NR NTC THERMISTOR 50 OHM R14 RE 001005 EM 10 2W 5 MOFP R56 RE 002205 DM 22 1W 5 MOFP R15 R16 R17 R18 RE 010005 BC 100 1 4W 5 CF R11 R20 R21 R61 RE 018005 CC 180 1 2W 5 CF R32 RE 033201 BM 332 1 4W 1 MF R8 RE 045005 HW 450 OHM 5 W WIREWOUND 10 R52 RE 015005 BC 150 1 4W 5 CF R57 R58 RE 082005 BC 820 1 4W 5 CF R19 R22 RE 110005 BC 1K 1 4W 5 CF R5 RE 113005 EM 1 3K 2W 5 MOFP R47 RE 115005 BC ...

Страница 15: ...6 NW 060410 ST A 4 SPRING TOOTH LOCKWASHER P NW 060400 HN 6 32 BY 1 4 HEX NUT P D5 D6 PC 000046 AM MAIN NPN BOARD PL 000220 MI D5 D6 PL 905100 SP SPACER ROUND NYLON 6 0 L1 L2 PT 250000 AT RES VAR IT 5K 20 0 15W CARB TR1 QD 0004 7 ZT ZENER 4 7V 25W DZ840731E Z1 QD 000424 TX 2SD424 NPN TO 3 TO 204AA Q3 Q4 Q5 Q6 Q7 Q8 Q9 Q10 Q11 Q12 QD 001847 TH SJ1847 PNP TO 66 TO 213AA Q1 Q2 QD 004934 DX DIODE100V ...

Страница 16: ...DM 6 8 OHM 1W MET OXIDE 5 R13 NW 060410 ST LCKWSHR ON HEAT XFER BRKT MTG PEMS RE 247005 BC 47K 1 4 W 5 CF R11 NW 060400 HN 6 32 BY 1 4 HEX NUT PEMS RE 210005 BC 10K OHM 1 4W CARBON 5 R2 R12 PC 000047 BM MAIN PCB BOARD RE 230005 BC 30K 1 4W 5 CF R3 PL 000220 MI MICA WSHR D8 D9 RE 310005 BC 100K 1 4W 5 CF R8 R10 PL 903125 SP SPACER ROUND NYLON 0 047 R22 RE 333005 BC 330K 1 4W 5 CF R6 R7 PT 250000 AT...

Страница 17: ...8 BG GAIN PCB BOARD PL 905385 SP SPACER RND NYL 6 0 385 L B LD1 LD2 LD3 LD4 LD5 PL 909235 SP HOLDER LED 90 DEGREES NY LD1 LD2 LD3 LD4 LD5 QD 000134 LR LED RED T 1 3 4 LD1 LD2 QD 000134 LX LED R G T 1 3 4 LD5 QD 000134 LY LED YEL T 1 3 4 LD3 LD4 QD 0003 9 ZT ZENER 3 9V 25W DZ84073ID Z3 QD 004744 ZA DIODE 15V 1W 5 1N4744A Z1 Z2 QD 004934 DX DIODE100V 1A 200NS VP 1N493 D1 D2 D3 D4 QD 1 5200 BX DIODE ...

Страница 18: ...he power supplies are DC coupled with the usual transformer center tap We use a speaker relay for DC protection as discussed in section 6 The second unusual feature is that we reverse the usual location of the speaker and ground terminals For reasons explained in sections 4 and 5 we ground the common collectors of the output transistors and take the audio output from the midpoint of the power supp...

Страница 19: ...termined by the base current to each driver through 1K resistors and 3 9V zener diodes R19 and R22 Z15 and Z16 When the op amp rails are at their normal 15V this current is about 9ma and results in about a 25A current from the output transistors This is sufficient to deliver 625 watts RMS to a two ohm load The output transistors can withstand this much current into a short for a few seconds but wo...

Страница 20: ...han at full output By having a lower level DC supply for lower levels of output voltages up to 50 we greatly reduce waste voltage and power for lower level signals Of course the big problem is to switch over smoothly between high an low power stages To assist this especially at high frequencies we have a speed up network R23 and C17 which makes Q3 switch sooner at very high frequencies and coil L1...

Страница 21: ...t 2V This is enough to forward bias the bridge rectifier B2 and turn on Q19 Note that Q19 is connected to the rectifier so that either polarity of DC will trigger it When Q19 turns on it discharges E7 and shuts off the relay The recharge time of E7 prevents destructive chattering of the relay Important Note that the entire relay circuit is referenced to the power supply not to ground Therefore be ...

Страница 22: ...22 ...

Страница 23: ...or pins a hard short solder short will read virtually zero volts A reading of 0 6 1V above ground indicates a reversed diode or shorted output A reading of 1 2 volts could mean a bad driver but outputs may be good Check for shorted mounting of the switching diodes D21 and D22 by measuring voltages of both pins A pin with zero voltage usually the pin connected to the flange may be shorted to ground...

Страница 24: ... is enough to activate zener diode Z17 which turns off the base of Q18 which is at 2 2V when on and shuts off the relay circuit The latching effect holds the circuit off until the PTC voltage has cooled off and fallen by several volts DC PROTECTION Output voltage is sensed through R27 but all frequencies above about 10Hz are filtered by nonpolar E6 Excess voltage at subaudio frequencies will charg...

