Sharp LC-20B2UA Service Manual page 13

4. Adjustments
Adjustment
1 B+ Adjustment
(R3760)
2 Inch Size setup
(If E 2 PROM is replaced)
(IC2004)
3 Common-bias adjustment
4 TAMP adjustment
5 White balance adjustment
6 Checking and modifying
the settings adjustment
2
(If E PROM is replaced)
Adjusting conditions
1. Connect the DC voltmeter to
pin 2 of P3702.
1. Go to the adjustment mode.
1. Receive a B/W channel.
2. Go to the adjustment mode.
3. Select the "COM BIAS" with
[MENU] key.
1. Receive a half color bar signal in the
TV mode so that the top left zone
should turn white 75% as shown be-
low. Other signal can be fed instead
of the half color bar signal, however,
if the point at the vertical 180th line
and horizontal 46th pixel is of white
75%. (Make the adjustment based on
the setting of this point.)
2. Adjust the "NTSC TAMP" setting on
page 2 of adjustment process mode
so that the "Y" reading on the same
page should be BB - CA.
3. Make the same setting for the PAL-M
TAMP and PAL-N TAMP data.
1. Receive the monoscope pattern sig-
nal.
2. Adjust the "RCUTOFF"
"BCUTOFF" settings on page 2 of
adjustment process mode to achieve
an optimum white balance.
Go to the adjustment mode and
check the following settings.
V176 130
V21 45
13
Adjusting method
1. Adjust the "B+ Adj" value to
5.0 ±0.02V with R3760. Make exact
adjustment of the 5.00 V level
because it will be the reference for
all the other supply voltages. Be sure
to make this adjustment together
with the main PWB (digital PWB).
During the adjustment, be also
careful not to allow the voltage at pin
(2) of P3702 to go above 5.3 V.
1. Select "INCH SIZE" and adjust to
"20" with [VOL+] or [VOL-] key.
* The color of "INCH SIZE" must be
yellow.
1. Adjust "COM BIAS" to the darkest
screen with [VOL+] and [VOL-] key.
* The color of "COM BIAS" must be
yellow.
White 75% at Vertical 180th line and
top left zone horizontal 46th pixel
640 pixels
Page 2 of adjustment process mode
2
> COM BIAS
NTSCTAMP
PAL-M TAMP
PAL-N TAMP
RCUTOFF
GCUTOFF
BCUTOFF
G3 B3 R3 00 00
G1 B4 Y EF C7
TAMP H
TAMP L
GAIBU VER0.000
1. Do not change the "GCUTOFF" setting
because otherwise the black level may
and fluctuate.
See if all the settings are as speci-
fied. If not, select an item in question
with [VOL+] or [VOL-] key and adjust
the setting as shown at left.
* An item selected will be highlighted
in yellow.
LC-20B2UA
480 lines
90
20
20
20
-1
0
-1
00
C2
CA
BB
"Y" data
(white 75%)