Cathode Level Adjustment - Sony VPH-G90U Service Manual

5-3-4. Cathode Level Adjustment

1. Apply the following voltages to CN244 (CN264 and
CN284) of the CDR (CDG and CDB) board:
CN244/CN264/CN284 Pin 1: +175 ± 1 V
CN244/CN264/CN284 Pin 10: +115 ± 0.5 V
2. Connect an oscilloscope to TP1201 on the CBR (CBG
and CBB) board, and adjust RV1223 so that the voltage
becomes 113 ± 0.5 V.
3. Connect an oscilloscope to base terminal of Q948 on
the CDR (CDG and CDB) board, and adjust RV785 on
the CAR (CAG and CAB) board so that the peak
section of the black level becomes 109 ± 0.5 V.
4. Adjust RV718 so that the amplitude of white peak
section becomes 13 ± 0.2 V.
Be sure not to saturate the
white peak section with RV718.
5-4
5-3-5. G1 Level Adjustment
1. Connect an oscilloscope to the plus (+) terminal of
capacitor C820 on the CDR (CDG and CDB) board,
and adjust RV682 so that the black level becomes 12
± 0.2 V.
2. Connect an oscilloscope to TP891 of the CDR (CDG
109 ±0.5 V
and CDB) board, and adjust RV623 so that the white
peak section of the waveform doesn't clip.
13 ±0.2 V
GND
3. Connect an oscilloscope to TP891 on the CDR (CDG
and CDB) board. Make sure that the peak section of the
waveform clips when turn RV622 on the CAR (CAG
and CAB) board counterclockwise. Turn RV622
gradually clockwise and stop it just before the limiter
circuit works.
12 ±0.2 V
Clipping
Approx.10 V
Adjust here
with RV622.
Approx._80 V
VPH-G90E/G90U/G90M
GND
GND