SAFETY CHECK-OUT
NOTES ON HANDLING THE OPTICAL PICK-UP BLOCK
OR BASE UNITAfter correcting the original service problem, perform the follow-
ing safety checks before releasing the set to the customer:
The laser diode in the optical pick-up block may suffer electrostaticCheck the antenna terminals, metal trim, Ometallized� knobs, screws,
break-down because of the potential difference generated by the
and all other exposed metal parts for AC leakage. Check leakage as
charged electrostatic load, etc. on clothing and the human body.described below.
During repair, pay attention to electrostatic break-down and also
use the procedure in the printed matter which is included in theLEAKAGE
repair parts.
The AC leakage from any exposed metal part to earth Ground and
The flexible board is easily damaged and should be handled withfrom all exposed metal parts to any exposed metal part having a
care.
return to chassis, must not exceed 0.5 mA (500 microampers). Leak-
age current can be measured by any one of three methods.
NOTES ON LASER DIODE EMISSION CHECK
1. A commercial leakage tester, such as the Simpson 229 or RCA
WT-540A. Follow the manufacturersO instructions to use these
The laser beam on this model is concentrated so as to be focused on
instruments.
the disc reflective surface by the objective lens in the optical pick-2. A battery-operated AC milliammeter. The Data Precision 245
up block. Therefore, when checking the laser diode emission, ob-
digital multimeter is suitable for this job.
serve from more than 30 cm away from the objective lens.3. Measuring the voltage drop across a resistor by means of a VOM
or battery-operated AC voltmeter. The Olimit� indication is 0.75
LASER DIODE AND FOCUS SEARCH OPERATIONV, so analog meters must have an accurate low-voltage scale.
CHECK
The Simpson 250 and Sanwa SH-63Trd are examples of a pas-
sive VOM that is suitable. Nearly all battery operated digital
Carry out the OS curve check� in OCD section adjustment� and check
multimeters that have a 2V AC range are suitable. (See Fig. A)
that the S curve waveform is output four times.
To Exposed Metal
Parts on Set
AC
0.15?F1.5kWvoltmeter
(0.75V)
Earth Ground
Fig. A. Using an AC voltmeter to check AC leakage.
� 6 � |
ACEC
