Jvc MXG 850 V Service Manual

Page 2

MX-G950V/MX-G880V
MX-G850V/MX-G750V

-Safety Precautions

1. This design of this product contains special hardware and many circuits and components specially for safety

. Alterations of the design or circuitry of the product should not be made. Any design alterations of the product

. Many electrical and mechanical parts in the products have special safety-related characteristics. These

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

. Leakage currnet check (Electrical shock hazard testing)

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.

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.

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 (AM 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.

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 reassembling.

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.).

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 9 10W resistor paralleled by a 0.1511 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 (HavingiOOO
voltmeter. ohms/volts,

Move the resistor connection to each exposed metal part, 0"0'9 sens"'V"Yl

particularly any exposed metal part having a return path to
the chassis, and meausre the AC voltage across the resistor.

0.1511 F AC TYPE

Now, reverse the plug in the AC outlet and repeat each -"_ Place this
measurement.IVoltage measured any must not exceed 0.75 V w, . r , :gézeeigosed
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. chassis. Therefore, pay attention to

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.

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 (I), diode (-) and ICP (.) or identified by the "A"
mark nearby are critical for safety.

(This regulation does not correspond to J and C version.)

Page 20

MX-G950V/MX-G880V
MX-G850V/MX-G750V

11.Check whether the lifter unit stopper has been caught Stopper
into the hole at the section e" of CD tray assembly as
shown in Fig.5.

12. Make sure that the driver unit elevator is positioned as
shown in Fig.6 from to the second or fifth hole on the
left side face of the CD changer mechanism assembly.

[Caution] In case the driver unit elevator is not at above
position, set the elevator to the position as
shown in Fig.7 by manually turning the pulley
gear as shown in Fig.8.

13. Manually turn the motor pulley in the clockwise
direction until the lifter unit stopper is lowered from the
section "e of CD tray assembly(See Fig.8).

14. Pull out all of the three stages of CD tray assembly in
the arrow direction "f until these stages stop

(See Fig.6).

15. At the position where the CD tray assembly has
stopped. pull out the CD tray assembly while pressing
the two pawls "g and g' " on the back side of CD tray
assembly(See Fig.9). In this case, it is easy to pull out
the assembly when it is pulled out first from the stage
CD tray assembly.

Chassis assembly

CD tray assembly

Refer to Fig.7

Pulley gear

Motor pulley

Fig.8

1-20

Page 28

MX-G950V/MX-G880V
MX-G850V/MX-G750V

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.
. Attenuator impedance : 6000hm
. Electronic voltmeter
. Frequency counter
. Wow flutter meter
. Test tape
VT712 : For Tape speed and wow flutter ( 3kHz)
VT710 : Head azimuth
VT724 : For Reference level (1 kHz)
7. Blank tape
TAPE LAC-225
8. Torque gauge : For play and back tension
Forward ;TW2111A, Reverse ;TW2121A
Fast FonNard and Rewind ;TW2231A
9. Test disc
: CTS-1000(12cm),GRG-121 1 (8cm)
10. Jitter meter

0301-th

Measurement conditions

Power supply voltage
AC1 10V/127V/220V/230V~240V L, adjustable

Measurement

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

1-28

Radio input signal

AM modulation frequency :400Hz
Modulation factor : 30%

FM modulation frequency :400Hz
Frequency displacement 222.5kHz

Frequency Range
AM 531kHz~1710kHz
FM 87.5MHz~108MHz

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

ECHO :OFF

Precautions for measurement

1.Apply 30pF and 33kohm to the IF sweeper output
side and 0.082 F 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.