TM 11-6125-252-15
a. Unit Fails to Start.
What to check
Possible causes
Remedy
No dc input; open in dc circuit ---
Inspect dc wiring inside of filter box.
Correct faulty wiring inside filter box.
Test dc components in filter box. See
Replace faulty dc filter components.
See figures 5-1 and 5-2.
Dc brush not making contact ----
Check for weak or broken brush spring.
Replace faulty brush spring. Replace
any brush worn below 1/2 inch, Refer
Measure brush length for worn brush-
es. Check brushes for free movement
to paragraph 4-8 b.
in holders.
Armature jammed --------------
Remove inspection cover and try to turn
Refer to paragraph 5-6. Replace broken
it by hand. Check the bearings. Check
brush causing jamming. Remove for-
for foreign material or broken brush
eign material around armature. Check
bearing alignment. Refer to depot cate-
causing jamming.
gory for replacement of bearings.
b. Unit Runs but Does not Deliver Current.
Remedy
Possible causes
What to check
Repair or replace faulty part.
Open ac circuit -----------------
Inspect ac wiring and connections. Test
filter coils.
Replace broken spring. Clean brushes
Ac brushes not making good
Inspect for weak or broken brush spring
and brush holders. Replace worn
contact.
brushes.
in holders. Check brush length against
wear line.
Test wiring. Test filter capacitors under
Partial short in ac circuit -----
Repair or replace faulty wiring. Replace
capacitors.
load.
c. Low Ac Output Voltage.
Remedy
Wkat to check
Possible causes
Correct cause of low dc input voltage.
Low dc input voltage ------------
Test dc input voltage ----------------
See b above.
Partial short in ac circuit ------
See b above -------------------------
d. Speed or Frequency Above or Below Normal.
Remedy
Possible causes
What to check
Correct cause of high or low input
High or low dc input voltage -----
Test dc input voltage -----------------
voltage.
e. Excessive Sparking at Brushes.
Remedy
Probable cause
What to check
Adjust brush holder.
Brushes out of position ----------
Check position of brush holder ----------
Replace broken spring.
Check for broken brush spring ---------
Check for broken or cracked brushes.
Brush sticking in holder ------------
Clean brush and brush holder.
Check for free brush movement ----------
Reduce load.
Overload on unit ---------------
Check load for shorts -----------------
f. Unit Overheats.
Remedy
What to check
Possible Causes
Unit overloaded -----------------
See e above --------------------------
See e above.
Clean ventilating air screens.
Poor ventilation ----------------
Inspect ventilating air intake and outlet.
g. Bearings
Overheated.
Remedy
What to check
Possible cause
Adjust seating of endbells.
Bearings misaligned -----------------
Check fit of endbells -----------------
h. Noisy Operation.
Remedy
What to cheek
Possible cause
Tighten mounting bolts.
Inspect mounting
bolts
--------------
Unit is loose ---------------------------
5-3
