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5-23-9. INCOM Demodulation Adjustment
Notes :
• This adjustment is necessary only when replacing T202
or T203 on the TR-90 board.
• Use a plastic core driver to adjust 1T.
Equipment
: Oscilloscope Audio generator
Audio analyzer
Preparations :
• INTERCOM level control/rear panel→ 2fully clockwise
• CCU-700/700P/700A/700AP setting
Extend the AT-88 board of the CCU.
S2081 (PGM IN 0 dB/-20 dB)/AT-88 (D-5)→ 0dB
S2082 (PGM MIX ON/OFF)/AT-88 (F-5)→ ON
Test Point
: Pin 4 (X), Pin 3 (G)/
INTERCOM connector
Adjustment Procedures:
1. Feed an 1.0-kHz sine wave signal from the audio
generator to pins D68 (X), A69 (Y), and B69 (GND)
on the extension board (extending AT-88) referring to
Section 5-1-4 "Connection — For audio adjustments".
2. Adjust the audio generator so that the level at TP44
(GND:E1)/AT-88 (L-7) is 200 mVp-p.
3. Connect the oscilloscope to TP204 (GND:E1)/TR-90
(A-3).
4. Slowly turn 1T202 (A-2) until a sign wave appears
around 5.0 Vdc. Adjust 1T202 for the following
specifications.
Adjustment Point : 1T202/TR-90 (A-2)
: C = 5.0 ±0.1 Vdc
Specifications
BVP-500
BVP-500P
5-23. Audio Modulation/Demodulation Adjustment
5-23-9. INCOM Demodulation Adjustment
5. Adjustment Point : 1T203/TR-90 (A-2)
Specifications
: The distortion is 0.3% or less
Resetting after Adjustment:
• S2081, S2082/AT-88 → customer-set position
4
TR
A
TP204
B
C
D
E
F
G
TR-90 BOARD (A SIDE)
and minimum.
3
2
1
T202 T203
E1
5-33
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