Yamaha ax 640

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Page 1

STEREO AMPLIFIER

AX-640

SERVICE MANUAL

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IMPORTANT N0 TICE

This manual has been provided for the use of authorized Yamaha Retailers and their service
personnel. It has been assumed that basic service procedures inherant to the industry, and
more speciﬁcally Yamaha Products, are already known and understood by the users, and
have therefore not been restated.

WARNING: Failure to follow appropriate service and safety procedures when servicing
this product may result in personal injury, destruction of expensive compo-
nents and failure of the product to perform as specified. For these reasons, we
advise all Yamaha product oWners that all service required shOuld be
performed by an authorized Yamaha Retailer or the appointed service
representative.

IMPORTANT: The presentation or sale of this manual to any individual or ﬁrm does not
constitute authorization. certiﬁcation or recognition of any applicable technic-
al capabilities, or establish a principle-agent relationship of any form

The data provided is believed to be accurate and applicable to the unitls) indicated on the
cover. The research, engineering, and service departments of Yamaha are continually
striving to improve Yamaha products. Modifications are, therefore, inevitable and specifica-
tions are subject to change without notice or obligation to retroﬁt. Should any discrepancy
appear to exist, please contact the distributor's Service Division.

WARNING: Static discharges can destroy expensive components. Discharge any static
electricity your body may have accumulated by grounding yourself to the
ground bus in the unit (heavy gauge black wires connect to this buss).

IMPORTANT: Turn the unit OFF during disassembly and parts replacement. Recheck all

work before you apply power to the unit.

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I CONTENTS
TO SERVICE PERSONNEL ................. l ADJUSTMENTS . . . . .................... 5
REAR PANELS . . . ......... . ......... 'I ~ 2 IC BLOCK . . . ......................... 6
INTERNAL VIEW . ....... . . . ............ 2 WIRING . ............................. 7
SPECIFICATIONS ........ . ............. . 3 PRINTED CIRCUIT BOARD ............. 8 ~ 13
BLOCK DIAGRAM ........ . ............. 4 SCHEMATIC DIAGRAM ............. . . . . . 14
DISASSEMBLY PROCEDURES .............. 5 PARTS LIST ............... . . ...... 15 ~ 23

100346

YAMAHA

YAMAHA CORPORATION
PO. BOX 1, Hamarnatsu. Japan

2.4K-161@© Printed in Japan 90.23

Page 2

AX-640

I TO SERVICE PERSONNEL

1. Critical Components Information.
Components having special characteristics are marked A
and must be replaced with parts having speciﬁcations

equal to those originally installed. Eﬁg'gﬁg; 3% EETJECEEELEYSTER
2. Leakage Current Measurement (For 120V Model Only). ® 13- I

When service has been completed. it is imperative that F

you verify that all exposed conductive surfaces are BISTLLET 21 2

. . . INSULATING TABLE
properly insulated from supply curcmts.

- Meter impedance should be equivalent to 1500 ohm ' POLARIMTION

shunted by 0.15MB This amplifier product is equipped with a polarized
. Leakage current must not exceed 0.5mA. alternating-current lineplug (a plug having one blade
wider than the other). This plug will litinto the power
outlet only one way. This is a safety feature. (U.C Model
only)

- Be sure to test for leakage with the AC plug in both
polarities.

I REAR PANELS

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