Pioneer SX-3700 Service Manual page 18

Multiplex Decorder
* Connect the MPX SG (FM multiplex generator)
to the external modulator terminals of FM SG,
thereby using FM SG as extemal modulation.
1. Set the FM SG output frequency to 98MHz,
output level to 60dB (unmodulated), and tune
the SX-3700 to this frequency.
2. Adjust the VR1 to obtain a 7 6kHz signal at
No. 7 terminal (AWV-011, 36 Pin) on the tuner
assembly.
3. Set the MPX SG modulation output to pilot
signal (19kHz) only, and set the FM deviation
of 7.5kHz (107o modulation).
4. Adjust the VR2 to obtain minimum leakage
of the 19kHz pilot signal at the REC terminal.
5. Raise the FM SG output level to 80dB, and
set the MPX SG to Main lkHz (L+R), 67JckHz
deviation (907o modulation), and pilot signal
to 7 .5kHz deviation (10% modulation).
6. Adjust the T1 core to within 190" to obtain
minimum distortion in the demodulated output
(REC terminal).
sx-37C'C'
8 . 2 A M T U N E R
.
Connect the AM SG (AM signal generator)
to the AM antenna terminal via a 1kO resistor.
o
Set the FUNCTION switch to AM.
1. Tune the SX-3700's dial pointer to 600kHz,
and the AM SG output to 600kHz, 100dB
(modulation -40OHz, 3O% ).
2. Adjust the core of T101 to obtain maximun
output level (REC terminal).
3. Then tune to 1400kH2, and set the AM SG
output frequency to 1400kHz also.
4. This time adjust TC5 to obtain maximum
output level (REC terminal).
5. Repeat steps 1 to 4 above.
6. Set the AM SG output level to 30dB, adjust
the antenna coil along the bar-antenna and
TC4 and TC5 at 1400kHz in the same manner
as described in the above steps. This is the
adjustment
for
optimum sensitivity across
the frequency band, and minimum difference
in sensitivity at different frequencies.
AC voltmeter
antenna coil
T o R E C t e r m i n a l
Fig. 8-3 Adjustment point
Oscilloscope
AM signal generator