Jvc AX 90VBK Service Manual

Page 1

JVC
ERVICE MANUAL

AX-QOVBK

MODEL No. AX'QOVBK

Contents

Page
Safety Precautions .................................................... 1-2
Instruction Book V
Block Diagram ........................................................... 1-3
Technical Explanations .............................................. 1-5
Removal Procedures .................................................. 1-9
Adjustment Procedures ............................................. 1-10
Functions of ICs on the Pre-

Amplifier PC Board ................................................ 1-1 1

Page

Handling precautions of LCD

panels ...................

................................................ 1-11

Servicing Method for AWG ,2: 20
wires with Clamping Terminals ............................ 1-12
Internal Block Diagrams of

Major le ..............
Parts List ...................

Schematic Diagram
Connection Diagram

................................................ 1 -1 3
............... Separate-volume Insertion

......................................... Insertion

No. 2938
Jun. 1986

Page 2

Safety Precautions

I. The design of this product contains special hardware and

many circuits and components specially for safety pur-
poses.

For continued protection, no changes should be made to
the original design unless authorized in writing by the
manufacturer. Replacement parts must be identical to
those used in the original circuits. Service should be
performed by qualified personnel only.

. Alterations of the design or circuitry of the product
should not be made. Any design alterations or additions
will void the manufacturers warranty and will further
relieve the manufacturer of responsibility for personal
injury or property damage resulting therefrom.

. Many electrical and mechanical parts in the product
have special safety-related characteristics. These charac-
teristics are often not evident from visual inspection nor
can the protection afforded by them necessarily be ob-
tained by using replacement components rated for
higher voltage, wattage, etc. Replacement parts which
have these special safety characteristics are identified in
the parts list of the service manual. Electrical compo-
nents having such features are identified by shading on
the schematics and by ( A) on the parts list in the
service manual. The use of a substitute replacement
which does not have the same safety characteristics as
the recommended replacement part shown in the parts
list in the service manual may create shock, fire, or other
hazards.

. The leads in the products are routed and dressed with
ties, clamps, tubings, barriers and the like to be sepa-
rated from live parts, high temperature parts, moving
parts and/or sharp edges for the prevention of electric
shock and fire hazard.

When service is required, the original lead routing and
dress should be observed, and it should be confirmed
that they have been returned to normal, after re-assembl-

mg.

5. Leakage current check

(Electrical shock hazard testing)

After re-assembling the product, always perform an

isolation check on the exposed metal parts of the

product (antenna terminals, knobs, metal cabinet,

screw heads, headphone jack, control shafts, etc.) to be

sure the product is safe to operate without danger of

electrical shock.

Do not use a line isolation transformer during this check.

0 Plug the AC line cord directly into the AC outlet.
Using a "Leakage Current Tester", measure the
leakage current from each exposed metal part of the
cabinet, particularly any exposed metal part having a
return path to the chassis, to a known good earth
ground. Any leakage current must not exceed 0.5
AC(r.m.s.).

0 Alternate check method
Plug the AC line cord directly into the AC outlet.
Use an AC voltmeter having 1,000 ohms per volt or
more sensitivity in the following manner. Connect a
1,500 $2 10 W resistor paralleled by a 0.15 uF AC~
type capacitor between an exposed metal part and a
known good earth ground.
Measure the AC voltage across the resistor with the
AC voltmeter.
Move the resistor connection to each exposed metal
part, particularly any exposed metal part having a
return path to the chassis, and measure the AC
voltage across the resistor. Now, reverse the plug in
the AC outlet and repeat each measurement. Any
voltage measured must not exceed 0.75 V AC(r.m.s.).
This corresponds to 0.5 mA AC(r.m.s.).

AC VOLTMETER
Z (Having 1000 ohms/volt,
or more sensitivity.)

-C O-

015 VF AC TYPE

P -ll-
L A m 4
b 15005} low

Good Earth Ground

Place this probe
> on each exposed
metal part.

CHECKING YOUR LINE VOLTAGE (Except for U.S.A., Canada. U.K., Continenual Europe and Australia) Kl
Before inserting the power plug, please check this setting to see that it corresponds with the line voltage
in your area. If it doesnt be sure to adjust the voltage selector switch to the proper setting before operat-
ing this equipment. The voltage selector switch is located on the rear panel.

CAUTION: Before setting the "Voltage selector switch" to the proper voltage, disconnect the power plug.

7-50)!

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102.

1-2 (No. 2938)