McCulloch MC312 Service Manual
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McCulloch MC312 Service Manual

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MC312
POWER AMPLIFIER
SERIAL NO. AGW1001 And Above
SERVICE MANUAL
CONTENTS
Performance Specifications ........................................................ 2
Notes ......................................................................................... 2
Rear Panel ................................................................................. 2
Section Location ........................................................................ 3
Block Diagram ........................................................................... 4
Interconnect Diagram and Parts List ...................................... 5 - 6
Main Schematic, PCB and Parts List .................................... 7 - 11
Rectifier Schematic, PCB and Parts List ....................................12
Capacitor, PCB and Parts List .............................................13 - 14
Left Input, Schematics, PCB and Parts List ..........................15 - 16
Right Input, Schematic, PCB and Parts List ......................... 17 - 18
Heatsink Schematic, PCB and Parts List .............................19 - 22
Left Terminal Schematic, PCB and Parts List ......................23 - 24
Display/Left Meter/Right Meter Light ..................................27 -28
Repacking Instruction .............................................................. 29

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  • Page 1: Table Of Contents

    MC312 POWER AMPLIFIER SERIAL NO. AGW1001 And Above SERVICE MANUAL CONTENTS Performance Specifications ............2 Notes ..................2 Rear Panel ................. 2 Section Location ................ 3 Block Diagram ................4 Interconnect Diagram and Parts List ........5 - 6 Main Schematic, PCB and Parts List ........7 - 11 Rectifier Schematic, PCB and Parts List ........12...

  • Page 2: Performance Specifications

    McINTOSH LABORATORY, INC., BINGHAMTON, NY HANDCRAFTED IN USA WITH US AND IMPORTED PARTS Standby: less than 0.5 watt 3.4 Volts Balanced Note: Refer to the rear panel of the MC312 for the correct 1.7 Volts Unbalanced voltage. Signal To Noise Ratio (A-Weighted)

  • Page 3: Section Location

    MC312 SECTION LOCATIONS Top View Bottom View R-METER L-METER LIGHT LIGHT DISPLAY MAIN RECTIFIER CAPACITOR HEATSINK RIGHT TERMINAL LEFT TERMINAL RIGHT INPUT LEFT INPUT...

  • Page 4: Block Diagram

    MC312 BLOCK DIAGRAM POSITIVE CURRENT LIMITER VOLTAGE RECTIFIER METER DIFF POWER VOLTAGE LEFT PREDRIVER INDICATOR GUARD DRIVER OUTPUT OUTPUT METER HOLD 8 ohm SWITCH OUTPUT 4 ohm CURRENT ThermalTrak AUTO- SOURCE DC BIAS FORMER 2 ohm DIFF VOLTAGE PREDRIVER DRIVER...

  • Page 5: Interconnect Diagram And Parts List

    MC312 INTERCONNECT MC312 TRANSFORMER WIRING AND FUSE REPLACEMENT (CONTACT MCINTOSH FOR CORRECT TRANSFORMER P/N) Voltage BLK BLK/GRY GRY VIO WHT/VIO BRN 1 BRN 2 Jumper Location (JMP1) Main Fuse (F1) T12AH250V T10AH250V T10AH250V T5AH250V T5AH250V TERMINAL T5AH250V HEATSINK CA14 CA16...
  • Page 6 MC312 INTERCONNECT PARTS LIST Ref. No. Description Part No. Ref. No. Description Part No. MCINTOSH BINDING POST 084226 MCINTOSH BINDING POST 084226 CA14 CABLE ASSY TERMINAL/HEATSINK 173339 MCINTOSH BINDING POST 084226 CA15 CABLE ASSY TERMINAL/HEATSINK 173339 MCINTOSH BINDING POST 084226...

