TM 11-6625-847-45
Section II. TROUBLESHOOTING CHARTS
2-18. Troubleshooting Chart, Test Set (Dc-to-Dc Converter and Regulator Module A3)
Note. Attach tray A1A1 to the Test set. Refer to paragraph 2-7 before using chart.
Item
No.
Indication
Probable trouble
Procedure
1
The + 20 volt dc output
Defective series regulating
Connect the ME-26 (*)/U
level is not indicated
transistor 1A1Q1.
between test point J11 on tray
on the ME-26(*)/U
A1A5 and ground. Check
when the TEST
for an indication of +20
SELECTOR switch on
volts dc. If +20 volts dc is not
tray A1A1 is set to
indicated, check transistor
position 2
1A1Q1 in the test set for
defects. Replace defective parts,
2
The + 1 volt dc con-
Defective +20-volt dc regulating
Se LOAD SELECT switch on
verter output does
circuit
tray A1A1 to 500, and make
not stay within the
the voltage measurements in
limits of +19.1 to
a through d below using the
+19.9 volts (LOAD
ME-26 (*)/U.
SELECT switch on
tray A1A1 set to 100)
and +19A to +19.6
volts (LOAD SELECT
switch on tray
A1A1 set to 500)
when the primary dc
source connected to
the test set is adjusted
to +27 and
+20 volts respectively.
a Connect the ME-26(*)/U
between the emitter of
transistor A1Q4 ad grand
Check for an indication of
+4.0 volts de. If +4.0
volts dc is not Indicated,
check resistor A1R6 and
transistors A1QS and
A1Q4 for defects. Replace
defective parts.
b. If the ME-26(*)/U indicates
+4.0 o dc in a
above, connect the ME-
2W(*)/U between the base
of transistor A1QS and
ground and check for an
indication of +4.8 volts
de. If Indication is not
approximately +4.8 volts
de, check Zener diode
A1VR2 and resistors
A1R2 and A1R4 for
defects. Replace defective
parts.
2-7
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