TM 11-6625-847-45
Item
No.
Indication
Probable trouble
Procedure
and ground. Adjust the
AN/USM-140(*) to indicate a
+54-volt peak-to-peak square
wave having a pulse repetition
frequency(prf) of
approximately 5kc. If square
wave is not observed on the
AN/USM-140(*), check
transistorsQ1 and Q2, resistors
R1 and R2, and capacitors
C1 and C2 for defects.
Replace defective parts.
check primary and secondary
winding resistances of
transformer T1. If pri-
mary or secondary windings
resistances are abnormally
low (shorted) or high
(open), replace transformer
T1.
5
The +6.3-volt ac output
Defective +6.3-volt ac filter
Connect the ME-26(*)/U be-
from T1 is not indi-
circuits.
tween test points A2J1 and
cated on the ME-
A2J2, and check for 6.3 volts
26(*)/U when TEST
ac. If 6.3 volts ac is not present
SELECTOR switch on
at test points A2J2 and A2J1,
tray A1A1 is set to
check capacitors A2C5 through
position 5; however,
A2C8 and inductors A2L1 and
the + 125- and 33-
A2L2 for defects. Replace de-
volt dc outputs are
fective parts.
present for their re-
spective TEST SE-
LECTOR switch posi-
tions.
6
The AN/USM-140(*)
Same as 5 above -----------
Check parts of filter circuits for
shows excessive ripple
defects. Replace defective
for +6.3-volt ac out-
parts.
put.
7
The ME-26(*)/U does
a. Connect the ME-26(*)/U
not indicate -33 volt
circuit of -33-volt dc out-
between the anode of
output level when TEST
put.
Zener diode A3VR1 and
SELECTOR switch on
ground, and check for an
tray A1A1 is set to
indication of -33 volts dc.
position 4; however,
If -3 volts dc is not in-
the ME-26(0)/U in-
dicated, check diodes
dicates +125-volt dc
A3CR5 through A3CR8,
and +6.3-volt ac levels
capacitor A3C4, resistor
for the respective TEST
A3R2, and Zener diode
SELECTOR switch
A3VR1 for defects. Re-
positions.
place defective parts.
b. Defective -33 volt dc filter
b. If -33 volts dc is indicated
circuit.
at the anode of A3VR1
in a above, connect the
ME-26(*)/U between
test point A3J2 and ground,
and check for an indication
Change 1 2-9
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