Sect.IV Page 16 Model 618B
-e -&-
15) If satisfactory tracking adjustments still cannot 417A 6180
be made, refer to step 2, Table 4-5. Proper ad-
PRESTO KlDEL 100
justment of pulsing operation assures proper per- YICRQWAVE FRECUENCI
STANDARD
formance in CW and SQ. WAVE. . ,.
16) Set the MOD. SELECTOR to SQ. WAVE and
observe the waveshape across the band. The wave-
shape may be improved by repeating the adjust-
XTAL HARMONIC
ment of R352 and R355 as outlined in step 14 above. GENERAm
I "----
17) Check frequency dial calibration as described
in paragraph 4-13.
Figure 4-12. Test Setup for Fiequency
Calibration
4-13 CALIBRATING THE FREQUENCY DIAL
5) Tune MEGACYCLES dial to 7500. Measure
Replacing the klystron will usually reduce the ac-
output frequency with wavemeter. If output fre-
curacy of the megacycles dial by several percent
quency does not agree with dial within 1%, adjust
from its rated accuracy of 1%. If accuracy of
the frequency dial slightly by slipping it on its shaft.
frequency dial calibration is important, the follow-
ing procedure can be used to restore accuracy.This
6) Check calibration of MEGACYCLES dial through
procedure requires a wavemeter covering the fre-
range of generator, using a microwave standard
quency range or a frequency standard setup. In
and suitable detector. (Test setup shown in Fig-
general when a new klystron oscillator tube is in-
ure 4-12.) If accuracy at lower frequencies is
stalled it will be necessary to slip the frequency
outside 1% tolerance, the dial can be slipped
dial slightly to bring into calibration. In some
slightly on its shaft to obtain desired accuracy at
cases, it may also be necessary to reset the plunger c
lower frequencies.
depth at the high frequency end of the band to re-
establish the correct high frequency limit. There 7) It may not be possible to achieve 1% overall
are no trimmers or other adjustment of that sort; accuracy with some replacement klystrons. In this
all adjustments for frequency recalibration must case try another klystron and repeat procedure.
be done mechanically.
4-14 REPLACING AND RECALIBRATING
To recalibrate the frequency dial following a change
THE ATTENUATOR
in klystron oscillator tube, proceed as follows:
It is not expected that the attenuator dial will
1) Set MOD. SELECTOR switch to CW. Theequip- require recalibration unless the attenuator as-
ment should be allowed a warm-up of at least 20 sembly is replaced. The attenuator is not ordi-
minutes before checking calibration. narily subject to change or breakage. Small im-
provements in accuracy may be made by slipping
2) Tune signal generator to 7650 on MEGACYCLES the attenuator dial on the front panel slightly on
dial. its shaft to bring into calibration.
3) Measure output frequency with wavemeter. If Following replacement of the probe, the attenu-
reading of MEGACYCLES dial is in error by more ator assembly must be adjusted for the correct
than approximately 100 megacycles, it will be and safe operating depth. The following discus-
necessary to remove plate that covers frequency sion is divided into two parts. The first concerns
drive assembly. the replacement of the attenuator probe, and the
second concerns the attenuator dial alignment.
4) With MEGACYCLES dial still set at 7650,
loosen set screws holding resonator plunger rods CAUTION
in drive bar, shown in Figure 4-11. Then manually
There are high voltages on V112 and V113 tube
move plunger rods in approximately 1/32 inch
shields. Turn off the instrument completely when
steps until output frequency is approximately 7650
replacing the attenuator and power monitor probe
megacycles as indicated by wavemeter. Tighten
assemblies.
set screws in drive bar in this position. --------- |
ACEC
