McIntosh MA252 Service Manual
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McIntosh MA252 Service Manual

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Table of Contents

Performance Specifications ..........................................2
Notes ...........................................................................2
Rear Panel ...................................................................3
Section Location ..........................................................4
Block Diagram .......................................................5 - 6
Interconnection Diagram ........................................7 - 8
Main/Tube Light Schematic and PCB ....................9 - 20
SERVICE MANUAL
MA252
INTEGRATED AMPLIFIER
SERIAL NO. AGA1001 And Above
CONTENTS
Control/Headphone Schematic and PCB ............21 - 24
Input Schematic and PCB ...................................25 - 28
Heatsink Schematic and PCB ..............................29 - 34
Display Schematic and PCB................................35 - 38
Terminal Schematic and PCB ..............................39 - 40
Parts List .............................................................41 - 47
Repacking Instruction ................................................49
MA252

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Summary of Contents for McIntosh MA252

  • Page 1: Table Of Contents

    MA252 MA252 INTEGRATED AMPLIFIER SERIAL NO. AGA1001 And Above CONTENTS Performance Specifications ..........2 Control/Headphone Schematic and PCB ....21 - 24 Notes ................2 Input Schematic and PCB ........25 - 28 Rear Panel ..............3 Heatsink Schematic and PCB ......29 - 34 Section Location ............4 Display Schematic and PCB........35 - 38...

  • Page 2: Performance Specifications

    +0, -3dB from 10Hz to 100,000Hz Standby: Less than 0.5 watt Sensitivity (for rated output/8 ohm load) Note: Refer to the rear panel of the MA252 for the correct voltage. High Level - 300mV unbalanced, 600mV balanced Overall Dimensions Phono - 3.0mV Width is 12 inches (30.5cm)

  • Page 3: Rear Panel

    MA252 REAR PANEL...

  • Page 4: Section Location

    SECTION LOCATIONS Top View TERMINAL DISPLAY HEATSINK Bottom View HEADPHONE INPUT MAIN TUBE LIGHT CONTROL...

  • Page 5: Block Diagram

    MA252 BLOCK DIAGRAM FROM OTHER CHANNEL OUTPUT OUTPUT (MONO) POSITIVE MUTING OUTPUT DRIVER CURRENT RIAA PHONO MM LIMITER PREAMP DIFF TUBE CASCODE POWER PREDRIVER MUTING VOLTAGE DRIVER OUTPUT LIGHTING GUARD INPUT UNBAL 1 VOLUME TONE THERMALTRAK CURRENT UNBAL 2 CONTROL...
  • Page 6 INTERCONNECT CA11 HEATSINK GRN/YEL TERMINAL MAIN DISPLAY JMP1 HEAD PHONE CONTROL INPUT HEATSINK CONVERSION JUMPER MAIN FUSE VOLTAGE JMP1 VOLTAGE 100V 17198500 100V T6.3AL 250V 110V / 120V 17198600 110V / 120V T5AL 250V 220V 17198700 220V T3.15AL 250V 230V / 240V 17198800 230V / 240V T3.15AL 250V...
  • Page 7 MA252 MAIN / TUBE LIGHT 752194 SCH 1 of 5 AC N J2:2 .1µF 150k +3.3VBU AC DETECTOR 350mA +3.3VBU PRIMARY +VBU VO UT +3.3VBU AC DET DGND 350mA FUSE J2:1 3300pF 6-32 APPLY +12VD C TO EN ER GIZE...
  • Page 8 MAIN / TUBE LIGHT 752194 SCH 2 of 5 PROGRAM / TEST USB- USB+ MAIN +3.3VBU +3.3VM +1.2VM +3.3VM +3.3VM NRST +3.3V +3.3VM 22.1k V cc +3.3VM 12.00MHz 12pF 4.7µF .1µF ERASE +3.3VM +1.2VM 12pF .1µF .1µF 10µF +3.3VM +1.2VM .1µF .1µF .1µF...
  • Page 9 MA252 MAIN / TUBE LIGHT 752194 SCH 3 of 5 -18V -12.5V J15:2 J27:2 AMPLIFIER 150k DS2 :2 150k MUTING 150k R PG J15:3 J27:3 G ND DS2 :1 22.1k J15:1 J27:1 22.1k 0.1V L PTC -55V .1µF .1µF J14:2...
  • Page 10 MAIN / TUBE LIGHT 752194 SCH 4 of 5 +175V +175V +175V +175V +12.5V -12.5V +12.5V -12.5V U23:2 .1µF .1µF 475k 221k .01µF V1:3 V3:2 12AT7 12AT7 V3:3 12AX7A MAIN +12.5V J13:6 L TUBE PREAMPLIFIER +12.5V -12.5V J13:7 -12.5V J13:9 V3:1 +12.5V -12.5V...
  • Page 11 MA252 MAIN / TUBE LIGHT 752194 SCH 5 of 5 +1 2H P +1 2H P R121 ON SEMI MMBTA55LT1G 4.75k MAIN SANYO 2SC5994-TD-E ON SEMI NE5532AND8R2G R122 R123 470µF 47.5 J22:4 R H D PH U28:2 .1µF J22:5 10µF...
  • Page 12 MAIN / TUBE LIGHT 752194 PCB...
  • Page 13 CONTROL / HEADPHONE 752195 SCH 4-40 J2:2 STBY J2:1 4-40 INPUT 1000pF 1000pF J4:1 TRIM PB J4:2 J3:4 INP A L HDPH J3:5 J4:3 J3:6 INP B AGND J3:7 J4:12 J3:8 STBY LED R HDPH J3:9 J4:9 J3:1 VOL B HDPH SW CONTROL HEADPHONE...
  • Page 14 MA252 CONTROL / HEADPHONE 752195 PCB...
  • Page 15 MA252 INPUT 752092 SCH 10µF 20.0k 10µF R BAL U1:2 R BAL 100pF 100pF J9:1 J9:4 L VOL L VOL 47pF J9:3 10µF 20.0k BAL CONV ERTER J9:2 R VOL R VOL -12.5V 10µF 20.0k INPUT 10µF J9:5 J9:6 L BAL...
  • Page 16 INPUT 752092 PCB...
  • Page 17 MA252 HEATSINK 752019 SCH 1 of 2 +55V 2.21k VOLTAGE AMP 10µF 22pF 2.21k +12V 22µF HS IN J1:17 HS IN J1:18 2.21k U1:1 100pF 47µF 33.2k U1:2 GN D J1:15 J1:16 -12V 4.99k PT C J1:3 PT C 1000pF...
  • Page 18 HEATSINK 752019 SCH 2 of 2 +55V 100pF 1.8V DRV + 4.00 in 1.2V ISO 2.350 X 1.010 DRIVER Q5:1 ISO 2.350 X 1.010 Q7:1 CURREN T LIMITER .01µF .1µF OU TPU TS 1.8k 47.5k 1.5k J2:2 .1µF B IA S A D J U STMEN T 1.5k J2:1 AD JUST R 5 1...
  • Page 19 MA252 HEATSINK 752019 PCB...
  • Page 20 DISPLAY 752020 SCH 2.74k 2.74k 2.74k PRODUCTION TEST UPDATE LOGO 2.74k 2.74k 2.74k 2.74k 2.74k 2.74k TST TXD J1:7 TST TXD TST RXD J1:6 TST RXD J1:13 J1:12 +3.3VBU J1:17 J1:18 +3.3VBU J1:1 +3.3VBU DISPLAY LIGHTS J1:11 LIGHTS 22.1 10µF .1µF FR IR J1:2...
  • Page 21 MA252 DISPLAY 752020 PCB...
  • Page 22 TERMINAL 752113 SCH and PCB .65µH L OUT + J1:1 L OUTPUT .047µF L OUT - J1:2 TERMINAL .65µH R OUT + J2:1 R OUTPUT .047µF R OUT - J2:2...

