Leakage Test - Sony CDP-997 Service Manual

CDP-997
(CHECKING METHODS OF LASER DIODE AND FOCUS SAFETY CHECK-OUT
SEARCH OPERATIONS)
¢ Tum the power switch ON with the condition of the disc table
closed without disc. And then watch the objective lens to
check whether the operation can be performed or not, as the
below figure shows.
After correcting the original service problem,
perform the following safety checks 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.
Front panel side
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.
@ The laser beams diffused can be observed.
1. A commercial leakage
tester, such as the
© The up and down movements of the objective lens (Twice) Simpson 229 or RCA WT-540A. Follow the
manufacturers' instructions to use these instru-
ments.
2. A battery-operated AC milliammeter. The Data
3. Measuring the voltage drop across a resistor by
The laser diode in the optical pick-up block may means of a VOM or battery-operated AC volt-
suffer electrostatic breakdown because of the poten- meter. The "'Jimit" indication is 0.75V, so
tial difference generated by the charged electrostatic 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)
load, etc. on clothing and the human body.
During repair, pay attention to electrostatic break-
down and also use the procedure in the printed
matter which is included in the repair parts.
The flexible board is easily damaged and should be
handled with care.
To Exposed Metal
Parts on Set
NOTES ON LASER DIODE EMISSION CHECK
The laser beam on this model is concentrated so as to be
focused on the disc reflective surface by the objective lens in
objective lens.
= Earth Ground
Fig. A. Using an AC voltmeter to check AC leakage.