Sharp 29MR70, Service Manual

Page: 9 / 36

9
29MR70
Figure B: WAVEFORM FOR SCREEN ADJUSTMENT
SERVICE ADJUSTMENT
Note: Before making the service adjustment, make the
bus data settings.
+B Adjustment
(1) For the chassis with the +B adjustment control
1. Receive a good local channel.
2. Select VIDEO ADJUSTMENT RESET on the
menu to get the video reset.
3. Connect a DC voltmeter between the +B line (at
SW transformer) of R611 and the ground terminal.
4. Adjust R738 so that the voltmeter should read
128.5+0.5V/-0.25V.
(2) For the chassis without the +B adjustment
control
1. Receive a good local channel.
2. Select VIDEO ADJUSTMENT RESET on the
menu to get the video reset.
3. Connect a DC voltmeter between the +B line (at
SW transformer) of R611 and the ground terminal.
4. Make sure that the voltmeter reads 128.5±1.5V.
Video Level (TV Det Video Level)
Adjustment
1. Receive a good local channel.
2. Enter the service mode signal category and select
the service adjustment "S02".
3. Set the data value to "02" first, then adjust the data
to "04". (If out of spec, readjust the data in the range
of "00" to "07" to obtain a normal contrast level.)
RF AGC Adjustment
1. Receive a good local channel.
2. Enter the service mode signal category and select
the service adjustment "S01".
3. Set the data value to point where no noise or beat
appears.
4. Select another channel to confirm that no noise or
beat appears.
Note: You have to exit the service mode first to
select another channel.
Screen Adjustment
1. Connect to oscilloscope probe between TP854 and
ground of the CRT unit.
2. Receive a good local channel.
3. Enter the service mode Signal category and set the
service adjustment "S04" to step 30. Then select the
service adjustment "S12" and set the data value to
"00" to set the color level to the minimum level. (record
the original data first). You may skip this step, if you
selected a B/W picture or monoscope pattern. Set
also the "S05/S06/S07" data to minimum level ("00").
2.35 Vdc
GND
4. Select the service adjustment "S03" and set the data
value to "01" to turn off the luminance signal (Y-mute).
5. Select the service adjustment "S13" and adjust the
data value to obtain 2.35 volts as shown in Figure B .
6. Adjust the master screen control until the raster
darkens to the point where raster is barely seen.
7. Adjust the service adjustment "S05" red, "S06" green,
"S07" blue to obtain a good grey scale with normal
white at low brightness level.
8. Select the service a adjustment "S03" and reset data
to "00". Select the service adjustment "S12" and reset
data to obtain normal color level.
9. Remove probe and reset the master screen control
to obtain normal brightness range.
White Balance Adjustment
1. Receive a good local channel.
2. Select the service adjustment "S12" and set the data
value to "00" to set the color level to the minimun.
You may skip this step, if you selected a B/W picture
or monoscope.
3. Alternately adjust the service adjustment data of "S08"
and "S09" until a good grey scale with normal white
is obtained.
4. Select the service adjustment "S12" and reset data
to obtain normal color level.
Sub-Picture Adjustment
1. Receive a good local channel.
2. Make sure the customer picture control is set to
maximum.
3. Enter the service mode and select the service
adjustment "S10".
4. Adjust the data value to achieve normal contrast
range.
Sub-Tint Adjustment
1. Receive a good local channel.
2. Set the customer tint control to the center of it’ s range.
3. Enter the service mode and select the service
adjustment "S11".
4. Adjust "S11" data value to obtain normal fresh tones.
Sub-Color Adjustment
1. Receive a good local channel.
2. Make sure the customer color control is set to center
position.
3. Enter the service mode and select the service
adjustment "S12".
4. Adjust "S12" data value to obtain normal color level.
Sub-Brightness Adjustment
1. Receive a good local channel.
2. Make sure the customer brightness control is set to
center position.
3. Enter the service mode and select the service
adjustment "S13".
4. Adjust "S13" data value to obtain normal brightness
level.