  • Page 7: Main Schematic, Pcb And Parts List

    MC312 MAIN 752407 SCH 1 of 3 CURRENT LOG AMP +14VML Main - Meter U24:1 1000pF -5VML -5VML 33.2k METER DRIVER 1000µF +14VML +14VML U24:2 18.2k HS OUT L J9:1 U26:2 AUTOF L J9:2 VOLTAGE LOG AMP PGND +15V +14VML...
  • Page 8 MC312 MAIN 752407 SCH 2 of 3 173085 +12V J11:1 J11:4 350mA ON/OFF 100V JMP1 110V J11:7 120V 47.5k PRIMARY J11:10 J12:10 J12:1 220V 230V 240V J12:4 AC DET PGND +12V J13:2 TEST ONLY AC DETECTOR NO CONNECTION APPLY 12VDC...
  • Page 9 MC312 MAIN 752407 SCH 3 of 3 METER V PG LIGHT L MET V J5:6 DRIVERS MUTE J3:1 MUTE PGND J5:5 L PG J3:2 L PG J5:1 +15V J3:3 +15V PANEL LIGHT L PG J5:3 L PG LT J3:4 -15V...
  • Page 10 MC312 MAIN 752407 PCB MAIN 752407 PARTS LIST Ref. No. Description Part No. Ref. No. Description Part No. Ref. No. Description Part No. Ref. No. Description Part No. CAP X7R .1uF 20% 50V SMD0805 061365 CAP X7R .47uF 20% 50V SMD0805...
  • Page 11 MC312 MAIN 752407 PARTS LIST (Cont’d.) Ref. No. Description Part No. Ref. No. Description Part No. Ref. No. Description Part No. Ref. No. Description Part No. TRANSISTOR NPN A05 SMD 132333 RES 2.21M 1% 1/8W SMD0805 145043 RES 332K 1% 1/8W SMD0805 145039 THERMISTOR 2.5 15A...

  • Page 12: Rectifier Schematic, Pcb And Parts List

    MC312 RECTIFIER 752098 SCH and PCB +V BRG -V BRG BRIDGE RECTIFIER RECTIFIER 752098 PARTS LIST Ref. No. Description Part No. CAP POLYPROP 0.22UF 400V 20% 064438 RECTIFIER BRIDGE PCB 35A 600V 070187 BLADE FASTON W/FEET 117708 BLADE FASTON W/FEET...

  • Page 13: Capacitor, Pcb And Parts List

    MC312 CAPACITOR 752097 SCH J5:1 J6:1 +V AMP +V AMP J6:2 J5:2 -V AMP -V AMP PGND...
  • Page 14 MC312 CAPACITOR CAPACITOR 752097 PCB 752097 PARTS LIST Ref. No. Description Part No. CAP ELECT 27000UF 100V 066596 CAP ELECT 27000UF 100V 066596 CAP ELECT 27000UF 100V 066596 CAP ELECT 27000UF 100V 066596 BLADE FASTON W/FEET 117708 BLADE FASTON W/FEET...

  • Page 15: Left Input, Schematics, Pcb And Parts List

    MC312 LEFT INPUT 752175 SCH 1.58k 22.1 2.00k 2.21k 2.21k +14V +14V U1:1 10µF J3:1 2.21M L PG PG AT T L PG -14V J5:5 Vocm GN D J5:3 -14V L IN P L IN P U3:2 J5:4 1.58k 22.1 2.00k...
  • Page 16 MC312 LEFT INPUT LEFT INPUT 752175 PCB 752175 PARTS LIST Ref. No. Description Part No. CAP ELECT 10UF 50V SMD 066602 CAP ELECT 10UF 50V SMD 066602 CAP NPO 100pF 5% 200V SMD0805 061390 CAP NPO 100pF 5% 200V SMD0805...

  • Page 17: Right Input, Schematic, Pcb And Parts List

    MC312 RIGHT INPUT 752176 SCH 1.58k 22.1 2.0k 2.21k 2.21k +14V +14V U1:1 10µF J3 :2 2.21M R PG PG ATT R PG J5 :5 -14V Vocm GN D J5 :3 -14V R INP R IN P U3:2 J5 :4 1.58k...
  • Page 18 MC312 RIGHT INPUT RIGHT INPUT 752176 PCB 752176 PARTS LIST Ref. No. Description Part No. CAP ELECT 10UF 50V SMD 066602 CAP ELECT 10UF 50V SMD 066602 CAP NPO 100pF 5% 200V SMD0805 061390 CAP NPO 100pF 5% 200V SMD0805...

