Read Sharp 21KF-80 (serv.man5) Service Manual online
9
21KF-80H
Screen adjustment
1. G2 Adjustment
1.
Enter the service mode (see page 6).
2.
Use the channel up or channel down buttons to enter the << BLUE-BACK >>
function.
3.
Set this to << BLUE-BACK: 0 >>, i.e. blue background is turned off.
4.
Turn the set off at the mains.
5.
Turn the set back on.
6.
Set the picture control settings to normal.
7.
Select the SCART input by pressing the TV/SCART button on the remote con-
trol. Do not connect an input to the SCART socket. A blank raster will appear.
trol. Do not connect an input to the SCART socket. A blank raster will appear.
8.
Connect an oscilloscope to TP851 on the CRT PWB. The waveform as in fig-
ure 4 should be displayed.
9.
Adjust the G2 control (screen voltage) so that the peak of this waveform is 3.5V
+/-0.1V above the zero volt line.
10. Enter the service mode.
11. Turn the blue background function back on again - set << BLUE-BACK: 1 >>.
12. Turn off the receiver using the mains button.
13. The G2 adjustment is now complete.
2. Focus Adjustment
1.
Receive a monoscope pattern signal at a level of 60 to 80 dB
µV.
2.
Set the picture settings to normal.
3.
Adjust the focus potentiometer to obtain maximum definition.
AGC Adjustment
1.
Tune the receiver into a colour bar signal on channel I-42.
2.
Set the RF generator to an output signal strength of 59 dB/
µV (+/-1dBµV) –75 Ohms.
3.
Connect an oscilloscope to TP201. TP201 is one end of R201.
4.
Enter the service mode (see page 6).
5.
Use the channel up and channel down buttons to enter the AGC mode.
6.
By using the volume up and the volume down buttons, adjust the AGC until the voltage on TP201 drops by 0.1V
to 0.3V below its maximum value.
to 0.3V below its maximum value.
7.
Change the input signal strength to 66-70dB
µV and make sure that there is no noise apparent in the picture.
8.
Turn the receiver off at the mains, this will exit the service mode and store the adjustment.
5
Figure 4
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