TM 55-1930-209-14&P-12
4-18.2.5.1 Test and repair
a.
With 24 Vdc circuit breaker 3P14 closed (ON), check for light on ON power control module. If lamp is not lit,
check for faulty bulb. If bulb is ok, check voltage at Inputs to power control module between points TB1 and TB4
for 24 Vdc (see Figures 4-8 and 4-9). If voltage is not 24 Vdc, go to step b. If voltage is 24 Vdc, go to step d. If
lamp is lit, go to step 1.
b.
Check voltage at circuit breaker 3P14 outputs for 24 Vdc. If voltage is 24 Vdc, go to step c. If voltage is not 24
Vdc, circuit breaker or power source is at fault.
c.
Check voltage at junction box between power control module and 24 volt panel for 24 Vdc. If voltage is 24 Vdc,
repair or replace wires from junction box to power control module. If voltage is not 24 Vdc, repair or replace
wires from junction box to circuit breaker 3P14.
d.
Check voltage at power control module between points TB2 and TB4 for 24 Vdc. If voltage is 24 Vdc, go to step
e. If voltage is not 24 Vdc, repair or replace jumper from TB1 to TB2.
WARNING
Make sure power control module is electrically dead before making continuity checks. Redtag
circuit breaker 3P14 with: "WARNING DO NOT ACTIVATE REPAIRS BEING MADE."
e.
Open (OFF) circuit breaker 3P14 and check fuse for continuity. If fuse is ok, go to step f. If fuse indicates open
circuit, replace fuse as given in paragraph 4-18.2 5 2.
f.
With ON/OFF switch in ON position, check continuity of ON/OFF switch between points E1 and E2. If check
indicates closed circuit, go to step g. If check indicates open circuit, replace ON/OFF switch.
g.
Close (ON) circuit breaker 3P14 and check voltage between points TB4 and G1 of lamp for 24 Vdc. If voltage is
24 Vdc, go to step h. If voltage is not 24 Vdc, repair or replace wire from TB2 to lamp point G1.
h.
Check voltage between points TB2 and E1 of ON/OFF switch for 24 Vdc. If voltage is 24 Vdc, go to step i. If
voltage is not 24 Vdc, repair or replace wire from TB4 to ON/OFF switch point E1.
i.
Check voltage between points TB2 and F1 of fuse for 24 Vdc. If voltage is 24 Vdc, go to step. If voltage is not
24 Vdc, replace wire from switch point E2 to fuse point F1.
j.
Check voltage between point TB2 and H1 of diode for 24 Vdc. If voltage is 24 Vdc, go to step k . If voltage is
not 24 Vdc, repair or replace wire from fuse point F2 to diode point H1.
k.
Check voltage between points TB2 and H2 of diode for 24 Vdc. If voltage is 24 Vdc, repair or replace wire from
diode point H2 to lamp point G2. If voltage is not 24 Vdc, replace diode.
I.
Check voltage outputs from power control module between points TB2 and TB8 or 24 Vdc. If voltage is 24 Vdc,
go to step n. If voltage is not 24 Vdc, go to step m.
m.
Check voltage between point TB2 and point D (termination point for white output wire) for 24 Vdc. If voltage is
not 24 Vdc, replace power control module as given in paragraph 4-18 2 5 2b. If voltage is 24 Vdc, repair or
replace wire from point D to TB8.
n.
Check voltage to Inputs of power amplifier between points TB1 and TB8 for 24 Vdc. If voltage is 24 Vdc, go to
step (1) . If voltage is not 24 Vdc, repair or replace cable from power control module to power amplifier.
(1) Check voltage at power amplifier between points TB1 and TB7 for 24 Vdc. If voltage is 24 Vdc, go to step
(2). If voltage is not 24 Vdc, replace jumper wire from TB7 to TB8.
(2) Check voltage between points TB1 and TB5 for 3.3 to 3 5 Vdc. If voltage is 3.3 to 3.5 Vdc, go to step (u).
If voltage is not 3 3 to 3 5 Vdc, replace power amplifier as given in paragraph 4-18.2.5.2c.
o.
If communication system is still not operating, test operation by using different handset mike and different
headset station that is operational. If operation is nonexistent, replace power amplifier. If operation is apparent,
replace handset or headset station as given in paragraph 4-18 2.7.2.
4-21
