Table of Contents
Advertisement
power cord from the AC outlet.
7. Potentials, as high as 25.0 kV (For model with 13 inch CRT) or
30.0 kV (For model with 20 inch CRT) are present when this TV set
is in operation. Operation of the TV set without the rear cover
involves the danger of a shock hazard from the TV set power
supply. Servicing should not be attempted by anyone who is not
thoroughly familiar with the precautions necessary when working
on high voltage equipment. Always discharge the anode of the
picture tube to the CRT ground of receiver before handling the
tube.
8. After servicing make the following leakage current checks to
prevent the customer from being exposed to shock hazards.
LEAKAGE CURRENT COLD CHECK
1. Unplug the AC cord and connect a jumper between the two
prongs on the plug.
2. For physically operated power switches, turn power on. Otherwise
skip step 2.
3. Measure the resistance value, with an ohmmeter, between the
jumpered AC plug and each exposed metallic cabinet part on the
receiver, such as screwheads, connectors, etc. When the exposed
metallic part has a return path to the chassis, the reading should
be between 1 M and 12 M . When the exposed metal does not
have a return path to the chassis, the reading must be infinity.
LEAKAGE CURRENT HOT CHECK
1. Plug the AC cord directly into the AC outlet.
Do not use a isolation transformer for this check.
2. Connect a 1.5 k , 10 W resistor, in parallel with a 0.15
capacitor, between each exposed metallic part on the set and a
good earth ground , as shown in Figure 1.
3. Use an AC voltmeter, with 1 k /V or more sensitivity, to measure
the potential across the resistor.
4. Check each exposed metallic part, and measure the voltage at
each point.
5. Reverse the AC plug in the AC outlet and repeat each of the above
4
F
Advertisement
Table of Contents
