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PRODUCT SAFETY SERVICING GUIDELINES FOR AUDIO-VIDEO PRODUCTS
HOLD-DOWN CIRCUIT INFORMATION
NORMAL CONDITION
In normal condition, the DC voltage at point
proximately 4.88V through pin 1 of P1407 (HV Block).
The voltage at point
b
voltage of pin 5 of IC404 is lower than the voltage of
pin 6 (5.1V). The voltage of pin 7 is 0V and the transis-
tor Q403 is off.
ABNORMAL CONDITION
In abnormal condition, the voltage of point
higher than normal voltage. The voltage of pin 5 of IC404
is 24V and the transistor Q403 is on. Therefore, pin 1 of
IC401 receives a voltage causing the hold-down circuit
to be active. This results in the frequency of the hori-
zontal oscillation and deflection to be stopped and then
the set goes into stand-by mode.
P1407 (H.V. Block)
1
PV154 - 923-03506
is ap-
a
is approximately 4.86V. The
is much
b
a
R1455
R493
R1435
C1439
X-RAY PROTECTION
Check the X-Ray protection circuit using the following
steps. Turn the set on and input a color bar signal. Check
the B+ voltage to make sure it is correct. If B+ is 148 to
160 VDC, the power circuit is defective. To check the
operation of the hold-down circuit, apply DC 6V (+- 0.5)
to point
. If there is no raster, the set is operating
a
properly and doesn't need to be repaired.
IC404
b
5
6
C417
7
J8
ZD406
R410
(5.1V)
R491
C455
- iii -
IC401
R411
1
HPROT
Q403
ZP26/28 - SAFETY
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