JVC AV-21F1P Service Manual page 22

AV-21F1P
X-RAY PROTECTION CHECK
Measuring
Item
instrument
Check of
X-RAY
PROTEC-
TION
X-RAY PROTECTOR
A
D562
R562
R563
3
17.2kΩ 1% 1/4W
22
Test point Adjustment part
Pins 1 and 3
[X Connector
on MAIN
PWB]
FR561 D561
TO HVT
+
C561
MAIN PWB
2 1
X
Prepare the following resistor.
Ω ±
17.2k 1% 1/4W
1. Turn on the power and receive any signal.
2. Connect the resistor between pins 1 and 3 of the X connector
on the Main PW Board.
3. Make sure that the picture disappears.
4. Unplug the AC power cord.
5. Disconnect the resistor from the X connector.
6. Plug the AC power cord and make sure that the picture ap-
pears normally.
X-Ray Protector Operation:
Normally the voltage at point "A" does not exceed the Zener volt-
age of D562. (The voltage at point "A" will be determined by divid-
ing the voltage from HVT (FBT) by R562 and R563.)
When you connect a resistor of 17.2kΩ or less in parallel with
R562, the voltage at point "A" is increased, D562 turns ON, and
the X-ray protection circuit is activated. Once it is activated, you
need to unplug the AC power cord to restore the X-ray protection
circuit.
No. 56033
Description