Servicing Notes - Sony CFD-ZW755 Service Manual

SAFETY CHECK-OUT
After correcting the original service problem, perform the
following safety check before releasing the set to the customer :
Check the antenna terminals, metal trim, "metallized" knobs,
screws, and all other exposed metal parts for AC leakage. Check
leakage as described below.
LEAKAGE TEST
The AC leakage from any exposed metal part to earth ground and
from all exposed metal parts to any exposed metal part having a
return to chassis, must not exceed 0.5mA (500 microampers).
Leakage current can be measured by any one of three methods.
1. A commercial leakage tester, such as the Simpson 229 or RCA
WT-540A. Follow the manufacturers' instructions to use these
instruments.
2. A battery-operated AC milliammeter. The Data Precision 245
digital multimeter is suitable for this job.
3. Measuring the voltage drop across a resistor by means of a VOM
or battery-operated AC voltmeter. The "limit" indication is 0.75V,
so analog meters must have an accurate low-voltage scale. The
Simpson 250 and Sanwa SH-63Trd are examples of a passive
VOM that is suitable. Nearly all battery operated digital
multimeters that have a 2V AC range are suitable. (See Fig. A)
To Exposed Metal
Parts on Set
0.15 µF
Fig. A. Using an AC voltmeter to check AC leakage.
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SECTION 1

SERVICING NOTES

AC
1.5kΩ voltmeter
(0.75V)
Earth Ground
CHUCK PLATE JIG ON REPAIRING
On repairing CD section, playing a disc without the CD lid, use
Chuck Plate Jig.
• Code number of Chuck Plate Jig : X-4918-255-1
LASER DIODE AND FOCUS SEARCH OPERATION
CHECK
1. Turn on POWER button and press CD button to CD
position.
2. Open the CD lid.
3. Turn on S901 as following figure.
4. Confirm the laser diode emission while observing the
objecting lens. When there is no emission, Auto Power
Control circuit or Optical Pick-up is broken.
Objective lens moves up and down three for focus search.
– 3 –
Insert a precision
screw driver and push
SWITCH (S901)