14LK20A
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 to verify that the receiver is operating within safeAC
line input.and efficient design limitations as specified checks
should be as follows:
+115V DC REGULATOR ADJUSTMENT
The + 115V DC Adj. control (R721) is adjusted at the1. Connect an accurate high voltage meter between
factory. However, should readjustment be requiredground and anode of picture tube.
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 the receiver with 220V AC input voltage.tuned in test signal.
2. Receive a local channel.3. Enter the service mode and select the service
3. Connect positive lead of digital voltmeter to R603
TP751 (positive side) on PWB-A; negative lead toadjustment "S19" and Bus data "01" (Y-mute on).
4. The voltage should be approximately, 24.0kV (at zero
chassis ground.beam).
4. Adjust R721 to obtain a +115V DC reading.If a correct reading cannot be obtained, check circuitry
CAUTION: The reading should be within +115 ? 1V DCfor malfunctioning components. After the voltage test,
to ensure normal function and circuitry
reliability.make Y-mute off to the normal mode.
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 20.6 ? 1.5 V.
5. Apply external 26.8V 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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ACEC
SHARP
