Panasonic CT-110MA - Page 5

CT-IIOMA/IIOMCi
LEAKAGE CURRENT COLD CHECK (See figure 1.)
1, Unplug the AC cord and connect a jumper between the
two prongs on the plug.
2. Turn on the monitor's power switch.
3. Measure the resistance value, with an ohmmeter,
between the jumpered AC plug and each exposed
metallic cabinet part on the monitor, such as screw 
heads, antennas, control shafts, handle bracket, etc.
When the exposed metallic part has a return path to the
chassis, the reading should be between 240 kft and
5.2 MH.
When the exposed metal does not have a return path to
the chassis, the reading must be <» .
LEAKAGE CURRENT HOT CHECK (See Figure 1.)
1. Plug the AC cord directly into the AC outlet. Do not
use an isolation transformer for this check.
2. Connect a 1.5 kf2, 10 watts resistor, in parallel with a
0.15 m F capacitor, between each exposed metallic part
on the set and a good earth ground such as a water pipe,
as shown in figure 1.
3. Use an AC voltmeter, with 1000 ohms/volt 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 measurements.
6. The potential at any point should not exceed 0.75 volts
RMS. A leakage current tester (Simpson Model 229 or
equivalent) may be used to make the hot checks, leakage
current must not exceed 1/2 milliamp. In case a meas 
urement is out side of the limits specified, there is a
possibility of a shock hazard, and the monitor should be
repaired and rechecked before it is returned to the
WARNING. 1. The potential source of X-Radiation in TV
sets is the High Voltage section and the
picture tube.
2. When using a picture tube test jic for
service, make sure the jig is capable of
handling 25.0 kV without causing X-
Radiation.
NOTE: It is important to use an accurate, periodically
calibrated high voltage meter.
1. Turn the Bright and the Panabrite controls fully counter 
clockwise.
2. Set the SERVICE switch to SERVICE.
3. Measure the High Voltage. The upper meter (electro 
static type) reading should indicate 24 kV ± 1.0 kV.
If the upper meter indication is out of tolerance, im 
mediate service and correction is required to prevent
the possibility of premature component failure.
4. To prevent an X-Radiation possibility , it is essential to
use the specified picture tube.
5. To prevent exposure to X-Radiation, the picture tube
shield must be kept in place with power applied to the
set.
HORIZONTAL OSC. DISABLE CIRCUIT TEST
SERVICE WARNING: This test must be made as a final
check before the set is returned to the customer.
1. With rear cover removed, supply nominal 120 V AC to
the set and turn on the power switch.
2: Adjust the customer controls to normal position.
3. Short the collector and the emitter of Q801 with a
jumper wire.
Confirm that the picture tube screen blacks out (hori 
zontal oscillation stops).
4. If this does not occur, the Horizontal OSC. Disable
Circuit is not operating.
Follow the Horizontal Oscillator Disable Circuit Repair
Procedures before the set is returned to customer.
HORIZONTAL OSC. DISABLE CIRCUIT REPAIR
PROCEDURE
1) Connect a DC voltmeter between the cathode of D504
and chassis ground of the main.circuit board. If nearly
20 V is not present on the cathode, find the cause.
Check R527. D504 and C519.
2) Connect a DC voltmeter between the cathode of D505
and chassis ground of the main circuit board. If nearly
11.0 V is not present on the cathode, find the cause.
Check R518, R519 and D506.
3) Repeat step 2) procedure. If nearly 11.0 V is present on
the cathode, check IC401 , R520, C525 and D505.
4) Carefully check above specified parts, and related
cirucits and parts. When the circuit is repaired, try the
horizontal oscillator disable circuit test again.
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