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MI254
4 CHANNEL
POWER AMPLIFIER
SERIAL NO . AGY1001 And Above
CONTENTS
Performance Specifications . . . . . . . . . . . . . 2
Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Rear Panel . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Section Locations . . . . . . . . . . . . . . . . . . . . 4
Interconnection Diagram . . . . . . . . . . . . . . . 5
Main Schematic and PCB . . . . . . . . . . . 6 - 13
SERVICE MANUAL
Input Schematic and PCB . . . . . . . . . . 14 - 23
Power Source Schematic and PCB . . . . 24 - 27
Display Schematic and PCB . . . . . . . . . 28 - 33
Amplifier Module PCB . . . . . . . . . . . . . . 34 - 35
Parts List . . . . . . . . . . . . . . . . . . . . . . . 36 - 47
Repacking Instructions . . . . . . . . . . . . . . . . 48
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Summary of Contents for McIntosh MI254
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Page 1: Table Of Contents
MI254 4 CHANNEL POWER AMPLIFIER SERIAL NO . AGY1001 And Above CONTENTS Performance Specifications . . . . . . . . . . . . . 2 Input Schematic and PCB . -
Page 2: Performance Specifications
– – – BUS 2 Output Load Impedance 18,000 ohms Unbalanced MI 254 4 CHANNEL POWER AMPLIFIER McINTOSH LABORA TORY, INC., BINGHAMTON, NY 8 and 4 ohms HANDCRAFTED IN USA WITH Voltage Gain SERIAL US AND IMPORTED PARTS NUMBER CHANNEL 4/L... -
Page 3: Section Locations
SECTION LOCATIONS INTERCONNECT Top View INPUT MAIN MODULE DISPLAY... - Page 4 MAIN 320656 SCH 1 of 3 U_MI254-POWER U_MI254-MCU MI254-POWER.SchDoc MI254-MCU.SchDoc STB_EN STB_EN AC_DET AC_DET nFATAL_A nFATAL_A Z3-4_DET Z3-4_DET Z1-2_DET Z1-2_DET SG_MUTE SG_MUTE BUS1_EN BUS1_EN BUS2_EN BUS2_EN BUS_DET BUS_DET Ready_1 Ready_1 EN_AMP1 EN_AMP1 Current Limiting_1 Current Limiting_1 DC_ERROR1 DC_ERROR1 Ready_2 Ready_2...
- Page 5 MAIN 320656 SCH 2 of 3 3V3S U301 D301 L301 ASM1117-3.3 IN1_N Q301 3V3S H302 Mute circuit +15VA U302 L78L12ACUTR +12V Q302 D302 DTA114 chassis2 chassis8 chassis9 R305 SS36 C3326 R306 +18V +15VA Vout 0.1R 2.2K U304 470R C302 R301 C301 LM317M C303...
- Page 6 MAIN 320656 SCH 3 of 3 CLIP INDICATE VCLP1 VCLP2 R193 R194 TO 24K; one channel 250W/8OHM D120 D122 R198 two channel 240W/8OHM 1N4148 1N4148 D121 D119 1SS355 R172 R194 R176 R197 1N4148 CLIP_CH1 CLIP_CH2 100K HV+_A1 100K HV+_A2 R173 R178 OUTH1 Q107...
- Page 7 MAIN 320656 PCB Red----- Green P305 P304 XM 304 P303 Red----- Green C383 D315 C344 XM 301 P306 P301 C411 D313 R333 R332 D316 XM 302 Q335 C343 XM 303 C410 D314 C382 Q320 C408 Q334 R403 C379 C380 R397 R418 R420 L311...
- Page 8 INPUT 320659 SCH 1 of 3 U_MI254-PRE AMP U_MI254-BUS IN MI254-PRE AMP.SchDoc MI254-BUS IN.SchDoc BUS1L+ BUS1L+ BUS1L- BUS1L- BUS2L+ BUS2L+ BUS2L- BUS2L- BUS1R+ BUS1R+ BUS1R- BUS1R- BUS2R+ BUS2R+ BUS2R- BUS2R- AIN1 AIN1 AIN2 AIN2 AIN3 AIN3 AIN4 AIN4 SG_CH1 SG_CH1...
