56. Isolating Troubles in Assembly A7500
(3) Adjust the TS-382F/U frequency to
100 cps while maintaining an ME-
Refer to figure 39 for circuit details and
30 B/U indication of 50 mv. A nor-
mal indication should be +1.5 volts
a. Checking Inductor L7501, Potenti-
dc 0.4.
ometer R7501, and Capacitor C7503.
(4) Adjust the TS-382F/U frequency to
(1) Remove assembly A7500 from the
3,000 cps while maintaining an ME-
TS-1777/VRM-l.
30 B/U indication of 50 mv. A nor-
(2) Check the continuity of inductor
mal indication should be +3.0 volts
L7501, potentiometer R750.1, and
dc 0.4.
capacitor C7501 to locate the faulty
(5) If the indications obtained in (3) and
part.
(4) above are normal, trouble iso-
b. Filter FL7501 Insertion Loss.
lation is complete.
(1) C o n n e c t a 50-ohm 5-percent, 1-
(6) If the indications obtained in (3) or
watt, composition resistor between
(4) above are low, proceed to d
connector P7501-C and P7501-D.
below.
(2) Connect Hf Signal Generator output
d. Isolation.
t e r m i n a l s and the input terminals
(1) A d j u s t the TS-382F/U for a fre-
of Wide Band Amplifier 460AR and
quency of 1,000 cps at a level of
R f Millivoltmeter 411A between
160 mv as indicated on the ME-
connector P7501-M and P7501-L.
30B/U.
(3) C o n n e c t the AN/USM-26 to the
(2) Measure the listed signal and dc
460AR.
voltages given in the chart below to
(4) Adjust the 606A output frequency to
isolate the faulty part. Measure the
5.65 mc 100 cps as indicated on
a c voltages with an ME-30B/U;
the AN/USM-26 for a 0-db indica-
m e a s u r e the dc voltages with an
tion on the 411A.
ME -26B/U.
(5) Move the 411A to connector P7501-
(a) Signal voltage chart.
C and P7501-D, and record the db
i n d i c a t i o n . A normal indication
Circuit junction
Signal Voltage (rms)
noted should be an insertion loss
I
of 6 db or less.
160 mv
P7401-M
160 mv
Q7401 base
(a) If the indication obtained exceeds
160 mv
Q7401 emitter
the 6-db insertion loss, replace
10 mv
Q7402 base
filter FL7501.
Q7402 collector
2.5 v
9 mv
Q7403 base
(b) If the indication is normal, pro-
ceed to c below.
(b) DC voltage chart.
c. Filter FL7501 Bandwidth.
(1) Per for m the procedures given
+dc voltage to
Circuit junction
ground (Volts)
i n b(l) through (3) above. -
I
(2) Adjust the 606A output frequency
P7401-H
16
Q7401 base
to 5.6555 mc to 100 cps as indi-
8.95
Q7401 emitter
8.4
cated by the AN/USM-26 and for
13.8
Q7402 base
a 0-db indication on the 411A.
6.0
Q7402 collector
(3) Move the 411A to connector P7501-
14.0
Q7403 base
14.1
Q7403 emitter
C and P7501-D. The normal in-
2 . 0 (rectified
P7401-K
dication should be less than 6 db
signal)
down.
(3) Remove the test signal and set the
(4) Move the 411A to connector P7501-
T S - 1 7 7 7 / V R M - 1 ON-OFF switch
M and P5701-L and adjust the 606A
to OFF.
frequency to 5.6554 mc 100 cps as
(4) Replace the faulty part.
indicated by the AN/USM-26 and
(5) R e p e a t b and c above.
for a 0-db indication on the 411A.
57
