Jvc MXG 70 UW Service Manual

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SERVICE MANUAL

COMPACT COMPONENT SYSTEM

Area Suffix
M X-G7o A ---------------- Australia
UP ---------------- Korea
US ------------- Singapore
UW---- Brazil,Mexico,Peru
UY ------------- Argentina

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SP-MXG70 CA-MXG70 SP-MXG70 [filfigfi

(No MIC jack and MIC LEVEL volume for A,UP,UY ver.) DIGITAL AUDIO
Contents
Safety precautions - 1-2 Flow of functional operation
Important for laser products ------------ 1-3 until TOC read ----------- 1-29
Preventing static electricity ------------- 1-4 Maintenance of laser pickup ------------ 1-30
Disassembly method --------------------- 1-5 Replacement of laser pickup ------------ 1-30
Adjustment method ----------------------- 1-25 Description of major ICs ----------------- 1-31 ~49

This service manual is printed on 100% recycled paper. No_20986

COPYRIGHT (9) 2001 VICTOR COMPANY OF JAPAN, LTD.

Jun. 2001

Page 2

MX-G70

-Safety Precautions

1. This 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 manufacturer's 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 (/t\,) 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 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 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 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.).

. 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 Q10W resistor paralleled by a 0.1 51.1 F 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 a (Having1000
voltmeter. ohms/volts,

Move the resistor connection to each exposed metal part, c more sens'l'V'W)

particularly any exposed metal part having a return path to
the chassis, and measure the AC voltage across the resistor. 0'15: AC TYPE

Now, reverse the plug in the AC outlet and repeat each -"| Placehis
measurement.IVoltage measured any must not exceed 0.75 V W . ~ ggiieeigosed
AC (r.m.s.). This corresponds to 0.5 mA AC (r.m.s.). 15009 10W metal part.
Good earth ground
- Warning A CAUTION
1.This equipment has been designed and manufactured to meet international safety standards. Burrs formed during molding may

2. it is the legal responsibility of the repairer to ensure that these safety standards are maintained. be left over on some parts of the
3. Repairs must be made in accordance with the relevant safety standards.
4. It is essential that safety critical components are replaced by approved parts. such burrs in the case of

5. If mains voltage selector is provided, check setting for local voltage. preforming repair of this system.

chassis. Therefore, pay attention to

In regard with component parts appearing on the silk-screen printed side (parts side) of the PWB diagrams, the
parts that are printed over with black such as the resistor (-), diode (h) and ICP (Q) or identified by the (N
mark nearby are critical for safety.

When replacing them, be sure to use the parts of the same type and rating as specified by the manufacturer.
(Except the J&C version)

Page 25

Adjustment method

Measurement instruments required
for adjustment

1. Low frequency oscillator,
This oscillator should have a capacity to output 0st
to 6000hm at an oscillation frequency of 50Hz-20kHz.

2. Attenuator impedance : 6000hm

3. Electronic voltmeter

4. Frequency counter

5. Wow flutter meter

6. Test tape

VTT712 : For Tape speed and wow flutter ( 3kHz)

VTT724 : For Reference level (1kHz)

TMT7036 : For Head angle(10kHZ),Play back frequency
characteristics(1kHz).and dubbing frequency
characteristics(63,1,10kHz)

Because of frequency-mixed tape with 63,1k,10k and

14kHz(250nWb/m -24dB).

Use this tape together with a filter.

7. Blank tape
TAPE 1: AC-225.

8.Torque gauge : For play and back tension
Forward :TW2111A, Reverse :TW2121A
Fast Forward and Rewind ;TW2231A

9. Test disc
: CTS-1000(12cm),GRG-1211(80m)

10. Jitter meter

Measurement conditions

Power supply voltage

A0240V(50Hz): A model

AC220V(50Hz): URUY model

AC1 10/127/230-240V(50/60Hz): US,UW model

Measurement

output terminal : Speaker out
:TP101(Mesuring forTUNER/DECK/CD)
:Dummy load Gohm

MX-G70

Radio input signal

AM modulation frequency : 400Hz

Modulation factor : 30%

FM modulation frequency : 400HZ

Frequency displacement : 22.5kHz

Frequency Range
AM 531 kHz~1710kHz : UPUS,UW.UY model
522kHz~1629kHz : A model

FM 87.5MHZ~108MH2

Standard measurement positions of volume
and switch

Power : Standby (Light STANDBY Indicator)
Sub woofer VOL. : Minimum

Sound mode :OFF

Main VOL. : 0 Minimum

Traverse mecha set position : Disc 1

Mic MIX VOL : MAX (Only US,UW ver.)

ECHO : OFF

Precautions for measurement

1. Apply 30pF and 33kohm to the IF sweeper output
side and 0.082 11F and 100kohm in series to
the sweeper input side.

2.The IF sweeper output level should be made as
low as possible within the adjustable range.

3. Since the IF sweeper is a fixed device, there is
no need to adjust this sweeper.

4. Since a ceramic oscillator is used, there is no need
to perform any MPX adjustment.

5. Since a fixed coil is used. there is no need to adjust
the FM tracking.

6. The input and output earth systems are separated.
In case of simultaneously measuring the voltage
in both of the input and output systems with an
electronic voltmeter for two channels, therefore.
the earth should be connected particularly.

7. In the case of BTL connection amplifier, the minus
terminal of speaker is not for earthing. Therefore.
be sure not to connect any other earth terminal
to this terminal.This system is of an OTL system.

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