Jvc RCX 250 Service Manual

Page 1

ROXQSO

JVC
SERVICE MANUAL

RC'X2 50 B/C/E/J

DIGITAL AUDIO

Area suffix
B ....... UK
C . Canada
E ....... Continental Europe
J ......... USA
Contents
Page Page
El Safety Precautions .......................................... 2 Amplifier Circuit .............................................. 24
Names of Parts, and Their functions . 4 CD Circuit ............. 25
CD Player Section ........................... 5 Wiring Connections .. 26
Cassette Section .......... 7 Location of P.C. Board Parts and Parts List
Location of Main Parts . 9 Tuner Board ................................................... 27
El Removal of Main Parts Main Board 28
Enclosure Section ........................................... 10 LCD/Switch Board . 31
CD Player Section ................ CD Board ............................................ . 32

Cassette Mechanism Section .
E] Adjustment .......
E Block Diagram

Exploded View of Mechanism Assembly .
Exploded View of Enclosure Assembly

E . 34
[E Exploded View of CD Mechanism ..

IE]

El

.36

. 40

E] Standard Schematic Diagram Packing and Packing Parts List 41

Tuner Circuit .................................................. 23 Specifications .............. .. Back Cover
No. 1847

January 1992

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RC~X250 B/C/E/J

2

a 1 Safety Precautions

l. The design of this product contains special hardware and many circuits and components specially for safety
purposes. 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.

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

3. Many electrical and mechanical parts in the product have special safety-related characteristics. These
characteristics are often not evident from visual inspection nor can the protection afforded by them necessarily
be obtained 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 Service Manual. Electrical components
having such features are identified by (A) on the schematic diagram and Parts List in Service Manual. The use
of a substitute replacement which does not have the same safety characteristics as the recommended replace-
ment part shown in the Parts List in Service Manual may create shock, fire, or other hazards.

4. The leads in the products are routed and dressed with ties, clamps, tubings. barriers and the like to be separated
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-assembling.

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, headphonejack, control shafts, etc.) to be sure the pro-
duct is safe to operate without danger of electrical shock.
Do not use a line isolation transformer during this check.
I 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 mA AC (r.m.s.).
- 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 9 10 W resistor paralleled by a 0.15 F ACrtype capacitor
between an exposed metal part and a known good earth ground.

. . A V ER
Measure the AC voltage across the resrstor With the AC @ (HgvigL-gglgg ohms/volt

VOItmeter- or more sensitivity.)
Move the resistor connection to each exposed metal 0

, . 33-
part, particularly any exposed metal part havrng a return

path to the chassis, and measure the AC voltage across 0 1 5 F AC TYPE

the resistor. Now, reverse the plug in the AC outlet and .

Place this probe
repeat each measurement. Any voltage measured must w on each exposed
not exceed 0.75 V AC (r.m.s.). 1500 n 10 w metal part.

This corresponds to 0.5 mA AC (r.m.s.).

Good earth ground

(No. 1847)

Page 19

I CD Player Adjustment

RC-X250 B/C/E/J

TP502 TP504 TP503 VR501
Adjustment of tracking on set

Fig. 4-4

0 How to operate with the CD unit conditions

(1) The CD cannot be adjusted with a DC stabilizer power
supply. For electrical supply, connect the supplied
extension cord to FW501 (Eu-pin) and FW701 (8-pin) of
the CD circuit board (VMW2321), and perform adjust-
ment after connecting to the amplifier circuit board
(VMW2321) and supplying electric power to the set.
(This is because if connection is not made to the power
supply circuit board of the amplifier, the operation of
the LSl will be erroneous due to activation time
differences in the power supply.)

(2)
(3)

(4)

The load resistance of the audio output is 28 k9.
When inserting a disc, please use the magnet clamper
used for the set or a similar object.

The table of contents can be entered by short-circuiting
the wire that connects switch $710 of the open/close
switch circuit board (VMW2321).

(No. 1847) 19