Commodore 1701 Service Manual page 8

SAFETY PRECAUTIONS (Continued)
8.
ISOLATION CHECK (SAFETY FOR ELECTRICAL SHOCK HAZARD)
After re-assembling the product, always perfrom an isolation check on the exposed metal parts
of the cabinet, screwheads, cable jacks, controls shafts, etc., to be sure the product is safe to
operate without danger of electrical shock.
(A)
DIELECTRIC STRENGTH TEST
The isolation between the AC primary circuit and all metal parts exposed to the user, par-
ticularly any exposed metal part having a return path to the chassis should withstand a voltage
of 1, 100V AC (r.m.s.) for a period of one second.
This method of test requires test equipment not generally found in the service trade.
*
(8)
LEAKAGE CURRENT CHECK
*
Plug the AC line cord directly into the AC outlet (do not use a line isolation transformer dur-
ing this check). Using a "Leakage Current Tester", measure the leakage current from each
exposed metal part of the cabinet, particularly any exposed metal part having a return path
to the chassis, to a known good earth ground (water pipe, etc.). Any leakage current must
not exceed 0.5mA.
ALTERNATE CHECK METHOD
Plug the AC line cord directly into the AC output (do not use a line isolation transformer
during this check). Use an AC voltmeter having 1,000 ohms per volt or more sensitivity in
the following manner. Connect a 15000 10W resistor paralleled by a 0.15JLF AC-type
capacitor between an exposed metal part and a known good earth ground (water pipe, etc.).
Measure the AC voltage across the resistor with the AC voltmeter.
Move the resistor connection to each exposed metal part, particularly any exposed metal
part having a return path to the chassis, and measure the AC voltage across the resistor.
Now, reverse the plug in the AC outlet and repeat each measurement. Any voltage measured
must not exceed 0.35V AC (r.m.s). This corresponds to O.5mA AC (r.m.s.).
CAUTION:
When troubleshooting, with power applied, use an isolation transformer and confirm that
the CRT earth wire is connected to the CRT socket board and the chassis.
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