Sharp LC-20B1U Service Manual page 14

LC-20B1U
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
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. A d j u s t t h e " R C U TO F F " a n d
"BCUTOFF" settings on page 2 of
adjustment process mode to achieve
an optimum white balance.
14
Adjusting method
1. Adjust the "B+ Adj" value to
5.0 ±0.02V with R3760. Make exact
adjustment of the 5.00 V level be-
cause 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
90
NTSCTAMP 20
PAL-M TAMP 20
PAL-N TAMP 20
RCUTOFF -1
GCUTOFF 0
BCUTOFF -1
G3 B3 R3 00 00 00
G1 B4 Y EF C7 C2
TAMP H CA
TAMP L BB
GAIBU VER0.000
1. Do not change the "GCUTOFF" setting
because otherwise the black level may
fluctuate.
480 lines
"Y" data
(white 75%)