Model 683C Section 1V
Paragraph 4- 17
c. Remove wavemeters from setup.
CAUTION
Be careful that there are no holes across the
band due to either poor rf connections or
impedance mismatches.
d. RF LEVELER switch to ON.
e. Level the coarse grain power variations (fig-
ure 3-3) of the rf power output presentation
on the oscilloscope to the rf power-line curve.
ANODE VOLTAGE
(1) Adjust segment 1, R321 (figure 4-13) as
shown in step 1.
(2) Adjust segment 2, R324 (figure 4-13) as
shown in step 2.
(3) Adjust segment 3, R315, and segment 4,
R320 (figure 4-13) as shown in step 3. After
making all four adjustments readjust segments
1, 2, 3 and 4 as needed to obtain optimum
leveling action.
Note: There will be interaction between
-
segment 2 and segment 3 since the height to
which segment 3 rises is a function of the
parallel resistance of plate-load resistor R318
of V302A and R232, plus a section of R324.
This interaction makes available a wide range
of leveler shapes. There will also be a slight
interaction between segment 3 and segment 4
adjustments and dc level R332 adjustment.
f. Turn SWEEP SELECTOR to OFF.
g. Check power variation across the band. The
power spread across the band should be no
more than f 1.5 db. If out of specifications re-
touch segment potentiometers and dc level
adjustment as needed.
\3KMC w-3-273
h. Turn FREQUENCY dial to low power point; RF
LEVELER ON. With dc level potentiometer STEP 2.
R332 increases cathode current to 1 ma greater
than the value recorded in Blj.
i. Replace meter plate with new meter plate, if
meter plates do not agree.
j. With the RF LEVELER in the OFF position,
set balance R335 (figure 4-13) so that the
power level is greater than 30 mw at low
power point.
4-17. SERVICING THE SWEEP CIRCUITS.
A. VOLTAGES AND WAVESHAPES. The sweep
circuit can be very difficult to service if definite
conditions are not established. Figure 3-4 gives
typical wave shapes and dc levels of the complete
sweeping system. These voltages and wave shapes
are the same for any speed of sweep. If the sweep
rate is high, these wave shapes may be directly ob- ~KMC
served on a dc-coupled oscilloscope such as an @
Model 150A with a 10-megohm 10 pf probe such as w- 1-270
STEP 3.
an @ Model AC-21A. If this equipment is not avail-
able, it is possible to accurately measure the upper
01130-1 4-17 |
ACEC
HEWLETT-PACKARD
