Jvc TDV 621 Service Manual 2

Page 1

JVI:
SERVIE MANAL

A/B/C/E/G/J/U

Contents

Page Page
Safety Precautions ............................................... 2 7 Location of BC. Board Parts ............................ 35
Instruction Book (Extract) ...................................... 4 Power/Mechanism Control Board ...................... 35
1 Location of Main Parts .................................... 22 Main Board .................................................... 36
2 Removal of Main Parts .................................... 24 Display/Switch Board ...................................... 4O
3 Main Adjustments ........................................... 26 . 8 Exploded View of Mechanism Assembly ............ 42
4 Block Diagram ................................................ 31 9 Exploded View of Enclosure Assembly .............. 44
5 Standard Schematic Diagram ............................ 31 10 Accessories .................................................... 47
6 Wiring Connections ......................................... 34 11 Packing ............................................. Back Cover

No. 4299

February 1989

Page 2

2

-Safety Precautions

1.

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.

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. '

. 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.

. 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.

. 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 pro-
duct 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 mA AC lr.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 (I 10 W resistor paralleled by a 0.15 uF AC -type capacitor

between an exposed metal part and a known good earth ground. AC VOLTMETER
Measure the AC voltage across the resistor with the AC [Having 1000 ohms/v0",
voltmeter. or more sensitivity.)
Move the resistor connection to each exposed metal .0

part, particularly any exposed metal part havmg a return 0.15 F AC TYPE

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.).

-i

Place this probe
1500 9 10 W metal part.

Good earth ground

- Warning

. This equipment has been designed and manufactured to meet international safety standards.

wewws

on each exposed

It is the legal responsibility of the repairer to ensure that these safety standards are mainteined.
Repairs must be made in accordance with the relevant safety standards.

It is essential that safety critical components are replaced by approved parts.

If mains voltage selector is provided, check setting for local voltage.

(No. 4299)