Sharp XFlat 20F650 Service-Handbuch - Seite 7

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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 4A fuse (F701),

mounted on PWB-A, wired into one side of the AC

line input.

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 120V 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 P603 pin3 and make

sure that the voltmeter reads 19.8 ±1.1V.

5. Apply external 25.5V DC at P603 pin3 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 P603 pin1 and P603 pin2.

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.

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 120V AC

line voltage, with a strong air signal or a properly

tuned in test signal.

3. Enter the service mode and set Y-mute ON by using

Service R/C.

4. The voltage should be approximately 28.7kV (at zero

beam).

If a correct reading cannot be obtained, check circuitry

for malfunctioning components. After the voltage test,

make Y-mute off to the normal mode.

20F650