Section V Model 204B
Paragraphs 5-31 to 5-35
b. Set Model 204B RANGE to X100, VERMER to holding the power supply and circuit board, then swing
center of its range, and AMPLITUDE to maximum the two assemblies to the side. Use figure 5-5 asa
clockwise position, guide, and proceed as follows:
c. Set FREQ. to 56 (5.6 kc). a. Orient cams as shown in figure 5-5a.
d. Lock FREQ. dial shaft with a number 8-32 b. Using a hex socket wrenchand 3/8-inch wrench,
socket set screw (dial shaft locking screw) which in- remove both cable terminal bolts.
serts into threaded hole on top of dial shaft housing . c. Remove terminal bolts from cable.
e. Loosen potentiometer (pot) shaft locknut, fig- d. On replacement cable, place a mark 6-7/8
ure 5-5a, and adjust pot by turning pot arm to obtain inches from the end,
a 5.6-kc output, e. Slide replacement cable through one terminal
f, Tighten pot shaft locknut, and loosen dial shaft bolt so that cable is orientated to terminal bolt as
locking screw. shown in figure 5-5a, lower left detail.
g. Set FREQ. to 5 (500 cps) and tightendial shaft f. With mark on the cable in center of terminal
locking screw. bolt as shown, install terminal bolt on dial cam.
h. Loosen dial shaft locknut and adjustdial cam g. Slide cable ends approximately 1/4 inch through
by turning cam to obtain a 500-cps output. second terminal bolt so that cable is orientated to
i. Tighten dial shaft locknut and loosen dial shaft terminalbolt as shown infigure 5-5a, upper left detail.
locking screw. h. Orientate the cams as shown in figure 5-5band
j. Repeat steps c through i untilfrequencies are use the figure as a guide. Slide the cable onto the
within approximately rtl%. cams, and install the second terminal bolt on the pot
k. Set RANGE to XlOK, FREQ. to 5 (50 kc), and cam. (The shorter cable length shouldpass over points
adjust C8 (figure 5-6) to obtain a 50-kc output. Aand B; the longer length should pass over D, B , and C .
m. Set FREQ. to 56 (560 kc), and adjust C15 i. Tighten both terminal bolts to remove all slack
(figure 5-4) to obtain a 560-kc output. If necessary, in cable and allow the dial to cover its full range. Do
change the value of C14 for proper range of C15. not overtighten cable.
j, Perform Frequency Calibration Adjustments ,
Note
(paragraph 5-29).
Check gain control voltage according to
steps a and b of paragraph 5-28. 5-34. FREQUENCY POTENTIOMETER
n. All frequencies across the band should be REP LAC EM ENT.
within *3%. 5-35. To replace the frequency potentiometer (pot),
RlOA and B, it is necessary to remove the pot cam .
5-31. REPLACEMENT PROCEDURES.
For easier access to the cams, remove the screws
5-32. CAM CABLE REPLACEMENT. holding the power supply and circuit board, then
swing the two assemblies to the side. Use figure 5-5
as a guide, and proceed as follows:
5-33. If it is necessary to replace the cam cable, a. Position cams as shown in figure 5-5a. Some
order it by @ Stock No. 8160-0003 and description. instruments have aluminum cams which have the
For easier access to the cams, remove the screws counterweight shown in figure 5-5. Other instruments
SHORT
TERMINAL LENGTH
COUNTERWEIGHT
.
.
PANEL BUSHING NUT
POT SHAFT LOCKNUT
WT
POT ARM CPM
CABLE
TERMINAL BOLT
POT CAM
DIAL SHAFT
SHORT DIAL
LOCKNUT
TERMINAL LENGTH CAM
--
DIAL CAM
LONG
LENGTH
SHOULD BE
IN CENTER CHASSIS TOP ....... LONG CABLE
LENGTH
b
Figure 5-5. Cams and Cable Relationship
5-6 01369-3 |
ACEC
