15.10 MTS circuit adjustmens

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The MTS circuit adjustments require two steps:

1. Input level adjustment.

2. Stereo separation adjustment.

Input level adjustment
Service DAC adjustment (MTSIN)

PREPARATION

1. Connect an RMS meter with filter jig as shown in figure to TPA19 (L_OUT)

   

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, 75Ω OPEN, P/S 10dB). Make sure that the 75μs pre-emphasis is OFF.

2. Adjust the MTS input level adjustment “MTSIN” data until the RMS voltage measured is 106 ± 6.0mVrms.

Stereo separation adjustment (SEPAH)

PREPARATION

1. Connect an R.F. signal generator to the RF antenna input.

2. Connect a scope to TPA20.

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, 75Ω 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 service 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, 75Ω 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 5 until the amplitude is at minimum for both signals.

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