Sharp VC-H88GM Serviceanleitung Seite 9

Note:
SYNCTIP
WHITE CLIP LEVEL
Figure 2-4.
From sync tip to white peak,the level is 100%.
The white clip level is 90% above the white level.
(There is no dark clip adjustment.)
ADJUSTMENT OF FM CARRIER FREQUENCY
AND DEVIATION
Frequency counter
Oscilloscope
Record/Playback
EIA colour bar(1.0Vp-p)
TP203(pin 50 of 1C401)
VIDEO OUT jack
R205 FM carrier control
R204 Deviation control
3.8+0.05 MHz
1.0 + 0.04Vp-p
1. Be sure that R202(E-E level)has been correctly
adjusted.
2. Connect a 75 ohm terminating resistor to the
VIDEO OUT jack and connect an oscilloscope
across this resistor.(See Note below.)
3. Connect a frequentcy counter to test points
TP203(Sig.)~TP2203(GND).
4. Put the unit in A/V input mode.
Do not feed any signal to VIDEO IN jack.
(Disconnect any cable from video input
terminal.)
5. Under this condition,adjust R205 so that the
frequency counter reads 3.8MHz.
6. Feed the EIA standard colour bar signal to the
VIDEO IN jack and adjust R204 so that the
frequency counter reads 4.3MHz.
7. Repeat step 5 thru 6 a few times.
8. Under this condition record the EIA colour bar
on tape,rewind and play back.
9. Make sure that the amplitude of the playback
colour bar signal is 1.0+0.04Vp-p as shown in
Figure 2-5.
If it is out of specified value, check the
PLAYBACK LEVEL(R201)and retry this
adjustment.
Measuring
instrument
input signal
Test point
Control
Specification
VC-H88GM
Figure 2-5.
Note:
If the 75 ohm terminating resistor is missing, the
signal amplitude will be doubled.
ADJUSTMENT OF RECORDING CURRENT
Oscilloscope
Standard colour bar
(stair-case waveform)
TP301(GND),TP302(SiG)
(External trigger: Video output
terminal)
Adjusting point | R206(Record Y Level control)
Specification 240 + 10m Vp-p
1. Feed the standard colour bar signal(stair-case
waveform) to the video input terminal.
2. Connect the probe's GND and SiG leads TP301
and TP302, respectively.
3. Turn R206 to minimize the FM luminance
signal.
4. Adjust R206 so that the amplitude of sync tip
portion is 240 + 10m Vp-p shown in Figure 2-6.
5. Remove QCNW-6443GEZZ after adjustment.
(Also remove connecting probe of TP301 and
TP302.)
Measuring
instrument
Input signal
Test point
SOCKET
TP301
PWB
SHIELD CASE
Figure 2-6.