Demodulation Circuit Adjustment - Sony HXC-100 Service Manual

3-8-2. Demodulation Circuit Adjustment

Preparations
. Supply the DC IN connector with external power (+12 V).
. Set the CAMERA POWER switch to EXT.
. Disconnect the coaxial cable from the connector CN601 on the TX-126 board, and connect the FM signal generator to
CN601.
Input the following FM signal.
Carrier: 1.0 MHz, AF: 1 kHz, Dev: ?3 kHz, RF level: _15 dBm
Tuning Adjustment
1. Connect the oscilloscope to the following terminals on the TX-126 board.
Test Point: TP4 (B-2)
GND: E301 (D-1)
2. Adjust the LV2 (B-3) on the TX-126 board so that the DC level becomes 6.3 ?0.5 V.
3. Connect the audio analyzer to the following terminals on the TX-126 board.
Test Point: TP2 (A-3)
GND: E2 (A-2)
Audio analyzer:
Unbalanced, high-impedance, HPF: 400 Hz, LPF 20 kHz
4. Measure the distortion with the audio analyzer and adjust the LV3 (B-3) on the TX-126 board so that the distortion
becomes minimum.
5. Fine-adjust the LV2 (B-2) on the TX-126 board so that the waveform distortion becomes minimum.
6. Repeat steps 4 and 5 to minimize the distortion.
7. Check that the DC level of terminal TP4 on the TX-126 board is 6.3 ?1.5 V with the oscilloscope.
8. Check that the distortion is 0.40% or less with the audio analyzer.
Output Level Adjustment
1. Connect the oscilloscope to the following terminals on the TX-126 board.
Test Point: TP2 (A-3)
GND: E2 (A-2)
2. Adjust the RV2 (A-3) on the TX-126 board so that the waveform level becomes 220 ?10 mVp-p.
HXC-100/V1 (E)
A = B
A
B
6.3 ? 0.5 V
GND
3-35