Mpx Adjusrment - Pioneer SX-750 Service Manual

6.3 MPX Adjustment
1. Oonnect measuring equipment as shown in
F i g . 1 6 .
2. T\rne FM SG and SX-750 to dial readings of
98MHz.
3. Set FM SG for 60dB unmodulated output.
4. Connect the output signal (19kHz) of MPX SG
PILOT OUT terminal to the horizontal input of
an oscilloscope, and pin 20 of the tuner assembly
(AWE-073) via a probe to the oscilloscope
vertical input.
5. Adjust VR2 so that lissajous pattern displayed
on oscilloscope becomes stationary (Fig. 16).
6. Set MPX SG to 67.5kHz deviation at lkHz for
left and right channels, and to 7 .1kHz deviation
for 19kHz pilot signal.
7. Adjust T5 core for minimurn audio frequency
distortion. Take care to turn core only within
t 1 8 0 ' .
8. Adju.st VR3 for minimum signal leakage from R
channel to L channel, and from L channel to
R channel.
OscilloscoPe
Lissajous
AC voltmeter Distortion meter
" [ E m , / |
1 V
F i s . 1 6