Panasonic TC20LA5 - 20" LCD COLOR TV, Service Manual

Page: 14 / 40

7.3. MTS Adjustment
Caution:
MTS adjustment shall be after the aging of 30 minutes or longer.
7.3.1. RF Audio Input level Adjustment
Instrument name Connection Remarks
1. Filter jig
2. RF signal generator
3. RMS voltage meter TP3572 - GND
RF ANT. INPUT
Filter jig
Filter jig
1. Apply following RF signal at Antenna input.
VIDEO : Flat field, 30 % modulation
AUDIO : 300 Hz, 100 % modulation, monaural
(70 dB ± 5 dB, 75
W
, P/S 10 dB)
Note:
Make sure 75 us PRE-EMPHASIS is off.
2. Adjust "MTSIN" data (Input level) until the RMS voltage meter indicates 106 mVrms ± 6 mVrms.
7.3.2. Stereo Separation Adjustment
Instrument name Connection Remarks
1. RF signal generator
2. Oscilloscope
3. Headphone jig RF ANT. INPUT
TP3571 - GND
Headphone jig
1. Select STEREO mode in the AUDIO Menu.
2. Set “Audio volume” DAC to “40”.
3. Apply following RF signal at Antenna input.
VIDEO : Flat field, 30% modulation
AUDIO : 300Hz, 30% modulation, STEREO (LEFT only)
(70dB ± 5dB, 75
W OPEN, P/S 10dB)
Note:
After setting 30% modulation with PL SW and NR SW off, turn PL SW and NR SW on.
4. Adjust "SEPAL" data (Low-level separation) until the amplitude.
5. Apply following RF signal at Antenna input.
VIDEO : Flat field, 30% modulation
AUDIO : 3kHz, 30% modulation, STEREO (LEFT only)
(70dB ± 5dB, 75
W
OPEN, P/S 10dB)
Note:
After setting 30% modulation with PL SW and NR SW off, turn PL SW and NR SW on.
6. Adjust "SEPAH" data (High-level separation) until the amplitude of the waveform on the oscilloscope is minimum.
7. Repeat steps 3. to 6. until Low-level separation and High-level separation satisfy above-mentioned conditions.
Note:
The separation must be more than 20 dB at 300Hz and 3kHz.
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TC-20LA5 / TC-20LE5