Fisher 432 Service Manual

Page 1

SERVICE MANUAL

The Fishefi

432

Wfi

FM-AM
Stereo Receiver

~ Id-v

WORLD LEADER IN HIGH QUALITY STEREO

Page 2

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REQUIRED TEST EQUIPMENT

The following test equipment is required to completely test and align the Receiver:

- Line Voltage Autotransformer or Voltage
Regulator

AC DC Multimeter

Accurately Calibrated AC Voltmeter

Oscilloscope (Flat to 100 kHz Minimum)

LowDistortion Audio SineWave Generator

Harmonic Distortion Analyzer

0 Two (2) Load Resistors, 8-ohms, 250 Watts
(Minimum Rating)

LowDistortion AM-FM Signal Generator

10.7 MHz Sweep Generator

Multiplex Generator

455 kHz Sweep Generator

0...

NM

HARMONIC DISTORTION TEST

CAUTION: Limit the following tests to no more
than ten minutes each. Use 8-ohm resistors with a
minimum power rating of 250 watts when connect-
ing a load across the SPEAKERS terminals.

CONTROL SETTINGS:

Unplug the AC power cord and set the front
panel controls as follows:

BASS, TR EB LE, and BALANCE controls
to center positions

SPEAKERS switch to AC OFF
SELECTOR switch to AUX
STEREO pushbutton depressed

LOUDNESS pushbutton out
(not depressed)

VOLUME control to MIN

ONE CHANNEL DRIVEN:

(1) Connect a low distortion audio generator to
LEFT AUX IN jack. Set generator frequency to 1 kHz
and output to minimum.

(2) Connect an 8-ohm load resistor between
SPEAKERS A LEFT and COM terminals.
Connect a Harmonic Distortion analyzer and an
AC VTVM in parallel across the 8-ohm load.

(3) Connect the AC power cord and set SPEAKERS
switch to A. Turn VOLUME control to MAX.

(4) Increase generator output for 40 Watts RMS
(17.9 V across the 8-ohm load). Harmonic Distortion
Analyzer should measure 0.5% distortion or less.

(5) Repeat steps 1 through 4 for RIGHT CHANNEL.

BOTH CHANNELS DRIVEN

Connect 8-ohm load resistors across LEFT and RIGHT MAIN SPEAKERS terminals. Depress MONO"
pushbutton. Adjust generator output and BALANCE control for 40 Watts at Left and Right Channels
(17.9 Volts across the 8-ohm loads). Harmonic Distortion Analyzer should measure 0.5% distortion or

less at each channel.

CAUTION . This precision highfidelity instrument should be serviced only by qualified
- personnel, trained in the repair of transistor equipment and printed circuitry.

Page 14

TONE CONTROL AND MODE SELECTOR SCHEMATIC

TAPE I
RIGHT

TAPE 2
RIGHT

POWER
INPUT

TO LEFT CHANNEL
POWER AMPLIFIER

RIGHT CHANNEL-l

TAPE:
,- LEFT ___I FRONT PANEL
OUT IN RECORD OUTPUT
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TROIOI5 , I
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C125
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PB 2303 -2 _ I l I | I | I l H I40 I | CONTROL
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IM I I II I | I I I I TROIOIS I |__ |200 I w: /
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--OI Ol 01 0| -oI NOTES; OI
I. LINE VOLTAGE SET TO IzoVAc FOR ALL VOLTAGE MEASUREMENTS ExcEpTAs NOTED. ALL VOLTAGES t 20%. {2} Ac AND DC VOLTAGES FOR LEFT AND
PEI IN 2. DENOTEs Dc VOLTAGEs MEASURED W|TH Dc VTVM To CHASSIS WITH No INPUT SIGNAL. RIGHT CHANNELS ARE IDENTIOAL.
Elia O| ' 3._ DENOTEs lkHz SIGNAL LEvELs MEASURED WITH A: VTVM T0 CHASSIS.
L
R I _: I ._ | I 1, | 4, DENOTEs TEST PADS USED FOR PRODUCTION TESTING. I __
gIIIEII-IIOIRT UNITS I I | I | 5, ALL CAPACITOR VALUES ARE PIco FARADs UNLESS OTHERWIsE NOTED. I "
ONLY. I I I l I 6. ALL RESISTOR VALUES ARE OHMs. 15%. I'QWATT UNLESS OTHERWISE NOTED. I
I I I A I OPEN LAST l OPEN
.A - - RIIs IEo |24
TAPE I OUT '- I ' ' R 144 R 53.54
I I I Ij TONE §ONTROL 2132933332 c I28
LOUDNEss
D MODE SELECTOR SW 8
PB- 24 26
SW: sw4 SW5 sws sw7
LOW HIGH MONO STEREO MUTING
FILTER FILTER IX OFF
I3 IT
--( -
C43 AL2426-l75-2
'°°° STEREO MUTING
DEFEAT DEFEAT
(l7;
:0 . TO MPX TD TUNER
OUT P32435 PBZA34

POWER
INPUT

TO RIGHT CHANNEL
POWER AMPLIFIER