Fisher 474 495 674 895 4020 4025 4060 Service Manual

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SERVICE MANUAL

4/ 2-Channel
Stereo Receiver

WORLD LEADER IN HIGH QUALITY STEREO

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TABLE OF CONTENTS

REQUIRED TEST EQUIPMENT . 2
HARMONIC DISTORTION CHECK . 2
FM TUNER ALIGNMENT 3
AM TUNER ALIGNMENT 4, 5
CHASSIS PARTS LIST lAll Models) 6
TUNER PARTS LIST (All Models) . . . . . . 7

TUNER SCHEMATIC (All Models)
4060/674/895 SCHEMATICS I
4060/674/895 PARTS LISTS .

LAMP BOARD PARTS LlST (4060 Only)
4020/4025/474/495 SCHEMATICS .

4020/4025/474/495 PARTS LlSTS .

REQUIRED TEST EQUIPMENT

The following test equipment is reqUired to test and align the Receiver?

Line Voltage Autotransformer or Voltage Regulator
AC DC Multimeter

Accurately Calibrated AC Voltmeter

Oscilloscope (Flat to 100 kHz Minimum)
Low-Distortion Audio Sine-Wave Generator
Harmonic Distortion Analyzer

Four (4) Load Resistors, 8-ohms, 50 Watts
(Minimum Rating)
1 Low-Distortion AM-FM Signal Generator
10.7 MHz Sweep Generator
Multiplex Generator
0 455 kHz Sweep Generator

capo V
(D (0

10,11
10,12

CAUTION:

This precision high-fidelity instrument should be serviced only by qualified personnel,
trained in the repair of transitorized equipment and printed circuitry.

HARMONIC DISTORTION CHECK

To perform the harmonic distortion check proceed as
follows:

CAUTION: Measure one channel at a time. Limit
Full Power On periods to five minutes. Use a load
resistor with a rating of at least 50 watts.

(1) Set BASS and TREBLE controls flat, SELECTOR
switch to AUX 1, and POWER/SPKRS switch to AC
OFF.

(2) Connect a low distortion sine wave signal gener-
ator between L AUX FRONT IN jack and chassis
ground. Set the generator output at 1000 Hz,
minimum output.

(3) Connect an 8~ohm load resistor between L MAIN
SPKR and COM terminals. Connect an AC VTVM,

scope, and harmonic distortion analyzer across the
8-ohm load.

(4) Set the POWER/SPKRS switch to 2-CH. Set
FRONT BALANCE (or VOLUME/BALANCE)
control(s) to full LEFT position. Turn VOLUME
control slowly up to maximum.

(5a) For Models 4020/4025/474/495, adjust the
generator output until the VTVM indicates 9 volts
RMS. The distortion analyzer should indicate less
than 1% harmonic distortion.

(5b) For Models 4060, 674, 895, adjust the genera-
tor output until the VTVM indicates 11 volts RMS.
The distortion analyzer should indicate less than 1%
harmonic distortion.

6. Repeat steps 3 through 5b for RIGHT FRONT
channels.

© COPYRIGHT 1974 FISHER HADlO I All Highls Reserved.