
Model 8640B
TM 9-4935-601-14-7&P
ADJUSTMENTS
5-42. RF OSCILLATOR END STOP ADJUSTMENT (Cont'd)
Figure 5-11. Location of RF Oscillator Stop Adjustments.
Shown in Maximum ccw Position. Top View with Instrument Upside Down.
10. Recheck high stop frequency and repeat preceding step as needed until stop frequency is correct. Then secure
both setscrews.
NOTE
If the preceding steps have no effect, check that the VT and FM Gain Compensation pots do not
reach their stops first. If so, loosen the gear on the pot shaft and continue.
11. Adjust FREQUENCY TUNE fully ccw. The frequency should read between 0.4475 and 0.4482 MHz. If it does
not, note how far off the frequency is.
12. Adjust FREQUENCY TUNE cw until first setscrew on adjustable stop ring appears. Loosen setscrew.
13. Tune further cw until second setscrew appears.
14. Loosen setscrew and rotate FREQUENCY TUNE up or down by the amount of correction needed (as noted in
step 11), and tighten setscrew. Do not allow adjustable stop ring to rotate.
15. Recheck low stop frequency and repeat preceding step as needed until stop frequency is correct. Then secure
both setscrews.
CAUTION
Do not overtighten setscrews. This may crack the adjustable end stop.
NOTE
If the preceding steps have no effect, check that the VT and FM Gain Compensation pots do not
reach their stops first. If so, loosen the gear on the pot shaft and continue.
5-37
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