20PL83
INSTALLATION AND SERVICE INSTRUCTIONS
Note: (1) When performing any adjustments to resistor controls and transformers use non-metallic
screwdrivers or TV alignment tools.
(2) Before performing adjustments, the TV set must be on at least 15 minutes.
CIRCUIT PROTECTIONHIGH VOLTAGE CHECK
The receiver is protected by a 3.15A fuse (F701),High voltage is not adjustable but must be checked
mounted on PWB-A, wired into one side of the Ato verify that the receiver is operating within safCe
line input.and efficient design limitations as specified checks
should be as follows:
+B DC REGULATOR CONFIRMATION
The + B DC output voltage adjustment is not inc1.ludedConnect an accurate high voltage meter between
in this circuit.However, should confirmation beground and anode of picture tube.
reguired proceed as follows.2. Operate receiver for at least 15 minutes at 110~220V
AC line voltage, with a strong air signal or a properly
1. Actuate receiver with 220V AC input voltage.tuned in test signal.
2. Receive a local channel.3. Receve a good local channel.
3. Connect positive lead of digital voltmeter to C754
positive side on PWB-A ; negative lead to chassis4. The voltage should be approximately, 25.5kV (at
pictuer MAX Bright center condition).
ground.If a correct reading cannot be obtained, check circuitry
4. Confirm this voltage reading is as below.for malfunctioning components.
CAUTION: The reading should be within +130.0 ? 2.0V
DC to ensure normal function and circuitry
reliability.
X-RADIATION PROTECTOR CIRCUIT TEST
After service has been performed on the horizontal
deflection system, high voltage system, B+ system,
test the X-Radiation protection circuit to ascertain
proper operation as follows:
1. Apply 220V AC using a variac transformer for accurate
input voltage.
2. Allow for warm up and adjust all customer controls
for normal picture and sound.
3. Receive a good local channel.
4. Connect a digital voltmeter to TP653 and make sure
that the voltmeter reads 21.4 ? 1.5 V.
5. Apply external 27.9V DC at TP653 by using an
external DC supply, TV must be shut off.
6. To reset the protector, unplug the AC cord and make
a short circuit between TP651 and TP652. Now make
sure that normal picture appears on the screen.
7. If the operation of the horizontal oscillator does not
stop in step 5, the circuit must be repaired before the
set is returned to the customer.
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