Sharp VC-MH80 Service Manual page 39

CHECKING OF VIDEO E-E LEVEL
Input signal
VIDEO OUT jack
Test point
Connect a 75 ohm terminating resistor to the
1 i .
VIDEO OUT jack and connect an oscilloscope
across this terminating resistor.
(See Note below.)
2. Feed a colour bar signal to the VIDEO IN jack.
3. Make sure that the E-E signal amplitude is 1.0
Note:
If the 75 ohm terminating resistor is missing, the
signal amplitude will be doubled.
CHECKING OF WHITE CLIP LEVEL
Measuring Oscilloscope
instrument
E-E or Record
Mode
Input signal
Test point Pin (48) of IC201, GND
Specification 190 f 5% (See note below)
1. Connect a oscilloscope to Pin (48) of IC201 and
GND.
2. Feed the colour bar signal to the VIDEO IN jack
and set the unit in E-E or recording mode.
3. Make sure that the overshoot of the video signal
. . . . . . . . . . . . . . .
Note:
From sync tip to white peak, the level is 100%.
The white clip level is 90% above the white level.
CHECKING OF RECORD LEVEL
Measuring
instrument
I
Record mode (PAL LP mode)
Mode
Record mode (SECAM LP mode)
Input signal PAL colour bar signal (1 .OVp-p)
SECAM colour bar signal
(VC-MH80 ONLY)
Control I R224 (REC-Y LEVEL)
Chroma (Red) : 44 5 8mVp-p
Chroma (Cyan) : 44 + 8mVp-p
(VC-MH80 ONLY)
Sync tip: 140 i 1 SmVp-p
1. Feed the PAL colour bar signal to the VIDEO IN
jack and set the unit in recording mode.
Connect the oscilloscope to test points TP301
2.
(Sig.) and TP302 (GND).
Set the unit in the LP recording mode.
3.
Turn R224 (REC-Y LEVEL) to minimize the FM
4.
luminance signal.
5. Make sure so that the amplitude of the chroma
(red) portion is specified as shown in Figure 5-6
In the next place put the unit in SECAM mode
6.
with the feed the SECAM colour bar signal to the
VIDEO IN jack and set the unit in recording
mode. (VC-MH80 ONLY)
Make sure so that the amplitude of the chroma
7.
(cyan) portion is specified as shown in Figure 5-6
Again feed the PAL colour bar signal to the
8.
VIDEO IN jack and set the unit in recording
mode.
Adjust R224 (REC-Y LEVEL) so that the amplitude
9.
of sync tip portion is specified as shown in Figure
39
VC-MH80
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