Jvc AXMX 70 BK Service Manual

Page 2

AX-MX7OB K

-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. Services 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 manufacturers warranty and will further relieve the manufacture of responsibility
for personal injury or property damage resulting therefrom.

3. Many electrical and mechanical parts in the products 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 shading on the schematics and by (A) on the Parts
List in the Service Manual. The use of a substitute repalcement which does not have the
same safety characteristics as the recommended replacement parts shown in the Parts List of
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 currnet 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,
contorl 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 parts 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 0.5mA 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 3 1,5000 10 W
resistor paralleled by a 0.15 pF 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 voltmeter. E 2T;%§°°_ . g
Move the resistor connection to each exposed o 0_ WWW sensmvflyJ
metal part, particularly any exposed metal part
having a return path to the chassis, and 1115/5 AC TYPE
meausre the AC voltage across the resistor. |--
Now, reverse the plug in the AC outlet and [-l Flue this
4... probe on

repeat each measurement. Any voltage - vv each exposed
measured must not exceed 0.75VAC (r.m.s.). 150°01°W metal part.
This corresponds to 0.5 mA AC (r.m.s.). Good earth ground

- Warning

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

2. It is the legal responsibility of the repairer to ensure that these safety standards are
maintained.

3. 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.

U135

1-2 (No. 20244)

Page 64

FX~MX7DBK

FM/AM Tuner Alignment Procedures

mos g Q :52 I 105
II N

7107

TP104 -_ TPZUZ

I IE: IECHECK

chs 710 T102

4 TC106

@ Q 1'le
FRONT I I

T103 EN D
Tl V-TUNE

I DISCHARGE

When dischargeing the backup, shortcircuit the two terminals of TP104.

1. FM section
I FM oscillator
(I) Set the frequency display to 108.0M'Hz.
(2) Confirm that the FM inter-station noise is received.
(3) Confirm that the voltage of test point TP101' is
8.0Vi2.0V.
(4) Set the frequency display to 87.5MHz" and confirm
the voltage of test point TPlOl is 1.6Vil.0V.

I FM detector coil : T105
(1) Connect a digital voltmeter to test point W102,

and reoeive to "100.1MHi signal with SSG at 70dB.

(2) Adjust T105 so that the digital voltmeter reads
0 i 1.5mV.

2. MW section
Note ( ): Australia.the U.K.and
Continental Europe
{ }: Channel space 9kHz for
universal version
l J -. Channel space mm: for
universalversion
l ]: America,Canada

I MW oscillator : T103

(1) Set the frequency display to (52211112)
(531nm l530kHzJ [530mllond confirm that the
voltage of test point TPlOl is (0.9Vi0.2V)
{1.0Vi0.2v} l1.0V:l:0.2Vl [LoviOZV].

(2) Set the frequency display to (lGZQIHz)
(1.602%) T lGOOkHz J [l'IIOIHl] and confirm that
the voltage of heat point TP101 is (7.5V :l: 0.8V)(
7.2V: 0.7V) l 7.2V: 0.7V J [8.0Vi0.8Vl.

(3) If its voltage exceed: the allowance. adjust T108 to
obtain the voltage.

1-10 (No. 20245)

I MW antenna coil :T101
(1) Connect a loop antenna to the AM Loop
terminal on the rear pmeL
(2) Adjust T101 to obtain the best receiving
sensitivity on 600kHz or 603kl-lz .
I MWantenna trimmerzTC105
(1) Adjust TC105 to obtain the best receiving
sensitivity on l400kHzor1404kl-lz.

3. LW section(for Long Wave Version)
Note : l l for italy

I LW oscillator : T104
(1) Set the frequency display to 144m: and adjust
T104 so that the Voltage of TPlOl
becomes 0.8V: 0.1V .
(2) Set the frequency display to 353mz[290kl'lz]
and confirm that the voltage oftest point 1le
becomes 8.0V: 0.9Vl5.7V1E 0.6V ] .

I LW antenna coil : T102
(1) Connect a loop antenna to the AM Loon
terminnl on the rear panel.
(2) Adjust T102 to obtain the best receiving
sensitivity on IMXHZIIGAHIZ].

I LW antenna trimmer: TC106
(1) Acuusv. 10106 to obtain the best receiving
sensitivity on853kI-Iz [ 245132] .
X Alternately adjust T102 and TC1 06 so that
each sendtivity becomes maximum.