Fisher 36 Service Manual

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PRICE $190

THIS MANUAL ALso COVERS THE E RVI E 36

37 STEREO HOME MUSIC CENTER
SERIAL NUMBERS
BEGINNING mom

The Fisher®
g 36

WORLD LEADER IN HIGH QUALITY STEREO

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CONTENTS and SERVICE TIPS

MECHANICAL DISASSEMBLY
DIAL STRINGING

HARMONIC DISTORTION TEST
SIGNAL FLOW

CHASSIS LAYOUT

01350060)

TUNER ALIGNMENT 6
TUNER 8
PREAMP/CONTROL AMP 10
POWER AMP 12
POWER SUPPLY 14

CAUTION»:

Many of these items are included only as a reminder -- they
are normal procedures for experienced technicians. Shortcuts
may be taken, but these often cause additional damage to
transistors, circuit components, or printed circuit boards.

SOLDERING: A wellvtinned, hot, clean soldering iron tip
will make soldering easier, without causing damage to the
printed circuit board or the components mounted on it.
Regular use of a sponge cleaner will maintain a clean
soldering surface. The heat available at the tip, (not the watt-
age of the iron) is important. Some SO-Watt irons reach tem-
peratures of 1,0009 F, while others will hardly melt solder.
Smalloiameter tips should be used for single solder con-
nections, pyramid and chisel tips for large areas.

Always disconnect the AC power cord from the line when
soldering. Turning the power switch OFF is not sufficient.
Power-line leakage paths, through the heating elements of the
iron, may destroy transistors.

PARTS REMOVAL: If a part is not being returned for in-
warranty factory replacement. it may be cut in half (with
diagonal cutting pliers) to make removal easier. Multiple
terminal parts, such as IF transformers, or electrolytic capaci-
tors, should be removed using special tie-soldering tips made
especially for this purpose. Removing solder from terminals,
reduces the possibility of breaking the printed circuit board
when the part is removed.

ACCIDENTAL SHORTS: A clean working area, free of metal
particles, screws, etc., is an important preventive in avoiding
servicing problems: Screws, removed from the chassis during
servicing, should be .stored in a box until needed. While a set
is operating, it takes only an instant for a bese-mollector
short to destroy a transistor (and others direct-coupled to it).
In the time it takes for a dropped screw, washer, or screw»
driver, to contact a pair of terminals (or terminal and chassis),
a transistor can be ruined.

SOLID-STATE DEVICES: Integrated Circuits contain the
equivalent of many circuit parts, including transistors, diodes,
resistors, and capacitors. The preferred troubleshooting pro-

cedure requires isolating the trouble to one stage using AC

signal tracing methods. Once the suspected stage is located
the DC voltages at the input and output leads are measured to
give an accurate indication of the operating conditions of the
IC. DO NOT use an ohmmeter, to check so." uity with the
IC mounted on the printed circuit board. Forward biasing the
internal junctions within the IC may burn out the transistors.
Do not replace a defective IC until all external resistors,
capacitors, and transformers are checked first, to prevent the
replacement IC from failing immediately due to a defect in
the connecting components. Solder and unsolder each lead
separately using a pliers or other heat sink on the lead to

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

prevent damage from excessive heat. Check that the leads are
connected to the correct locations on the printed circuit
board before turning the set on.

Whenever possible, a transistor tester should be used to de-
termine the condition of a transistor or diode. Ohrnmeter
checks do not provide conclusive data, and many even de-
stroy the junctionls) within the device.

Never attempt to repair a transistor power amplifier module
until the power supply filter-capacitors are fully discharged.

If an output or driver transistor becomes defective (opens or
shorts), always check ALL direct-coupled transistors and
diodes in that channel. In addition, check the bias pot, and
other parts in the bias network, before installing replacement
transistors. All output and driver transistors in one channel
may be destroyed it the bias network is defective. After ports
replacement, check bias for specified idling current.

In some applications, replacement of transistors must be
made from the some beta group as the original type. The
beta group is indicated by acolored marking on the transistor.
Include this information when ordering replacements.

When mounting a replacement power transistor, be sure the
bottom of the flange, mica insulator, and the surface of the
heat sink, are free of foreign matter. Dust and grit will pre-
vent flat contact, reducing heat transfer to the heat sink.
Metallic particles can puncture the insulator, cause a short.
and destroy the transistor.

Silicone grease must be used between the transistor and the
mica insulator and between the mice and the heat sink for
best heat transter. Use DowACorning DC-3. or an equivalent
compound mode for power transistor heat conduction.

Use care when making connections to speakers and output
terminals. To reduce the possibility of shorts, lugs should be
used on the exposed ends, or stranded wire should be tinned
to prevent frayed wire ends. Current in the speakers and out
put circuitry is quite high -- poor contacts, or smell wire.
can cause significant power losses. For wire lengths greater
then 30 feet, 16 AWG, or heavier, should be used.

VOLTAGE MEASUREMENTS: All voltages are measured
with the line voltage adjusted to 120 volts. All measured
voltages are a 20%. DC voltages are measured to chassis
with a VTVM, with no signal input unless otherwise noted.
AC signal voltages are measured under the conditions speci-
fied on the schematic.

ALIGNMENT PROCEDURES: DO NOT attempt realignment
unless the required test equipment is available, and the align-
ment procedure is thoroughly understood.

© COPYRIGHT 1972 FISHER RADlO ALL RIGHTS RESERVED PRINTED IN U.S.A.