Страница 25: ...s too small of a resistance a low voltage on E7 turns Q18 on too soon d Missing or too large of a resistance at R30 no off current 3 Possible causes of an excess muting delay a Check the voltage across the timing capacitor E7 If it rises normally but the circuit is slow to turn on check Z17 lift temporarily LD6 whether bad or intermittent and whether R30 is too low b If the timing capacitor voltag...

Страница 26: ... the current is too low into a shorted output as well as a 2 ohm load check a If the IC rails are o k some possible causes are i Bias resistor R19 or R22 measures too high ii Very low gain resistors see below 4 If the current is too low into a short only and is normal into typical loads a Check whether the clip LED LD2 is shorted 1 5A rectifier B1 is shorted or R11 is too low b Check whether the 3...

Страница 27: ...can indicate a problem in minor stability components see that section above b Also check the output filter R56 L2 R49 R50 C5 and inner coil R55 and L1 c Alternatively the crossover or step may be larger than usual and need work see below 3 Crossover distortion a Possible causes of severe crossover distortion i Shorted bias diode D5 or D6 ii Open circuit trace from lower voltage driver to lower out...

Страница 28: ...is bad d Possible causes of high frequency distortion i The value of C3 is too high x10 for the slew rate compensation capacitor ii The base resistors R15 R16 R17 or R18 on the output devices are missing in this case the amp usually draws excessive AC current near clipping 20kHz no load iii Step distortion see above Wrong Gain 1 Possible causes of gain that is too high a One of the two feedback re...

Страница 29: ... visible on the positive and negative halves of the waveform still into no load on channel B of the oscilloscope d Switch the load to 8 ohms and vary the amplifier gain just above and below the step switching level Watch for obvious step oscillation This test must be done when the amplifier channel is cold since any tendency to instability will disappear as the amplifier warms up You may experienc...

Страница 30: ...x2 output and observe power output at 20Hz 0 5dB max and 20kHz 0 5dB max 10 Temperature cycle a Switch to the 2 6 ohm load Increase the signal to the point of clipping and short the output of the amplifier The clip LED should be on Check for recovery into 2 6 ohms cold b Check the IC rails 5 to 7VDC 1VDC c After 1 to 3 minutes the Temp LED should start flashing and 2 to 3 minutes later the signal ...

Страница 31: ...visible on the positive and negative halves of the waveform still into no load on channel B of the oscilloscope d Switch the load to 8 ohms and vary the amplifier gain just above and below the step switching level Watch for obvious step oscillation This test must be done when the amplifier channel is cold since any tendency to instability will disappear as the amplifier warms up You may experience...

Страница 32: ... or 9 5dB output and observe power output at 20Hz 0 5dB max and 20kHz 0 5dB max 10 Temperature cycle a Switch to the 2 ohm load Increase the signal to the point of clipping and short the output of the amplifier The clip LED should be on Check for recovery into 2 ohms cold b Check the IC rails 5 to 7VDC 1VDC c After 1 to 3 minutes the Temp LED should start flashing and 2 to 3 minutes later the sign...

Страница 33: ...isible on the positive and negative halves of the waveform still into no load on channel B of the oscilloscope d Move the wiring harness and tap the circuit boards with a non conductive implement such as the handle of a small screwdriver and watch the scope output and distortion trace for intermittency Remove the 8 ohm load 4 DC protect a Check that there is no load on the output of the amplifier ...

Страница 34: ...er Select a 2kHz signal input to the amplifier b Adjust the amp gain to obtain 215 watts x2 or 7 5dB output and observe power output at 20Hz 0 5dB max and 20kHz 0 5dB max 10 Temperature cycle a Switch to the 2 ohm load Increase the signal to the point of clipping and short the output of the amplifier The clip LED should be on Check for recovery into 2 ohms cold b Check the IC rails 5 to 7VDC 1VDC ...

Страница 35: ...aveform still into no load on channel B of the oscilloscope d Switch the load to 8 ohms and vary the amplifier gain just above and below the step switching level Watch for obvious step oscillation This test must be done when the amplifier channel is cold since any tendency to instability will disappear as the amplifier warms up You may experience a severe glitch on the negative step which can be c...

Страница 36: ...00W x 2 10 Temperature cycle a Switch to the 2 ohm load Increase the signal to the point of clipping and short the output of the amplifier The clip LED should be on Check for recovery into 2 ohms cold b Check the IC rails 5 to 7VDC 1VDC c After 1 to 3 minutes the Temp LED should start flashing and 2 to 3 minutes later the signal mute relay should go off and the power protect LED should turn red Ch...

Страница 37: ...Series Three Schematics Model3200 ...

Страница 38: ...Model 3350 ...

Страница 39: ...Model 3500 Early Version ...

Страница 40: ...Model 3500 Late Version ...

Страница 41: ...Model 3800 ...

Страница 42: ...Series Three PCB Drawings Model 3200 PCB ...

Страница 43: ...Model 3350 PCB ...

Страница 44: ...Model 3800 46A PCB ...

Страница 45: ...Model 3800 47A PCB ...

Страница 46: ...Model 3800 48B PCB ...

Страница 47: ...Model 3800 Gain PCB ...

Страница 48: ...QSC Audio Products Inc 1675 Mac Arthur Blvd Costa Mesa CA 92626 Tel 714 754 6175 Fax 714 754 6173 ...

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