- Page 9 INPUT 320659 SCH 2 of 3 D5001 D5002 J5001 M200 2*10 C5001 BAV21WS BAV21WS 22nJ SG_CH1 SG_CH2 +15VA -15VA SG_CH1 SG_CH2 J5002A K5001A U5001A L IN R5001 BUS1L 332R R5002 +15VA +15VA RCA4 BUS1L+ 909R BUS1L+ -15VA 11 12 -15VA C5002 HFD4/5-SR 13 14...
- Page 10 INPUT 320659 SCH 3 of 3 D1001 D1002 J1001 C1002 BAV21WS BAV21WS 100nJ C1003 C1004 +15VA -15VA 100nJ 100nJ J1002 U1003B BUS1R+ U1001B SW1001A R1007 R1008 R1009 OPA2134 C1005 SW1001B AIN1 OPA2134 BUS2R+ SG1+ THD adjust C1009 BUS1R-_a1 BUS1R+_a1 332R R1011 2K21 R1012...
- Page 11 INPUT 320659 PCB Bus L Bus R J 4003 J 3003 J 2003 J 1003 C5029 C5018 C5010 C5004 X M5001 D 5040 C2014 C2026 C 5019 R5010 C5007 R5026 C4014 C4026 X M5010 X M5012 X M5014 C5022 C4010 C4027 C3010 C3027...
- Page 12 INPUT 320659 PCB Z3 RED WHITE WHITE X M5016 X M5020 XM 5005 X M5018 XM 5007 R 5091 C 5091 C 5095 C 5093 D 5052 R 5093 R 5095 D 5053 J 3001 J 2001 J 4001 J 1001 0936 RCA BOARD VM1.0 X M5015...
- Page 13 320657 SCH 5VDS R919 R904 R905 4.7K 82K/2W OP900 R906 ACDET DW900 C901 100nF/50V change to 10nF/50V PC817 DSGND D900 AC1-L AC2-N HF165FD12-HY1STF DC5V K900 5VDS P900 Relay-SPST AC-L R903 330k D902 LL4148 R930 100k 100--120V AC 60HZ R933 R941 Q908 100k R949...
- Page 14 320657 PCB C926 L901 B R901 Q918 Q919 Q930 Q931 Q928 Q929 J900 CY904 Q900 L902 TR900 C919 U903 C937 C938 L903 L905 K 902 C972 C974 C957 C958 C970 +15VDR L904 L908 T902 +87V R904 C969 C971 C973 K 900 L906 L907 J901...
- Page 15 DISPLAY 752224 SCH 1 of 2 CHANNEL LED s J3:4 J4:9 CH1 G DS1:2 J3:3 J4:10 CH1 R DS1:1 J3:2 J4:11 CH2 G DS2:2 J3:1 J4:12 CH2 R DS2:1 J3:8 J4:5 CH3 G DS3:2 1000pF 1000pF 1000pF 1000pF J3:7 J4:6 CH3 R DS3:1 J3:6...
- Page 16 DISPLAY 752224 SCH 2 of 2 +10VM +10VM CH1 / CH2 DRIVER +10VM U16:1 CH1 / CH2 LOG AMP -5VM .47µF CH1 / CH2 SUMMING AMP 6.81k L METER ADJUST 1000pF 68.1k 68.1k .1µF 2.21M 68.1k 10µF J1:18 10µF -5VM U15:2 22.1k 221k...
- Page 17 DISPLAY 752224 PCB...
