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Performance Specifications ..........................................2
Notes ...........................................................................2
Rear Panel ...................................................................3
Section Location ..........................................................4
Block Diagram .......................................................5 - 6
Interconnection Diagram ........................................7 - 8
Main Schematic and PCB .....................................9 - 16
Rectifier Schematic and PCB ..............................17 - 20
Capacitor Schematic and PCB ............................21 - 24
SERVICE MANUAL
MC302
POWER AMPLIFIER
SERIAL NO. AAV1083 And Above
CONTENTS
Left Input Schematic and PCB .............................25 - 28
Right Input Schematic and PCB ..........................29 - 32
Heatsink Schematic and PCB ..............................33 - 38
Left Terminal Schematic and PCB .......................39 - 42
Right Terminal Schematic and PCB .....................43 - 46
Display Schematic and PCB................................47 - 50
Parts List .............................................................53 - 58
Repacking Instruction ................................................59
MC302

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Summary of Contents for McIntosh MC302

  • Page 1: Table Of Contents

    MC302 MC302 POWER AMPLIFIER SERIAL NO. AAV1083 And Above CONTENTS Performance Specifications ..........2 Left Input Schematic and PCB ......25 - 28 Notes ................2 Right Input Schematic and PCB ......29 - 32 Rear Panel ..............3 Heatsink Schematic and PCB ......33 - 38 Section Location ............4...
  • Page 2: Performance Specifications

    240V ~ 50/60Hz at 3.3 Amps +0, -3.0dB from 10Hz to 100,000Hz Standby: less than 0.5 watt Note: Refer to the rear panel of the MC302 for the correct voltage. Input Sensitivity (for rated output) 3.4 Volts Balanced Overall Dimensions 1.7 Volts Unbalanced...
  • Page 3: Rear Panel

    MC302 REAR PANEL...
  • Page 4: Section Location

    SECTION LOCATION...
  • Page 5: Block Diagram

    MC302 BLOCK DIAGRAM POSITIVE CURRENT LIMITER VOLTAGE RECTIFIER METER POWER DIFF VOLTAGE LEFT INDICATOR PREDRIVER OUTPUT GUARD DRIVER OUTPUT METER HOLD 8 ohm SWITCH OUTPUT 4 ohm CURRENT ThermalTrak AUTO- SOURCE DC BIAS FORMER 2 ohm DIFF VOLTAGE PREDRIVER DRIVER...
  • Page 6 INTERCONNECT MC302 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 CA18 T10AH250V WHT 18 AWG T10AH250V T5AH250V T5AH250V TERMINAL T5AH250V...
  • Page 7 MC302 MAIN 751291 SCH 1 OF 3 J1:1 J1:4 PRIMARY J1:7 REFER TO CONVERSION CHART FOR PROPER JUMPER LOCATION J1:10 J2:10 J2:1 J2:4 J3:2 TEST ONLY ON/OFF NO CONNECTION APPLY 12VDC TO ENERGIZE RELAYS W ITH NO AC POWER J3:1 1.2V...
  • Page 8 MAIN 751291 SCH 2 OF 3 +14VML U8:1 33.2k -5VML 1000pF L M ETER DRIVER -5VML +14VML +14VML U8:2 1000µF FUNC 1 J29:1 FUNC 2 18.2k U10:2 FUNC 1 J29:2 FUNC 2 L METER LOG AMP +15V +14VML 200k +14VML L MET V 10µF L MET...
  • Page 9 MC302 MAIN 751291 SCH 3 OF 3 +15V PC OUTPUT +15V +15V DRIVER 13.6V MODE J26:1 MODE MUTE J21:5 13.2V MUTE -18V +15V J26:5 +15V 12.6V L PG LT J21:1 -15V J26:7 -15V +15V J21:3 +15V PC OUT J26:3 PC OUTPUT...
  • Page 10 MAIN 751291 PCB 130106 Rev A...
  • Page 11 MC302 RECTIFIER 751288 SCH +V BRG BRIDGE RECTIFIER -V BRG +V AM P J1:1 +V AMP -V AM P J1:2 -V AMP +V AM P J2:1 -V AM P J2:2...
  • Page 12 RECTIFIER 751288 PCB...
  • Page 13 MC302 CAPACITOR 751290 SCH +V CAP -V CAP...
  • Page 14 CAPACITOR 751290 PCB...
  • Page 15 MC302 LEFT INPUT 751208 SCH 1.65k 22.1 2.21k 2.21k 2.21k +14V +14V U1:1 Vocm -12V J7:5 L PG L PG HT SNK PG ATT 2.21M 10µF 22.1k -14V J7:3 J2:2 J5:11 -14V J7:4 L (+) L + INP J2:4 J5:9...
  • Page 16 LEFT INPUT 751208 PCB...
  • Page 17 MC302 RIGHT INPUT 751225 SCH 1.65k 22.1 2.21k 2.21k 2.21k +14V +14V U1:1 -12V Vocm J4:5 R PG R PG HT SNK PG ATT 2.21M 10µF -14V J4:3 -14V J4:4 R (+) R + INP U3:2 1.65k 2.21k J4:1 22.1 2.21k...
  • Page 18 RIGHT INPUT 751225 PCB...
  • Page 19 MC302 HEATSINK 751293 SCH 1 OF 2 71.8V 71.6V +V AMP 47 .5 W 70.5V 69.9V 70.6V DIFFERENTIAL VOLTAGE J1:2 J1:4 69.5V 47uF -.5V -.5V PG ATT J1:5 PG ATT FB COM J1:1 FB COM DRV + -19.5V -19.5V 1.8V 2.21M...
  • Page 20 HEATSINK 751293 SCH 2 OF 2 +V AMP 1.8V DRV + DRIVER 1.2V Q28:1 CURRENT Q30:1 OUTPUTS LIMITER 1.8V Q32:1 BIAS ADJUSTMENT Q34:1 ADJUST R52 FOR 21-25 mVDC ACROSS J5 WITH NO INPUT SIGNAL Q36:1 AND HEATSINKS COOL Q38:1 J5:1 BIAS [-] 1.5k J5:2...
  • Page 21 MC302 HEATSINK 751293 PCB...
  • Page 22 LEFT TERMINAL 751210 SCH LEFT OUTPUTS J5:3 L (+) L FB8 FB 8 J5:5 J5:1 L (+) L FB2 FB 2...
  • Page 23 MC302 LEFT TERMINAL 751210 PCB...
  • Page 24 RIGHT TERMINAL 751226 SCH J5:3 R (+) R FB8 FB 8 J5:5 J5:1 R (+) R FB2 FB 2 RIGHT OUTPUTS...
  • Page 25 MC302 RIGHT TERMINAL 751226 PCB...
  • Page 26 10 11 DISPLAY/METER LIGHT METER LIGHT 751139 SCH 751139 SCH J5:1 J7:8 POWER J5:3 J7:10 J5:5 J7:12 DISPLAY FP OFF J1:7 FP OFF FP ON J1:4 FP ON J1:1 R INTENSITY R COLOR J5:2 J7:7 J5:4 J7:9 R BLU R BLU J5:6 J7:11 R GRN...
  • Page 27 MC302 10 11 DISPLAY/METER LIGHT 751139 PCB...
  • Page 28 NOTES...
  • Page 29: Parts List

