Generator and Excitation Circuit (cont.)
Trouble, Symptom & Condition
Test or Inspection
Corrective Action
Load contactor (K1) will not
close when control switch (20,
Fig. 1 is held in CLOSE
position. Generator running at
normal voltage. No fault lights
on. (cont.)
d. Defective load contactor
control switch (S5)
(20, Fig. 1).
Set AUTO-MANUAL switch (S1)
to AUTO position. connect a
jumper with test prods between
terminals “S” and “R” on the test
receptacle. If the contactor
closes, replace control switch.
e. Defective rectifier (CR6)
1-1; 5, Fig. 11).
Check rectifier output as follows:
With test receptacle terminals
“S” and “R” connected as above,
check voltage to rectifier
between terminals “R” and “H”.
Voltage should be 115-V AC.
With test receptacle terminals
“S” and “R” connected as above,
check rectifier output at load
contactor terminals X and Y. If
voltage is not at least 90 V DC,
replace rectifier.
Defective load contactor coil
(K1) )1-1; 6, Fig. 11)
Disconnect leads at load
terminals W and V. Check coil
resistance between these
terminals. Resistance should be
approximately 50 ohms. If coil is
defective, replace the complete
load contactor.
4.
Load contactor (K1) will close
when control switch (20, Fig. 1
is held in momentary CLOSE
position. Opens immediately
when switch is released to
center ON position.
a. 28.5-V DC is not reaching
plug-interlock relay (K2)
from aircraft for the
following reasons:
Check voltage at terminal Z on
test receptacle. Voltage should
be 28.5-V DC. If not, voltage is
not being supplied from aircraft.
Check causes as follows:
b. Generator to aircraft cable
connector defective or not
plugged into aircraft
receptacle connector.
Inspect cable connector plug
thoroughly for damaged E and
F terminals. Be sure the plug is
fully mated with the aircraft
receptacle connector and
making good contact.
c. Aircraft rejecting power.
Check aircraft on board
electrical equipment and
controls.
OM-2040 / Operation and Maintenance Manual
90D20 / Generator Sets
Chapter 3-1
February 28/94 Revised
Page 20
Summary of Contents for 6921 Series
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