Service Adjustment; White Balance Adjustment; Vco Adjustment; Rf Agc Adjustment - Sharp 25VT-J100 Service Manual

SERVICE ADJUSTMENT

VCO Adjustment

1. Connect a digital voltmeter between pin(44) of IC401
and ground.
2. Select a good local channel.
3. Enter the service mode. select adjustment "PIF-
VCO" and data value "64".
4. Adjust the VCO coil T201 so that the digital voltmeter
reads 2.5 volts.
5. Adjustment is complete, remove the voltmeter,
return to "normal" mode.

RF AGC Adjustment

1. Have unit receive a good local channel.
2. Enter the service mode and select service
adjustment "RF-AGC".
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 1: You will have to come out of the service
mode to select another channel.
Note 2: Setting the data to "0" will produce a
black raster.

Screen adjustment

1. Select a good local channel.
2. Enter the service mode and select service
adjustment "COLOR" and set the data value to "0"
to set the color level to minimum.You may skip this
step if you selected a B/W picture or monoscope
pattern.
3. Select service adjustment "MUTE" and adjust the
data value to "1" this turns off the luminance signal
(Y-mute) .
4. Select service adjustment "BRIGHT" and adjust data
value to "28".
5. Adjust the master screen control untill raster darkens
to the point where raster is barely seen.
6. Adjust service adjustments "R-CUT OFF" red,"G-
CUT OFF" green and "B-CUT OFF" blue to obtain
a good grey scale with normal whites at low
brightness level.
7. Select service adjustment "MUTE" and reset data
to" 0" Select service adjustment "COLOR" and reset
data to obtain normal color level.
8. Remove digital voltmeter. reset master screen
control to obtain normal brightness range.

White balance adjustment

1. Have unit receive a good local channel.
2. Enter the service mode. select service adjustment
"COLOR" and set to "0" ( minimum color) . "COLOR"
does not have to be adjusted if you selected a B/W
picture or monoscope pattern.
3. Alternately adjust service adjustment data of "G
GAIN" and "B GAIN" untill a good grey scale with
normal whites is obtained.
4. Select service adjustment "COLOR"and adjust data
to obtain normal color level.
Sub-picture adjustment
1. Have unit receive a good local channel.
2. Make sure the customer picture control is set to
maximum.
3. Enter the service mode and select service
adjustment "PICTURE".
4. Adjust the data value to achieve normal contrast
range.
Sub-Tint Adjustment
1. Have unit receive a good local channel.
2. Set customer tint control to center of it's range.
3. Enter the service mode and select service
adjustment "TINT".
4. Adjust "TINT" data value to obtain normal flesh tones.
Sub-color adjustment
1. Have unit receive a good local channel.
2. Make sure the customer color control is set to
center position .
3. Enter the service mode and select service
adjustment "COLOR".
4. Adjust "COLOR"data value to obtain normal color
level.
Sub-brightness adjustment
1. Have unit receive a good local channel.
2. Make sure the customer brightness control is set to
center position.
3. Enter the service mode and select service
adjustment "BRIGHT".
4. Adjust "BRIGHT"data value to obtain normal
brightness level.
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25VT-J100
25VT-CJ10