JVC AV-25MT35/P Service Manual page 16

4.7 ADJUSTMENT PROCEDURE
4.7.1 B1 VOLTAGE
Measuring
Item
instrument
B1 VOLTAGE Signal
check generator
DC voltmeter
4.7.2 FOCUS ADJUSTMENT
Measuring
Item
instrument
FOCUS Signal
adjustment generator
4.7.3 IF CIRCUIT ADJUSTMENTS
Measuring
Item
instrument
IF VCO Remote
check control unit
VCO (CW)
TOO HIGH
ABOVE REFERENCE
JUST REFERENCE
BELOW REFERENCE
TOO LOW
DELAY POINT Remote
(AGC control unit
TAKE-OVER)
adjustment
Adjustment item
2. DELAY POINT
(AGC TAKE-OVER)
1-16 (No.YA275)
Test point Adjustment part
B1 (pin 1)
GND (pin 5)
[CN00X
connector in
MAIN PWB]
Test point Adjustment part
FOCUS VR
[In HVT]
Test point Adjustment part
[1. IF]
1. VCO (CW)
Receiving frequency
. MHz
YELLOW
DISPLAY : EXIT
[1. IF]
2. DELAY POINT
Initial setting value
NTSC 3.58 OTHERS
VHF UHF VHF UHF
28* 28* 28* 28*
Description
(1) Receive a PAL black and white signal.
(2) Connect a DC voltmeter between B1 and GND
(between pins 1 and 5 of the connector CN00X).
(3) Make sure that the voltage is DC134.5V ± 2V.
Description
Notes:
• Set PICTURE MODE (VSM) to "BRIGHT".
• The final adjustment of CONVERGENCE must be
done after the FOCUS adjustment. (CONVERGENCE
is affected by the FOCUS adjustment.)
If any aeviation in CONVERGENCE is found, PURITY
must be adjusted to restore the convergence.
(1) Receive a PAL crosshatch signal.
(2) Adjust the FOCUS VR so that the vertical and
horizontal lines will be clear and in fine detail on the
screen.
(3) Make sure that the picture is in focus even when the
screen gets darkened.
Description
Note:
• Under normal conditions, no adjustment is required.
(1) Receive a PAL broadcast signal.
(2) Select 1. IF from the SERVICE MENU.
(3) Select 1. VCO.
(4) Check the characters colour of the JUST REFERENCE
displayed to yellow.
(5) Press the [DISPLAY] key three times to return to
normal screen.
(1) Receive a PAL black and white broadcast signal (colour off).
(2) Select 1. IF from the SERVICE MENU.
(3) Select 2. DELAY POINT.
(4) Adjust in order to eliminate any noise or beat from
the image. Any increase above the initial value
produces the noise and any decrease below it
produces the beat.
(5) Press the [DISPLAY] key three times to return to the
normal screen.
(6) Turn to other channels and make sure that there are
no irregularities.