Sharp VC-90ET Service Manual page 38

VC-90ET
Figure 2-13.
Adjustment of delay level
Dual-beam oscilloscope
Playback
Alignment tape (VROCPSV)
(stair-case waveform)
Test point CH-1; TP203 CH-2; TP204
Adjusting point | R234 (delay level control)
Specification CH-2 level = CH-1 level
1. Insert the alignment tape and play it.
2. Adjust R234 (delay level control) so that the
levels of CH-1 and CH-2 are the same as shown
in Figure-2-14.
Figure 2-14.
2.0Vp-p
Measuring
instrument
Tape used
10 psecdiv
Adjustment of the APC (PAL)
[Mode | Playback
Alignment tape (VROCBFFS)
(stair-case waveform)
Adjusting point | C521 (APC control)
4.433619MHz + 20Hz
1. Insert the alignment tape and place the unit to
the playback mode.
2. Connect the frequency counter to TP501.
Adjust C521 (APC control) so that the counter
reading be 4.433619MHz + 20Hz.
Adjustment of the APC (NTSC)
Playback
Tape used Alignment tape (VROCPSV)
(stair-case waveform)
Test point TP501
Adjusting point | C525 (APC control)
Specification 3.579545MHz + 20Hz
1. Insert the alignment tape and place the unit to
the playback mode..
2. Connect the frequency counter to TP501.
Adjust C525 (APC control) so that the counter
reading be 3.579545MHz + 20Hz.
Measuring
instrument
Adjustment of NTSC Skew Compensation
Measuring Oscilloscope
instrument Monitor
|Mode —_—i|_- Playback (SP still mode)
Alignment tape (VROCPSV)
Test point CH-1 : TP2
CH-2 : Video output terminal
Adjusting point | R4411 (Ficker control)
Specification | No flicker on the monitor TV
screen
1.
Insert the alignment tape (VROCPSV) and place
the unit to the playback still mode.
2. Observe the output of TP2 (head switching
pulse) and video output with an oscilloscope.
3. Adjust R4411 so that there is a video level
difference of + 0.1V between Channel-1
output (head switching pulse's High level) and
Channel-2 output (head switching pulse's Low
level).
4. If the colour flicker is so noticeable on the TV
monitor, finely adjust R4411 so that there is the
least deviation of flicker on the screen.