  • Page 19: Heatsink Schematic, Pcb And Parts List

    MC312 HEATSINK 752182 SCH 1 of 2 +V AMP DIFFERENTIAL VOLT AGE 47µF J1:4 PG AT T J1:5 PG AT T FB COM J1:1 2.21M FB COM DRV + 1.8V GN D J1:3 -18V 2.21M AMP MUTING 22.1k CURREN T...
  • Page 20 MC312 HEATSINK 752182 SCH 2 of 2 +V AM P 1. 8V DRV + D R IVER 1. 2V Q29:1 C U R R EN T OU TPU TS LI M ITER Q31:1 1.8k Q33:1 - BIAS ADJUSTMENT - Q35:1...
  • Page 21 MC312 HEATSINK HEATSINK 752182 PCB 752182 PARTS LIST Ref. No. Description Part No. Ref. No. Description Part No. CAP ELECT 10UF 50V 066445 BLADE FASTON W/FEET 117708 CAP ELECT 10UF 50V 066445 CONN 2 PIN MALE 117213 CAP X7R .1uF 20% 50V SMD0805...
  • Page 22 MC312 HEATSINK 752182 PARTS LIST (Cont’d.) Ref. No. Description Part No. Ref. No. Description Part No. Ref. No. Description Part No. Ref. No. Description Part No. RES FP 1.1 OHM 1/4W 5% 137002 RES MO 47 OHM .5W 5% 137102 RES MO 1.8k .5W 5%...

  • Page 23: Left Terminal Schematic, Pcb And Parts List

    MC312 LEFT TERMINAL 752179 SCH LEFT OUTPUTS L (+) L FB8 FB 8 J6:2 J6:3 L (+) L FB2 FB 2 J6:1...
  • Page 24 MC312 LEFT TERMINAL 752179 PCB LEFT TERMINAL 752179 PARTS LIST Ref. No. Description Part No. CAP POLYPROP 0.15UF 10% 275VDC 064464 CAP POLYPROP 0.047UF 10% 275VDC 064466 BLADE FASTON W/FEET 117708 BLADE FASTON W/FEET 117708 BLADE FASTON W/FEET 117708 BLADE FASTON W/FEET...

  • Page 25: Right Terminal Schematic, Pcb And Parts List

    MC312 RIGHT TERMINAL 752180 SCH RIGHT OUTPUTS R (+) R FB8 FB 8 J6:2 J6:3 R (+) R FB2 FB 2 J6:1...
  • Page 26 MC312 RIGHT TERMINAL 752180 PCB RIGHT TERMINAL 752180 PARTS LIST Ref. No. Description Part No. CAP POLYPROP 0.15UF 10% 275VDC 064464 CAP POLYPROP 0.047UF 10% 275VDC 064466 BLADE FASTON W/FEET 117708 BLADE FASTON W/FEET 117708 BLADE FASTON W/FEET 117708 BLADE FASTON W/FEET...

  • Page 27: Display/Left Meter/Right Meter Light

    MC312 DISPLAY/ L METER LIGHT/ R METER LIGHT 752169 SCH R METER LIGHT L CAL 2 J1:1 L MET J1:2 HOLD J1:3 J7:9 J10:4 L CAL 1 J7:8 J10:5 J1:4 J7:7 +15V J10:6 +15VR +15V L PG LT J1:5 R PG LT...
  • Page 28 MC312 DISPLAY/ L METER LIGHT/ R METER LIGHT 752169 SCH DISPLAY L METER LIGHT R METER LIGHT 752169 PARTS LIST Ref. No. Description Part No. Ref. No. Description Part No. Ref. No. Description Part No. Ref. No. Description Part No.

  • Page 29: Repacking Instruction

    MC312 REPACKING INSTRUCTIONS In the event it is necessary to repack the equipment for shipment, the equipment must be packed exactly as shown below. It is very important that the four plastic feet are attached to the bottom of the equipment. Four 1/4 - 20x2-1/4 inch screws and washers must be used to fasten the unit securely to the bottom pad and wood skid.
  • Page 30 MC312 POWER AMPLIFIER SERIAL NO. AGW1001 And Above 8Ω 4Ω 2Ω 2Ω 4Ω 8Ω 120V 50/60Hz T 10AH 250V 6.6 AMPS RIGHT OUTPUT LEFT OUTPUT CLASS 2 WIRING CLASS 2 WIRING CAUTION SERIAL RISK OF ELECTRIC SHOCK M C 3 1 2 P O W E R A M P L I F I E R...

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