Sharp 21V-R70M, Service Manual

Page: 5 / 42

5
CIRCUIT PROTECTION
The receiver is protected by a 3.15A fuse (F701),
mounted on PWB-A, wired into one side of the A C
line input.
X-RADIATION PROTECTOR CIRCUIT TEST
After ser vice has been perf ormed on the horizontal
deflection system, high v olta ge system, B+ system,
test the X-Radiation pr otection cir cuit to ascer tain
proper operation as f ollo ws:
1. Apply 110~230V 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 26 ±1.1V.
5. Apply external 27V 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 v oltage is not adjustab le but m ust be c hecked
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 110~230V
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
.5
kV (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.
INSTALLATION AND SERVICE INSTRUCTIONS
Note: (1) When performing any adjustments to resistor controls and transformers, use non-mettalic
screw drivers or TV alignment tools.
(2) Before performing adjustments, the TV set must be on at least 15 minutes.
21V-R70M