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20AR21 20AR31
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 PROTECTION
The receiver is protected by a 3.15A fuse (F701), mounted on PWB-A, wired into one side of the AC line input.
HIGH VOLTAGE CHECK
High voltage is not adjustable but must be checked to verify that the receiver is operating within safe and efficient design limitations as specified checks should be as follows: 1. Connect an accurate high voltage meter between ground and anode of picture tube. 2. Operate receiver for at least 15 minutes at 110~220V AC line voltage, with a strong air signal or a properly tuned in test signal. 3. Receve a good local channel. 4. The voltage should be approximately, 25.5kV (at pictuer MAX Bright center condition). If a correct reading cannot be obtained, check circuitry for malfunctioning components.
+B DC REGULATOR CONFIRMATION
The + B DC output voltage adjustment is not included in this circuit.However, should confirmation be reguired proceed as follows. 1. Actuate receiver with 220V AC input voltage. 2. Receive a local channel. 3. Connect positive lead of digital voltmeter to C754 positive side on PWB-A ; negative lead to chassis ground. 4. Confirm this voltage reading is as below. 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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