JVC AV-14F3PX Service Manual page 23

Measuring
Item
instrument
Adjustment TV audio L OUT
of multiplex R OUT
MTS signal [AUDIO OUT]
SEPARA- generator
TION
Oscillo-
scope
L-Channel
(1 cycle)
X-RAY PROTECTION CHECK
Measuring
Item
instrument
Check of
X-RAY
PROTEC-
TION
X-RAY PROTECTOR
A
D562
R562
R563
3 2
15.0kΩ 1% 1/4W
Test point Adjustment part
7. LOW SEP.
8. HI SEP.
R-Channel
Crosstalk portion
Minimum
Test point Adjustment part
Pins 1 and 3
[X Connector
on MAIN
PWB]
FR561 D561
TO HVT
+
C561
MAIN PWB
1
X
1. Input a stereo L signal (300Hz) from the TV audio multiplex
signal generator to the Antenna terminal. (NTSC)
2. Connect the oscilloscope to the L OUT terminal of the AUDIO
OUT, and display one cycle portion of the 300Hz signal as
shown in the figure.
3. Connect the oscilloscope to the R OUT terminal of the AUDIO
OUT, and increase the voltage sensitivity of the oscilloscope.
4. Select the sub menu screen SOUND from the SERVICE
MENU.
5. Select 7. LOW SEP. with the MENU 1/4 key, and confirm its
initial setting value.
6. Adjust 7. LOW SEP. so that the peak-to-peak level of the 300Hz
signal becomes minimum, with the MENU 2/3 key.
7. Change the input signal to 3kHz, and similarly adjust for 8. HI
SEP. by repeating steps 2 to 6.
Prepare the following resistor.
Ω ±
15.0k 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 15.0kΩ 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. 56083
AV-14F3PX
Description
Description
23