Sharp VC-H92HM Serviceanleitung Seite 42

Y/C CIRCUIT ADJUSTMENT
CHECKING OF VIDEO E-E LEVEL
Oscilloscope
1. Connect a 75 ohm terminating resistor to the
VIDEO OUT jack and connect an oscilloscope
across this terminating resistor.
(See Note below.)
Measuring
instrument
Input signal
Test point
Specification
2. Feed a colour bar signal to the VIDEO IN jack.
3. Make sure that the E-E signal amplitude is 1.0
Vp-p as shown in Figure 5-3.
Figure 5-3.
Note:
If the 75 ohm terminating resistor is missing, the
signal amplitude will be doubled.
CHECKING OF WHITE CLIP LEVEL
Oscilloscope
1. Connect a oscilloscope to Pin (48) of IC401 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
isclipped at 190% as shown in Figure 5-4.
SYNCTIP
Measuring
instrument
Input signal
Test point
Specification
WHITE CLIP LEVEL
Figure 5-4.
4
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
Oscilloscope
EIA colour bar (1.0Vp-p)
TP301 (Sig) ~ TP302 (GND)
SP mode
Chroma (Red) :50+4mVp-p
: 185 +30mVp-p
Specifications
Chroma (Red)
Sync tip
: 40 + 3mVp-p
: 160 +20mVp-p
1. Feed the colour bar signal to the VIDEO IN jack
and set the unit in recording mode.
2. Connect an oscilloscope to shown in table.
3. Make a short-circuit both ends of L209 with a
A7F/16V capacitor, and minimize the FM
luminance signal.
4. Make sure so that the amplitude of the chroma
(red) portion is specified as shown in Figure 5-
5(a).
5. Disconnect the capacitor that was connected in
step 3.
6. Make sure so that the amplitude of the sync tip
portion is specificed as shown in Figure5-5(b).
Red
Figure 5-5(a).
Figure 5-Sib).