Hallicrafters SX-117, Repair Manual

Page: 17 / 51

17
5-3, MAIN CRYSTAL OSCILLATOR TEST
Each of the crystals in the oscillator has an adjustment. This adjustment affects both the
amplitude and the frequency of the oscillator output.
1, With the controls set per paragraph 5, and the equipment warmed up, connect a cable
from the scope to J4 (CRYSTAL OSC OUTPUT). Adjust L10B for max peak to peak voltage. Record
the peak to peak voltage. Move the cable from the scope to the frequency counter. Readjust
L10B for 10.000MHZ. Move the probe back to the scope observe the signal. If you have not lost
more than 10% of the peak to peak voltage that setting is good. Minimum signal level is 1.0 vpp.
NOTE: Arbitration of signal amplitude and frequency for each crystal in this oscillator may be required. If possible, go with the most accurate
frequency rather than peak output voltage. The CAL RESET function of the VFO can offset up to +/-
1500Hz. Ideally you would adjust for exact
frequency. But unless you have a lot of spare xtals this is impractical.
2, If the WWV xtal is installed turn the BAND SELECTOR to the WWV position repeat the
process in step 1 above adjusting L14.
3, Set the band switch to 7.0 and repeat the process in step 1 above adjusting L11B.
4, Set the band switch to 14.0 and repeat the process in step 1 above adjusting L13B.
5, Set the band switch to 21.0 and repeat the process in step 1 above adjusting L12B.
6, If xtal is installed set the band switch to 28.0 and repeat the process in step 1 above
adjusting L10A.
7, Set the band switch to 28.5 and repeat the process in step 1 above adjusting L11A.
8, If the xtal is installed set the band switch to 29.0 and repeat the process in step 1
above adjusting L12A.
9, If the xtal is installed set the band switch to 29.5 and repeat the process in step 1
above adjusting L13A.
5-3-1, MAIN OSCILLATOR SCHEMATIC & VOLTAGE CHART
PIN # 1 2 3 4 5 6 7 8 9
VOLTAGE 170 0 1.3 6.3vac 6.3vac 170 0 1.0 0
ALL VOLTAGES ARE DC UNLESS OTHERWISE NOTED. You will need an RF blocking probe.