Pioneer SX-950 Reference guide

SX-950 ALIGNMENT PROCEDURES
9.1 AM SECTION
1. Set function switch to AM.
2. Connect AM signal generator through 1k-ohm
resistor to AM antenna terminal.
3. Set DUPLICATE switch to OFF and connect
an AC voltmeter to TAPE 1 REC jacks.
4. Set AM SG for 400Hz 30% modulation 100dB
output.
5. Set SX-950 dial indication and AM SG
frequency for 600kHz.
6. Adjust T8 core for maximum reading on AC
voltmeter.
7. Set SX-950 dial indication and AM SG
frequency for 1,400kHz.
8. Adjust TC5 for maximum reading on AC
voltmeter.
9. Set AM SG for 30dB output.
10. Set SX-950 dial indication and AM SG
frequency for 600kHz.
11. Adjust T7, T8 and bar antenna core for
maximum reading on AC voltmeter.
12. Set SX-950 dial indication and AM SG
frequency for 1,400kHz.
13. Adjust TC5, TC6 and TC7 for maximum
reading on AC voltmeter.
14. Repeat steps 10-13 to eliminate variations in
AC voltmeter readings.

9.2 FM TUNER
1. Set function switch to FM.
2. Set FM MUTING switch to OFF.
3. Connect FM signal generator through 300-ohm
dummy load to 300 ohm FM antenna terminals.
4. Set DUPLICATE switch to OFF and connect
AC voltmeter to TAPE 1 REC jacks.
5. Set FM SG for 100dB output at 400Hz and
100% modulation.
6. Set SX-950 dial indication and FM SG
frequency for 87.4MHz.
7. Adjust T4 core for maximum indication on
SIGNAL meter.
8. Adjust T6 lower core for center of scale
indication on TUNING meter.
9. Set FM SG for 8dB output and adjust cores of
T1, T2, and T3 for maximum reading on AC
voltmeter.
10. Set FM SG for 100dB output.
11. Set SX-950 dial indication and FM SG
frequency for 106MHz.
12. Adjust TC4 for maximum indication on
SIGNAL meter.
13. Set FM SG for 8dB output and adjust TC1,
TC2 and TC3 for maximum reading on AC
voltmeter.
14. Set FM SG for 100dB output.
15. Set SX-950 dial indication and FM SG
frequency for 87.4MHz.
16. Adjust T4 core for maximum indication on
SIGNAL meter.
17. Set FM SG for 8dB output and adjust cores of
T1, T2 and T3 for maximum reading on AC
voltmeter.
18. Repeat steps 10-17 to eliminate variations in
AC voltmeter readings.
19. After completing above adjustments, adjust T5
core for maximum reading on AC voltmeter.
20. Detune SX-950 to where only noise is
received and adjust T6 lower core for center of
scale indication on TUNING meter.
21. Set FM SG for 98MHz 60dB output.
22. Tune SX-950 for exact center of scale
indication on TUNING meter.
23. Adjust T6 upper core for minimum distortion.
24. Repeat steps 20- 23 to eliminate variations in
point of minimum distortion.
25. Set FM SG for 100dB output and adjust VR3
so that SIGNAL meter indicates 5 of the scale.
Multiplex Decoder
26. Connect MPX SG (multiplex signal generator)
to the external modulator terminals of the FM
SG and set the FM SG for external
modulation.
27. Connect PILOT OUT terminal of MPX SG to
horizontal input terminal of oscilloscope.
28. Through probe, connect oscilloscope vertical
input terminal to terminal No. 19.
29. Set FM SG for 98MHz 60dB output
unmodulated.
30. Tune SX-950 for exact center of scale
indication on TUNING meter.
31. Adjust VR1 so that 4:1 frequency ratio
Lissajous' (see note below) figure becomes
stationary.
32. Set FM SG for 1kHz (L or R), ?67.5kHz
deviation, 19kHz (pilot signal) and +7.5kHz
modulation.
33. Adjust VR2 for minimum L-R crosstalk.
Note:
Signal at terminal No. 19 is 76kHz sawtooth wave
and MPX SG pilot out is a 19kHz sine wave.
These form a Lissajous figure as shown in Fig.
23.

FM Alignment
If FM stations have drifted in their indicated positions on the dial you might be able to get the FM
Local Oscillator back to where it belongs with a bit of luck and careful adjustment.
Set the SX-950 tuning pointer to about 98 MHz, at the indicated frequency of a known station very
close to 98. Then get another FM receiver tuned to this station to hear the audio content. Verify that
the movable fins of the SX-950 tuning variable capacitor are at their approximate midpoint as well.
This is critical.
Attempt to adjust TC4to locate and tune the known station. Basically you are going to walk the tuning
to the correct indicated position. This adjustment will be extremely sensitive. Ideally a plastic tool
with a metal blade would be used to trim this adjustment (such as a trimpot tool) but a micro
screwdriver may suffice. Be aware the metal screwdriver shaft can affect the capacitance or
inductance of the device being adjusted. Anticipate this factor to get it close once the tool is moved
away from the device.
IF YOU GET LOST, stop at a station, then use the other FM receiver to match the audio and read the
frequency.
Alternately, you can also begin with the tuner set to 98MHz, tune TC4to the first audio you can find,
then find the station frequency with the other receiver. Adjust the SX-950 to the next station's audio,
determine where you are at and keep on repeating until the station is located.

9.3 POWER AMPLIFIER SECTION
1. Turn VR3 and VR4 fully counter-clockwise before
turning on the power.
2. Remove jumper plugs connecting POWER IN and PRE
OUT jacks.
3. Connect 5.1 K-ohm resistor to POWER IN jacks.
4. Set power amplifier for no load.
5. Set POWER switch to ON.
6. Adjust VR1 for 0V between terminals No. 10 and No. 9.
7. Adjust VR2 for 0V between terminals No. 25 and No.
24.
8. Adjust VR3 for 20mV between terminals No. 12(+) and
No. 13(-).
9. Adjust VR4 for 20mV between terminals No. 27(+) and
No. 28(-).
10. Allow set to warm up for at least 10 minutes, then
readjust.