Service manual

14
LC-20B4U-S
LC-20B4U-B
4. Adjustments
1 B+ Adjustment
(R3714)
2 Inch Size setup
(If E
2
PROM is replaced)
(IC2010)
3 Common-bias adjustment
4 TAMP adjustment
Adjustment Adjusting conditions Adjusting method
1. Connect the DC voltmeter to
pin (4) of P3701.
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 187 - 202.
3. Make the same setting for the PAL-
M TAMP and PAL-N TAMP data.
1. Adjust the "B+ Adj" value to
5.0±0.02V with R3714. Make exact
adjustment of the 5.00V 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
P3701 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
top left zone
Vertical 180th line and
horizontal 46th pixel
480 lines
640 pixels
On usual screen ("Y" data is not exact.)
2
COM BIAS 118
TAMP L 187
TDATA –
TAMP H 202
NTSC TAMP 20
PAL-M TAMP 20
PAL-N TAMP 20
2
NTSC TAMP 20
YDATA 187 *** 202
↑
On single-item screen ("Y" data is exact.)
↑
"Y" data
"Y" data