    751204 DIODE SMALL SIGNAL 4148 SMD 070199 ASSY AUTOFORMER POTTED 751204 DIODE SMALL SIGNAL 4148 SMD 070199 CONTACT McINTOSH SERVICE DEPT DIODE SMALL SIGNAL 4148 SMD 070199 MAIN PCB 751291 HEADER SHROUDED 10 PIN 2MM 117973 CAP 3300PF 250V UL/CSA...
  • Page 30 PARTS LIST (Cont’d.) MAIN PCB 751291 (Cont’d.) Ref. No. Description Part No. Ref. No. Description Part No. BLADE FASTON W/FEET 117708 RES SMD0805 33.2K 1/8W 1% 145033 BLADE FASTON W/FEET 117708 RES SMD 0805 22.1K 1/8W 1% 145012 BLADE FASTON W/FEET 117708 RES SMD0805 1K 1/8W 1% 145007...
  • Page 31 MC302 PARTS LIST (Cont’d.) RECTIFIER PCB 751288 (Cont’d.) Ref. No. Description Part No. Ref. No. Description Part No. RES MF 2.21K 1% 1/4W 144584 BLADE FASTON W/FEET 117708 RES FP 10 OHM 5% 1/4W 137105 BLADE FASTON W/FEET 117708 RES FP 10 OHM 5% 1/4W...
  • Page 32 PARTS LIST (Cont’d.) HEATSINK ASSY 751293 Ref. No. Description Part No. Ref. No. Description Part No. TRANSISTOR PNP 2SA1312 SMD 132344 CAP ELECT 10UF 50V 066445 TRANSISTOR NPN A05 SMD 132333 CAP ELECT 10UF 50V 066445 TRANSISTOR NPN 2SC3324 SMD 132345 CAP MONO .1UF 50V ±20% X7R SMD 061365...
  • Page 33 MC302 PARTS LIST (Cont’d.) HEATSINK ASSY PCB 751293 (Cont’d.) Ref. No. Description Part No. Ref. No. Description Part No. TRANSISTOR NPN THERMALTRAK 132330 RES MF 2.21 OHM 1% 1/4W 144607 (Q38) HEATSINK 018698 RES MF 806 OHM 1% 1/4W 144512 (Q38) ISOSTRATE 5.700 X 1.010...
  • Page 34 PARTS LIST (Cont’d.) DISPLAY PCB 751139 (Cont’d.) Ref. No. Description Part No. Ref. No. Description Part No. RES SMD0805 221 1/8W 1% 145001 (DS2) LED SPACER .220 LENGTH 163001 RES SMD0805 221 1/8W 1% 145001 LED GREEN 5MM 30 DEG 058190 RES SMD0805 475 1/8W 1% 145020...
  • Page 35: Repacking Instruction

    If a shipping carton or any of the interior 401212 1/4 - 20x2-1/4 cap screw part(s) are needed, please call or write Customer 104058 Flat washer Service Department of McIntosh Laboratory. Refer to page 3. Please see the Part List for the correct part numbers.
  • Page 36 The continuous improvement of its products is the policy of McIntosh Laboratory Incorporated, who reserve the right to improve design without notice. Because of the constant upgrading of McIntosh products’ circuitry and components, the Company cannot insure, and does not warrant, the accuracy of the within schematic material, which is intended for information only.

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Aav1083