Adjust potentiometer until voltage
begins to increase on panel 400 Hz AC voltmeter, and
increase voltage to 120V AC line-to-neutral.
If load contactor trip Indicator Illuminates
due to under-voltage, reset load contactor
switch and increase voltage to 120V AC
If 120 volts are obtainable and the
load contactor does not trip, the 400 Hz generator output
is correct and the voltage regulator has failed. If 120
volts are not obtainable, the generator or other 400 Hz
components are defective. Refer to paragraph 4-62 for
400 Hz generator maintenance instructions.
Installation. Install voltage regulator in
reverse order of removal.
Relay assemblies K2,K3,K4 and K5 through K9
Tag and disconnect wiring harness
connector plug on relay assembly.
Remove six (6) attaching screws
and washer and remove relay assemblies from upper
electrical power chassis.
Cleaning and Inspection.
Clean relay assembly with filtered
compressed air or wipe with a clean rag moistened with
an approved cleaning solvent. Clean receptacle with
filtered compressed air or an electrician's brush.
Visually inspect relay assembly for
corrosion, cracks, damaged threads or other evidence of
Remove connector P3 from relay
assembly (K2,K3,K4) and connect a source of 24V DC
across pins S and H on relay assembly connector J3.
Check for continuity between pin M
and N, pin A and L, and pin P and R.
connection at pin S to pin G so that the 24V DC is
connected across pins G and H of connector J3.
between the four pins A, B, C and D. Check for
continuity between pins P, K and R. Check for
continuity between pin E and pin F, pin S and pin J, and
pin V and pin W.
Disconnect the 24V DC source from
connector J3. If continuity is not present between the
pins specified in steps (b) and (d), the relay assembly is
Remove connector P4 from relay
assembly K5 through K9 and connect the positive side
of a source of 24V DC to pin E and the negative side to
pin F on the relay assembly connector J4. Check that
there is continuity across the following pins on connector
J4: K and L, H and J, M and Q, G and D.
Without removing the 24V DC
connections from pins E and F, jumper the positive side
of the source so that it is connected to both pin E and
pin W (pin F is a common negative for both relay coils).
The circuit between pins M and Q should now check
Remove the positive jumper from
pin W and connect it to pin e so that the positive 24V
DC is not connected to pins E and e. Jumper the
negative side of the voltage source to pin f, so that the
negative 24V DC is connected to both pin F and pin f.
The circuit between pin G and pin d and between pin Y
and pin Z should check open. The circuit between pins
b and c should show continuity.
Remove the jumpers from the
connector and connect the 24V DC source across pins t
and F. Check for continuity between pins a and s, and
between pins n and p. There should be continuity.
connections to place the 24V DC across pins W and X.
Check for continuity between pins R and S, and for
continuity between three (3) pins T, U and V.
Check for continuity between pins Y and Z, C and B, g
and h, and between the three pins A, 0 and N. If the
circuit between pins does not check as outlined in steps
(f) through (k), the relay assembly is defective.
Installation. Install replacement relay
assembly in reverse order of removal.
Protective Panel (two used, 60 Hz and 400 Hz).
Removal. Tag and disconnect wiring
figure4-37. Remove six (6) attaching screws and
washers and remove protective panel.
Cleaning and Inspection.
Clean protective panel assembly
with filtered compressed air or wipe with a clean rag
moistened with an approved cleaning solvent. Clean
Visually inspect panel for corrosion,
cracks, damaged threads or other evidence of damage.
Test. If either the 400 Hz main contactor
trip indicator lamp or the 60 Hz load contactor trip
indicator lamp illuminates and 60 Hz or 400 Hz power is
lost, reset the 400 Hz main contactor switch or the 60 Hz
load contactor switch, as applicable. If the system trip
indicator lamp again illuminates and power is lost, the
protective panel for the applicable system has failed.
If upon resetting either the 60 Hz load
contactor or the 400 Hz main contact
switch, the system ammeter pegs full
scale, check for a short circuit or overload
condition in the system.