JVC AV-20F475 Service Manual page 20

4.8 ADJUSTMENT PROCEDURE
4.8.1 CHECK ITEM
Measuring
Item
instrument
B1 VOLTAGE Signal
generator
DC voltmeter
HIGH VOLTAGE Resistor
HOLD DOWN
RESISTOR
18.0 k
3 2
4.8.2 TUNER / IF CIRCUIT
Measuring
Item
instrument
IF VCO Remote
control unit
TOO HIGH
SYNC:
AFC
FINE
4.8.3 FOCUS
Measuring
Item
instrument
FOCUS Signal
generator
1-20 (No.YA052)
Test point Adjustment part
TP-91(R927)
TP-E (IC421
Heatsink)
[MAIN PWB]
X connector
1-pin
3-pin
[MAIN PWB]
1%
1 X CONNECTOR
Test point Adjustment part
[9.VCO]
CW transf. (T111)
[MAIN PWB]
AFC STATUS
(Turn to green)
GOOD TOO LOW
YES
ON
0
Test point Adjustment part
FOCUS VR
[In HVT]
(1) Receive the black and white signal. (color off)
(2) Connect the DC voltmeter to the TP-E and TP-91.
(3) Confirm that the voltage is DC134V±2V.
• After reparing the high voltage hold down circuit. This
circuit shall be checked to operate correctly.
(1) Turn the power switch to on.
(2) Refer to the figure, connect the resistor between X
connector 1-pin and 3-pin.
(3) Make sure that the screen picture disappeares.
(4) Disconnect the power plug.
(5) Remove the resistor.
HEATER
(6) Again connect the power plug.
(7) Turn the power switch to on.
(8) Make sure that the normal picture is displayed on the
T521
screen.
4
• It must not adjust without inputting the RF signal.
(1) Receive any broadcast.
(2) Select 9.VCO from the SERVICE MODE.
(3) Change the "AFC" to "OFF" and "FINE" to "0".
(4) Confirm that the color change from "TOO HIGH" to
"TOO LOW" by CW transf. on MAIN PWB, and
check the "SYNC" is "YES".
(5) Adjust CW transf. until "GOOD" letters turns green.
And then confirm that the "SYNC" is "YES" again.
Adjustment can be done in this statement.
(6) It return the "AFC" to "ON".
(7) Push the [EXIT] key to exit the 9.VCO.
(1) Receive the cross-hatch signal.
(2) While watching at the screen, adjust the FOCUS VR
to the vertical and horizontal lines will be thinnest
and sharpest center horizontal line.
(3) Make sure that the picture is in focus even when the
screen gets darkened.
Description
Description
Description