Toshiba 20AR33, Service Manual

5

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.

+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 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.

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.

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.

20AR33