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Page 18: Amp Module
AMP MODULE 320658 PCB NO SERVICEABLE PARTS REPLACE AS COMPLETE MODULE... -
Page 19: Parts List
PARTS LIST PARTS LIST (Cont’d.) INTERCONNECT MAIN PCB 320656 (Cont’d.) Ref. No. Description Part No. Ref. No. Description Part No. MAIN to FPP 1.0mm,18pin,L=420mm,64408-1827-4201 44-0-003416 D103, D324 BZT52C4V7,4.7V,350mW 33-14709-09 SMPS-MAIN PCB UL3266#14AWG 4pcs/UL3266#18AWG 2pcs,L=290mm,L=270mm,UNT001-S355-02 44-0-003417 D104, D302, D303, D305, D310, D311, 1SS355TE-17 33-40352-01 FUSE... - Page 20 R309, R310, R318, R395, R397, R425, 33W,0603,1/10W,±1%,RC0603FR-0733RL 07-93309-00 Y101 8MHz,CL=18PF,FL=20PPM 04-18001-04 R319 287W,0805,1/8W,±1%,RC0805FR-07287RL 07-92870-01 INPUT PCB 320659 MI254 RCA Board & PRE AMP Board 00-09361-00 R302 274W,0805,1/8W,±1%,RC0805FR-07274RL 07-92740-01 RCA Board & PRE AMP Board 01-1-093608 R323, R324, R332, R333, R338, R339, 10W,0603,1/10W,±1%,RC0603FR-0710RL 07-91009-00...
- Page 21 PARTS LIST PARTS LIST (Cont’d.) (Cont’d.) INPUT PCB 320659 (Cont’d.) INPUT PCB 320659 (Cont’d.) Ref. No. Description Part No. Ref. No. Description Part No. C1047, C1048, C1049, C1052, C1054, 100nK,50V,0603,X7R 26-10451-10 D3004, D4003, D4004, D5007, D6007 1N4148W-NR,SOD123 33-44148-17 C1055, C1056, C1057, C2016, C2018, 100nK,50V,0603,X7R 26-10451-10 D1001, D1002, D1005, D1006, D1009,...
- Page 22 R1050, R2050, R3050, R4050, R5007, 22KW,0805,1/8W,±1%,RC0805FR-0722KL 07-92202-01 R1040, R2040, R3040, R4040 5KW,±10%,JML 3362S-502 22-2-000228 R5023, R6007, R6023 22KW,0805,1/8W,±1%,RC0805FR-0722KL 07-92202-01 PSU PCB 320657 MI254 SMPS BOARD 00-09364-00 R1038, R2038, R3038, R4038 27KW,0603,1/10W,±1%,RC0603FR-0727KL 07-92702-00 SMPS BOARD 01-1-093605 R1066, R1070, R2066, R2070, R3066, 47KW,0805,1/8W,±1%,RC0805FR-0747KL 07-94702-01...
- Page 23 PARTS LIST PARTS LIST (Cont’d.) (Cont’d.) PSU PCB 320657 (Cont’d.) PSU PCB 320657 (Cont’d.) Ref. No. Description Part No. Ref. No. Description Part No. C919 470uF,16V,105C,±20%,6000H,8x16mm,Pitch=3.5mm,UHE1C471MPD OR 23-2-001410 R989, R988 100W,0603,1/10W,±1%,RC0603FR-07100RL 07-91000-00 C926 CD284,1000uF,10V,±20%,105W,F3.5 06-10211-13 R911, R912, R913, R914, R915, R916 1KW,0603,1/10W,±1%,RC0603FR-071KL 07-91001-00 C926...
- Page 24 PARTS LIST PARTS LIST (Cont’d.) (Cont’d.) PSU PCB 320657 (Cont’d.) DISPLAY PCB 752224 (Cont’d.) Ref. No. Description Part No. Ref. No. Description Part No. Q900 KTC2874A-AT/P,TO-92 13-2-000216 R41 R42 R90 R93 POT 1/4 HORIZ 5K OHM .5W SMD 134520 P900, P901 6.3-1,HS4-CI9120-B009V1-M032 32-26308-06 R43 R44...
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Page 25: Repacking Instructions
If a shipping carton or any of the interior part(s) 017937 Plastic foot are needed, please call or write Customer Service 400159 #10-32 x 3/4” screw Department of McIntosh Laboratory. 404080 #10 Flat washer... -
Page 26: Channel Power Amplifier
SERIAL NO . AGY1001 And Above 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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