Panasonic CT-32HX40CB, Руководство по обслуживанию

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Service Adjustments (Electronic Controls, cont.)
MTS Circuit Adjustments
The MTS Circuit Adjustments require two steps:
1.
Input Level Adjustment.
2. Stereo Separation Adjustment.
Input Level Adjustment
Serviceman DAC Adjustment (MTSIN)
Preparation:
1.
Connect an RMS meter with filter jig as shown in
Fig. 42.
2. Connect an RF signal generator to the RF
antenna input.
Procedure:
1.
Apply the following signal from the RF signal
generator:
Video: 100 IRE flat field, 30% modulation.
Audio: 300Hz, 100% modulation, monaural
(70 ±5dB, 75
Ω
OPEN, P/S 10dB). Make sure that
the 75
µ
s pre-emphasis is OFF.
2. Adjust the MTS Input Level Adjustment (MTSIN)
data until the RMS voltage measured is
490 ± 20mVrms.
Stereo Separation Adjustment (SEPAH)
Preparation:
1. Connect an RF signal generator to the RF
antenna input.
2. Connect a scope to TPA19.
Procedure:
1.
Select Stereo Mode in Audio menu
2. Apply the following signal from the RF signal
generator:
Video: 100 IRE flat field, 30% modulation.
Audio: 300Hz, 30% modulation, stereo (left only)
(70±5dB, 75
Ω
OPEN, P/S 10dB).
Note: After setting 30% modulation with P.L.
SW and N.R. SW OFF, turn P.L. SW
and N.R. SW ON.
3. In Serviceman Mode, Adjust the MTS Low-Level
Separation Adjustment (SEPAL) data until the
amplitude displayed on the scope is minimum.
4. Apply the following signal from the RF
signal generator:
Video: 100 IRE flat field, 30% modulation.
Audio: 3KHz, 30% modulation, stereo (left only)
(70 ±5dB, 75
Ω
OPEN, P/S 10dB).
Note: After setting 30% modulation with P.L.
SW and N.R. SW OFF, turn P.L. SW
and N.R. SW ON.
5. Adjust the MTS High-level Separation Adjustment
(SEPAH) until the amplitude displayed on the
scope is minimum.
6. Repeat above steps 2 through 4 until the amplitude
is at minimum for both signals.
10k
4700p
Figure 42. Filter Jig
TPA20
RMS
METER