Sencore SG-165 Manual

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SG165 CALIBRATION PROCEDURE
SG165 SETTINGS
Function -400 Hz Sine Wave
Speakerload -Speakers
Power Range -Separation Test
Left and Right -Off
400 Hz
Pilot 19 KHz -0
FM Modulation -IHF MPX
AM Modulation -0
RF Tuning -Fully CCW
Marker Height -Mid-scale
AM/FM IF Rocker -Mid-scale
Microvolt Output -X1000
Microvolt Output
Adjustment -Fully CW
EQUIPMENT NEEDED
Scope -SC61
Frequency Counter -FC71
RF Voltmeter -Boonton
POWER SUPPLY
1. Measure voltage on positive lead of C105.
2. Adjust R113 for a negative voltage of equal value as measured at the negative lead of C106.
400 HZ SINE WAVE
1. Connect scope to “all signal output” of SG165.
2. Adjust R375 for frequency of 400 Hz.
3. Level should be about 30 VPP with direct lead.
4. Switch to 400 Hz square wave.
5. Signal should be of same frequency and amplitude as sine wave.

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SG165 CALIBRATION PROCEDURE
EXTRA CRYSTAL
1. Switch to extra crystal.
2. Output should be nothing unless crystal is in the SG165 crystal holder.
67 KHz
1. Switch to SCA 67 KHz.
2. Adjust L307 for frequency of 67 KHz.
MPX SIGNAL
1. Switch to Max signal.
2. Turn left 400 Hz on. Should see multiplexed 400 Hz sine wave.
3. Turn left 400 Hz off.
4. Turn right 400 Hz on. Should see multiplexed 400 Hz sine wave.
5. Adjust R250 for a straight baseline.
6. Turn left 400 Hz on. Signal should turn into a pure sine wave.
7. Turn pilot 19 Khz to 5%. Sine wave should be modulated with 19 Khz.
8. Turn Pilot 19 Khz to 10%. Sine wave should be modulated more.
9. Switch FM output modulation to STD. MPX. output should decrease in level. Switch FM
output modulation to IHF MPX.
10. Switch left 400 Hz, right 400 Hz, and Pilot Khz off.
10.7 MHz SWEEP AND MARKERS
1. Switch to 10.7 MHz Sweep and Markers.

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2. Connect oscilloscope to bare wire near TR305 and adjust L305 for 100 KHz output on
scope.
SG165 CALIBRATION PROCEDURE
3. Connect Channel A and B scope probes to molex Pins 2 and 3 of 300 board. Push vector
on scope and switch A and B volts per division to same setting, adjust timebase for closest
thing to a circle. Adjust R103 for a perfect circle.
4. Hook all signal output to Channel B on scope. Adjust volts/division for 5. Hook “to scope”
on SG165 to Channel A on scope. Adjust volts/division to 1. Lock pattern in with Time Base
Adjustment. Scope should show a 10.7 MHz sweep with 3 beautiful markers endowing it.
RF LEVELS
1. Switch 10.7 MHz IF.
2. Connect all signals output to RF voltmeter.
3. Adjust R391 for 100 mV.
4. Switch to 10.7 MHz XTAL controlled. Reading should be similar.
5. Switch to AM RF.
6. Adjust R392 for 100 mV.
7. Check X1000 and X10 for levels at all AM dial frequencies.
8. Switch to FM RF.
9. With microvolt output at X1000, adjust R360 for 10 mV.
10. Check X1000 and X100 for all FM frequencies.
11. Switch back to X1000.
FREQUENCY CALIBRATION
1. Switch to AM RF.

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2. Connect all signal output to 1 Meg load on FC71.
3. Set dial for 500 KHz.
SG165 CALIBRATION PROCEDURE
4. Adjust L302 for 500 KHz on FC71.
5. Set dial for 1600 KHz.
6. Adjust C305A for 1600 KHz on FC71.
7. Check 1000 KHz for frequency.
NOTE: One calibration may affect the other somewhat.
8. Switch to 10.7 MHz IF.
9. Adjust AM/FM IF Rocker for mid-scale.
10. Adjust L301 for 10.7 MHz on FC71.
11. Rotate rocker switch. Output should vary to at least 10.45 MHz to 10.95 MHz.
12. Switch to 10.7 MHz XTAL controlled. Frequency should read 10.7 MHz.
13. Switch to 455 KHz IF.
14. Connect all signals output to SC61.
15. With rocker at mid-scale, adjust L303 for 455 KHz.
16. Swing rocker back and forth. Frequencies should adjust.
17. Switch to 262 KHz IF.
18. With rocker at mid-scale, adjust L304 for 262 KHz.
19. Swing rocker back and forth. Frequencies should adjust.

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20. Switch AM modulation switch to 30%. AM should be modulated on scope.
21. Switch to FM RF.
22. Connect all signals out to 50 ohm input on FC71.
23. Set dial for 88 MHz.
SG165 CALIBRATION PROCEDURE
24. Adjust L308 for 88 MHz on FC71.
25. Set dial at 108 MHz.
26. Adjust C341A for 108 MHz on FC71.
27. Check frequency at 98 MHz.
NOTE: One calibration may affect the other somewhat.
METER LOAD TEST
1. Hook all signal output to radio test through 39G43 red and black leads.
2. Turn 19 KHz pilot to 10%.
3. Turn SG165 dial until the frequency is similar to the radio’s frequency.
4. Adjust dial until pilot light comes on in the radio.
5. Turn left 400 Hz on. Left meter should peg right.
6. Turn right 400 Hz. Right meter should peg right.
7. Turn power range to 10w. Readings should decrease by a factor of 10. Turn power range
to 100w, readings should decrease by a factor of 10 again. Turn power range to separation test.
8. Turn left 400 Hz off. Left meter should go down and right meter should still peg right. Turn
left 400 Hz off.

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9. Switch pilot 19 KHz to 5%. Pilot light should remain on. Switch pilot 19 KHz to 0 and
pilot light should disappear.
10. End of test.