Jvc SEAM 9 B Service Manual

Page 1

SERV'CEMANUAL .

MODEL 8 EA M9 B

D
Contents
Safety Precautions ........................ 1-1 7. Troubleshooting
1. Specifications ......................... 1-2 7-(1) General Operations ................. 1-16
2. Names of Parts and Their Functions ........... 1-3 7-(2) Drawer ......................... 1.19
3. Explanation of Technology 7-(3) 8-bit Microcomputer Peripheral Check . . . . 1-20
3-(1) Automatic Compensation 7-(4) Checking the Power Supply ........... 1-21
for Room Acoustics ................. 1-5 8. Block Diagram ..................... Insertion
3-(2) ICs developed for SEA (LM835) ......... 1-7 9. Schematic Diagram
3-(3) Pink Noise ........................ 1-7 9-(1) Overall Connection Diagram ........ Insertion
3-(4) Membrane Switch PCB ............... 1-7 9-(2) Switch PCB ................... Insertion
3-(5) FL Circuit ........................ 1-8 9-(3) SEA Amplifier PCB .............. Insertion
3-(6) Drawer Motor Drive Circuit ............ 1-8 9-(4) Main CPU PCB (1) .............. Insertion
4. Removal Procedures ..................... 1-9 9-(5) Main CPU PCB (2) .............. Insertion
5. Exploded View ....................... 1-12 9-(6) FL PCB ..................... Insertion
6. Adjustment Procedures 9-(7) Membrane Switch PCB ........... Insertion
6-(1) Distortion Adjustment (20 kHz) ........ 1-14 9-(8) Discription of Power Supply Section
'6-(2) FL Illumination Adjustment .......... . 1-14 & Semiconductors Used ........... Insertion
6-(3) Display Level Adjustment ............ 1-15 Parts List' .............. Separate-Volume Insertion
No.2745

This manual combines two single volumes, Service manual and Parts list.

Aug. 1984

Page 2

Safety Precautions

1. The design of this product contains special hardware, 5. Leakage current check

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 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 shading on the
schematics and by ( A ) on the parts list in Service
manual. The use of a substitute replacement which does
not have the same safety characteristics as the recom-
mended replacement 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/or the like to be
separated from live parts, high temperature parts, mov-
ing 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 they should be confirmed
to be returned to normal, after re-assembling.

(Safety for electrical shock hazard)

After re-assembling the product, always perform an

isolation check on the exposed metal parts of the

Products (antenna terminals, knobs, metal cabinet,

screw heads, earphone 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 (water pipe, etc.). Any leakage current must
not exceed 0.5 mA 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. Con-
nect a 1500 $2 10 W resistor paralleled by a 0.15uF
AC-type capacitor between an exposed metal part
and a- known good earth ground (water pipe, etc.).
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
__ 2 (Having lOOO ohms/volt,

or more sensitivity.)

Q &

0.15;.)c AC TYPE

I | Place this probe
w»

4>
1500,. low on each exposed
metal part.

Good Earth Ground

CHECKING YOUR LINE VOLTAGE (Except for U.S.A., Canada, Australia, U.K. and Continental Europe.)

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 operating this
equipment. The voltage selector switch is located on the rear panel.

CAUTION Before selecting the Voltage selector switch" to proper voltage disconnect the power plug.

1-1 (No. 2745)