  • Page 23: Parts List

    MA252 PARTS LIST INTERCONNECT Ref. No. Description Part No. Ref. No. Description Part No. OUTPUT CONNECTOR MINI 084228 CAP MONO .1uF 50V +/- 20% X7R SMD 061365 CAP MNO 12pF 50V 5% NPOSMD0805 061364 OUTPUT CONNECTOR MINI 084228 OUTPUT CONNECTOR MINI...
  • Page 24 PARTS LIST (Cont’d.) MAIN/CNTRL/HDPHN/TUBE LT PCB 752194 (Cont’d.) Ref. No. Description Part No. Ref. No. Description Part No. CAP MONO .1uF 50V +/- 20% X7R SMD 061365 LIGHT PIPE 25.4L X 3DIA 163194 CAP 3300PF 250V UL/CSA 061312 LIGHT PIPE 25.4L X 3DIA 163194 DIODE SCHOTTKY 40V 2A SMD 070210...
  • Page 25 MA252 PARTS LIST (Cont’d.) MAIN/TUBE LT PCB 752194 (Cont’d.) Ref. No. Description Part No. Ref. No. Description Part No. RES TF 221K .125W .5% SMD0805 145140 RES SMD0805 150K 1/8W 1% 145037 RES TF 10K 1% 0.1W SMD0805 145061 RES TF 221K .125W .5% SMD0805 145140 RES SMD0805 68.1K 1/8W 1%...
  • Page 26 178195 CRYSTAL 12.00MHZ 20PF SMD 180103 CAP ELECT 470UF 16V 066508 CAP 10uF 20% 16V X5R SMD0805 061392 FIRMWARE V1.02 MA252 230270 CAP NPO 100PF 5% 200V SMD0805 061390 CAP 10uF 20% 16V X5R SMD0805 061392 CONTROL/HEADPHONES PCB 752195 CAP 10uF 20% 16V X5R SMD0805...
  • Page 27 MA252 PARTS LIST (Cont’d.) INPUT PCB 752092 (Cont’d.) Ref. No. Description Part No. Ref. No. Description Part No. DIODE ESD SUPPRESSOR SMD 070198 RES TF 1K 1% 0.1W SMD0805 145117 DIODE ESD SUPPRESSOR SMD 070198 RES TF 95.3 1% 0.1W SMD0805...
  • Page 28 PARTS LIST (Cont’d.) HEATSINK PCB 752019 (Cont’d.) Ref. No. Description Part No. Ref. No. Description Part No. CONN 18 PIN FFC RA SMD 117997 RES SMD0805 332K 1/8W 1% 145039 RES TF 620 1% 0.1W SMD0805 145119 CONN HEADER 3 POS 3.96MM 118148 CONN HEADER 2 POS 3.96MM 118147...
  • Page 29 MA252 PARTS LIST (Cont’d.) DISPLAY PCB 752020 (Cont’d.) Ref. No. Description Part No. Ref. No. Description Part No. RES SMD0805 2.74K 1/8W 1% 145025 LED GRN REV MOUNT SMD 058212 RES SMD0805 2.74K 1/8W 1% 145025 LED GRN REV MOUNT SMD 058212 RES TF 100 1% 0.1W SMD0805...
  • Page 30 NOTES...

  • Page 31: Repacking Instruction

    034579 Foam Insert (for protecting To protect the tubes during shippment, the Foam the Tubes during shipping) Insert removed from the MA252 needs to be re-insert- 041855 Warning Sheet Use the original shipping carton and interior parts only if they are all in good serviceable condition. If...
  • Page 32 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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