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ORDER NO.
RRV4385
A-70-K

INTEGRATED AMPLIFIER


A-70-K
A-70-S
A-50-K
A-50-S
A-50
THIS MANUAL IS APPLICABLE TO THE FOLLOWING MODEL(S) AND TYPE(S).
Model Type Power Requirement Remarks

A-70-K/-S SYXE8 AC 220 V to 230 V

A-50-K/-S SYXE8 AC 220 V to 230 V

A-50 FXE AC 110 V
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SAFETY INFORMATION

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This service manual is intended for qualified service technicians ; it is not meant for the casual do-it-
yourselfer. Qualified technicians have the necessary test equipment and tools, and have been trained
to properly and safely repair complex products such as those covered by this manual.
Improperly performed repairs can adversely affect the safety and reliability of the product and may
void the warranty. If you are not qualified to perform the repair of this product properly and safely, you
should not risk trying to do so and refer the repair to a qualified service technician.

WARNING
This product contains lead in solder and certain electrical parts contain chemicals which are known to the state of California to
cause cancer, birth defects or other reproductive harm.
B Health & Safety Code Section 25249.6 - Proposition 65




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2 A-70-K
1 2 3 4
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CONTENTS
SAFETY INFORMATION.......................................................................................................................................................... 2
1. SERVICE PRECAUTIONS .................................................................................................................................................... 4
1.1 NOTES ON SOLDERING ............................................................................................................................................... 4 A
2. SPECIFICATIONS................................................................................................................................................................. 5
2.1 ACCESSORIES .............................................................................................................................................................. 5
2.2 SPECIFICATIONS .......................................................................................................................................................... 5
3. BASIC ITEMS FOR SERVICE .............................................................................................................................................. 6
3.1 CHECK POINTS AFTER SERVICING ........................................................................................................................... 6
3.2 PCB LOCATIONS ........................................................................................................................................................... 7
3.3 JIGS LIST ....................................................................................................................................................................... 8
4. BLOCK DIAGRAM .............................................................................................................................................................. 10
4.1 OVERALL CONNECTION DIAGRAM (A-70-K/-S) ....................................................................................................... 10
4.2 OVERALL CONNECTION DIAGRAM (A-50-K/-S, A-50).............................................................................................. 12
4.3 BLOCK DIAGRAM........................................................................................................................................................ 14
5. DIAGNOSIS ........................................................................................................................................................................ 16 B
5.1 TROUBLESHOOTING.................................................................................................................................................. 16
5.2 PROTECTION CIRCUIT DESCRIPTION ..................................................................................................................... 21
5.3 IC INFORMATION ........................................................................................................................................................ 23
6. SERVICE MODE ................................................................................................................................................................. 26
7. DISASSEMBLY ................................................................................................................................................................... 27
8. EACH SETTING AND ADJUSTMENT ................................................................................................................................ 49
8.1 HOW TO CHECK THE FIRMWARE VERSION ............................................................................................................ 49
8.2 FIRMWARE UPDATING ............................................................................................................................................... 49
9. EXPLODED VIEWS AND PARTS LIST............................................................................................................................... 52
9.1 PACKING SECTION ..................................................................................................................................................... 52
9.2 EXTERIOR SECTION (A-70) ....................................................................................................................................... 54
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9.3 EXTERIOR SECTION (A-50) ....................................................................................................................................... 58
9.4 FRONT SECTION ........................................................................................................................................................ 60
10. SCHEMATIC DIAGRAM .................................................................................................................................................... 62
10.1 INPUT ASSY (1/2) ...................................................................................................................................................... 62
10.2 INPUT ASSY (2/2) ...................................................................................................................................................... 64
10.3 USB ASSY (1/2) ......................................................................................................................................................... 66
10.4 USB ASSY (2/2) ......................................................................................................................................................... 68
10.5 PHONO ASSY ............................................................................................................................................................ 70
10.6 FRONT, FUNCTION LED, VOLUME, FUNCTION SW, SECOND POWER and HEADPHONE ASSYS.................... 72
10.7 D-AMP ASSY (1/3) ..................................................................................................................................................... 74
10.8 D-AMP ASSY (2/3) ..................................................................................................................................................... 76
10.9 D-AMP ASSY (3/3) ..................................................................................................................................................... 78 D
10.10 D-AMP SUB ASSY ................................................................................................................................................... 80
10.11 SUB INPUT, POWER, CONNECTOR and AC LINE (A-70-K/-S) ASSYS ................................................................ 82
10.12 PCB GUIDE-1 - PCB GUIDE-3 (A-70-K/-S) and PCB GUIDE-4 - PCB GUIDE-10 .................................................. 84
11. PCB CONNECTION DIAGRAM ........................................................................................................................................ 86
11.1 INPUT ASSY .............................................................................................................................................................. 86
11.2 USB ASSY.................................................................................................................................................................. 90
11.3 PHONO ASSY ............................................................................................................................................................ 92
11.4 FRONT ASSY ............................................................................................................................................................. 94
11.5 FUNCTION LED, VOLUME, FUNCTION SW, SECOND POWER and HEADPHONE ASSYS.................................. 96
11.6 D-AMP ASSY and D-AMP SUB ASSY ....................................................................................................................... 98
11.7 SUB INPUT ASSY, POWER ASSY and CONNECTOR ASSY................................................................................. 100
11.8 AC LINE ASSY, PCB GUIDE-1 - PCB GUIDE-3 (A-70-K/-S) and PCB GUIDE-4 - PCB GUIDE-9 .......................... 102 E
12. PCB PARTS LIST............................................................................................................................................................ 104




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A-70-K 3
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1. SERVICE PRECAUTIONS
1.1 NOTES ON SOLDERING
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