Model 652A
b. Set 652A controls as follows:
FREQUENCY RANGE . . . . . . . . . . . . . . X l K
FREQUENCY dial . .
. . . • . . . . . . . . •
.
• . . •
1
OUTPUT ATTENUATOR
. • . . . . . . . •
3.0 V
AMPLITUDE (COARSE
and FINE)
. • . . . . . . • . .
Extreme Clockwise
c. Adjust A2R17 for minimum distortion which should
be less than 1
%.
5·29.
Frequency Dial Calibration.
a. Preliminary mechanical adjustments (Perform only if
necessary).
1 . To prevent gear backlash problems during align
ment, make sure that there is no movement
between MPI and MP2. See Figure 6-1 . (They
must be pressed tightly together.) Also MP3, 4,
and MP5 spring gear assembly must be under
tension.
2. Check to make sure that the stop MP6 prevents
the tuning capacitor from being completely
closed. MP6 should hold the capacitor at least
1 / 1 6 inch open. Adjust if necessary.
3. With the dial set to maximum clockwise position,
slip the dial face such that the first mark left of 1
is l / 1 6 inch to the right of the fixed indicator. To
slip dial, remove Frequency dial knob and loosen
4 dial retaining screws. After slipping dial, reo
tighten the screws.
b. Attach test lead to A2TP2 ; lead should be connected
so that A2TP2 voltage can be monitored with bottom cover
in place. Replace bottom cover. Care should be taken that
test lead does not short to oscillator shield or instrument
chassis. Do not remove oscillator shield; it affects calibra�
tion.
c. Connect equipment as shown in Figure 5�8 and set
652A controls same as Paragraph 5-2Sb.
d. Set the 652A controls as in Paragraph 5-28(b). Ad
just A2R I 6 for · 370 mV ± ,l( mV at A2TP2.
10
e . Set 652A FREQUENCY dial extremely counter
clockwise and adjust S I C2 and S I C7 alternately for
counter indication of 1 0.2 kHz and A2TP2 voltage equal to
voltage recorded in Step d.
f.
Turn 652A FREQUENCY dial to extreme clockwise
position; counter should indicate frequency of 965 Hz to
970 Hz; if not, loosen tuner coupler (MP6, Figure 7- 1 ) and
slip tuner until specified frequency is obtained. (See
CAUTION).
Section V
g. Set 652A FREQUENCY dial for a counter indication
of I kHz. Dial should read I ; if not, carefully perform
following procedure :
I . Remove FREQUENCY dial .knob and loosen four
dial retaining screws.
2. Slip FREQUENCY dial to read I wilh coun ter
indication of I kHz.
3. Tighten retaining screws and replace knob.
h. Readjust A2RI6 to - 370 mV ±
l\
mV at A2TP2.
10
i. Set 652A FREQUENCY dial to 10. Readjust SI C2
and SI C7 alternately until count,r indicates frequency of
1 0 kHz and an A2TP2 voltage of - 370 mY.
j. Reset MP6 stop so that " 1 0" on the dial can be
turned to a position approximately 1 /8 inch to the left of
the fixed indicator.
The adjustments in Paragraphs 5-30 through
5-33 are highly critical. The values of the range
switch resistors were bridged at the factory for
op timum performance, and theoretically
should never have to be changed. Double
check the instrument perfonnance before
changing the values of any of the range switch
resistors.
5-30. X1 K
Range Adjustments.
a. Set 652A FREQUENCY RANGE to XI K and FRE
QUENCY dial to 1 .
b. Remove 652A bottom cover and oscillator shield.
Connect ac voltmeter with 1 kilohm resistor in series to
A2TPI and ground. Replace oscillator shield and bottom
cover.
c. AC Voltmeter should indicate 1 1 0 ± 1 0 mV rms. If
A2TPI voltage is not in tolerance, adjust A2RI6 to bring
voltage within specified limits (increasing A2Rl6 decreases
A2TPI voltage, and vice versa).
d. The de voltage at A2TP2 should be between
400 mV and - 320 mY, If not, change the value of SI R5*
and Sl RIS* simultaneously (See Table 5-6) until A2TP2
volta'ge is within tolerance and frequency is 1 kHz. Do not
solder the resistors in place.
e . Repeat Steps c and d o f this paragraph (if necessary)
until A2TP I , A2TP2 and the frequency are all within
tolerance. Solder SI R5* and SI R I S * in place.
5- 1 1
