Panasonic C1381 - Page 3

LEAKAGE CURRENT COLD CHECK
1, Unplug the AC cord and connect a jumper between the
two prongs on the plug,
. Turn on the display power switch.
. Measure the resistance value, with an ohmmeter,
handling 26.0kV without causing X-
Radiation.
NOTE: It is important to use an accurate, periodically
calibrated high voltage meter.
1. Slide the Brightness contro! to minimum.
between the jumpered AC plug and each exposed 2. Measure the high voltage. The meter reading should
metallic cabinet part on the display, such as screwheads, indicate 24.5 kV + O.5 kV. If the meter indication
terminals, control shafts, handle bracket, etc. When an is out of tolerance, immediate service and correction
exposed metallic part has a return path to the chassis, is required to prevent the possibility of premature
the reading should be between 240 kQ and 5.2 MQ. component failure.
When exposed metal does not have a return path to the 3. To prevent an X-Radiation possibility, it is essential to
chassis, the reading must be oo,
LEAKAGE CURRENT HOT CHECK (See figure 1.)
1. Plug the AC cord into the AC outlet. DO NOT use an
isolation transformer for this check.
. Connect a 1.5 kQQ, 10 watts resistor, in parallel with a
0.15 wF capacitor, between each exposed metallic part
use the specified picture tube.
HORIZONTAL OSC. DISABLE CIRCUIT TEST
WARNING: This test must be made as a final check before
the set is returned to the customer.
. With rear cover removed, supply nominal 220V AC and
connect a host computer to the set.
on the set and a good earth ground such as a water pipe, 2. Turn on the power switch and adjust the monitor
as shown in figure 1. controls to the normal position.
3. Supply a full screen of ‘‘H” characters from the host
Leakage Current Hot- Check Circuit computer.
AC VOLTMETER 4. Turn R826 (B+ Adj.) fully counterclockwise.
5. Connect a short jumper between TP503 and ground.
6. Turn R826 (B+ Adj.) slowly clockwise.
0.15uF 7. Confirm that the picture fails out of horizontal sync.
[ese 8. If the test fails, the Horizontal Osc. Disable Circuit
Neen menae Seopa ay eect GaBUne is not operating and must be repaired.
era Mapas " : Refer to the Horizontal Oscillator Disable Circuit
Figure 1 Repair Procedure.
9. After confirmation of this Test, remove the short jumper
3. Use an AC voitmeter, with 1000 ohms/volt or more
sensitivity, to measure the potential across the resistor.
. Check each exposed metallic part, and measure the
voltage at each point.
. Reverse the polarity of the AC plug in the AC outlet
and repeat the above measurements.
. The potential at any point should not exceed 0.75 volt
RMS. A leakage current tester (Simpson Model 229 or
equivalent) may be used to make the hot checks.
Leakage current must not exceed 0.5 milliamp. If a
measurement is Outside of the specified limit, there is
and readjust B+ voltage to 100V.
This circuit must be operative before the set is returned
to the customer.
HORIZONTAL OSC. DISABLE CIRCUIT REPAIR
PROCEDURE
1.
Connect a DC voltmeter between the cathode of D553
and chassis ground of the main board. If approximately
13.6V is not present on the anode, find the cause.
Check D553 and R534.
; 2. Connect a DC voltmeter between the cathode of D555
a possibility of a shock hazard, and the monitor should ; ; :
; and chassis ground of the main board. If approximately
be repaired and rechecked before it is returned to the \ ;
13V is not present on the cathode, find the cause.
t ;
pas Check R566, R567, C560, D553 and R534.
X-RADIATION 3. Repeat step 2 procedure. If approximately 13V is f
WARNING: 1. The potential source of X-Radiation in the present on the*cathode, check D555, and IC5002. =
display is the high voltage section and the 4. When the circuit is repaired, perform the horizontal
picture tube.
2. When using a picture tube test jig for
service, ensure the jig is capable of
oscillator disable circit test again.