DC Circuit Breaker A1CB1

TM 11-6130-377-14

Symptom

Failure Isolation and Repair

(A2U5-12)

480 Hz + 5v p-p

(A2U4-12)

4.8 KHz + 5v p-p

(A2U3-12)

48 KHz + 5v p-p

(A2Q5-Collector)

480 KHz + 5v p-p

(4) Replace the component that has an input but no

output.

(5) If there is no waveshape on (A2Q5) collector, re-

place (A2Q1), (A2Q2), (A2Q3), (A2Q4), (A2Q5) and

(A2CR1).

d. In parallel operation, both inverter DC circuit breaker

d. Replace A2UlO on both the A1A2 in the master inverter

fail to operate when sensors are tripped.

and A1A2 in the slave inverter.

e. Inverter turns on intermittently and then runs properly

e. Check the voltage on A2Q18 collector. At turn on this

after starting. It can be seen that relay A1K3 does not

voltage should stay at 110 vdc for 300 to 400 milliseconds

close (1973 model only).

(ms) and then go to 1 volt maximum.

(1) If the collector of A2Q18 does not drop to 1 volt,

check the following voltages:

A2Q9 collector-at turn on of A1B1, stays at zero

for 300 to 400 milliseconds (ms) and then goes to

+5 vdc.

A2Q10 collector-at turn on of A1CB1, stays at +5

vdc and then goes to zero after 300 to 400 milli-

seconds.

A2Q7 collector-at turn on of A1CB1 stays at zero

and then goes to +0.6 vdc after 300 to 400 milli-

seconds.

A1A2C9(+)-at turn on of A1CB1 rises from zero

to about +7.5 vdc and then stays at the final

voltage.

(2) Replace the component or components that do not

exhibit the proper waveshape at turn on of A1CB1.

f. Inverter starts but will not drive a load (resistor A1R6

f. Turn off inverter and disconnect A2P1.

gets very hot) (1973 model only).

(1) Check the resistance between A2Q16-C and -E. If

this resistance is less than 100 ohms, replace A2Q16.

(2) If A2Q16 is not shorted collector to emitter, discon-

nect A1J3 from A1P3 and reconnect A2P1.

(3) Turn on A1CB1 and make the following checks:

A2Q15-C

+0.2 to 0.3 vdc

A2Q9-C

+5 vdc

A2Q10-C

+0.2 to 0.3 vdc

A2Q15-B

+0.6 to 0.7 vdc

(4) Replace faulty components.

g. The inverter will not run but A1CB1 does not trip.

g. Check A1A2 inverter drive board. Replace board, deter-

mine that trouble is corrected.

h. Low output but inverter operates.

h. Possible overload condition on the output.

(1) Possibly A1A3 is open. Remove one lead of A1C3

and remove the jumper from inside. Check each capacitor

(8) with a multimeter to make sure it is not open. Replace

faulty capacitor(s).

(2) Check output load for shorts.

6 11.

DC Circuit Breaker A1CB1

b. Open the front indicator panel to gain access to

(fig. 2-1 and 3-1)

DC INPUT terminal board A1TB1.

To remove and replace the DC circuit breaker A1CB1

c. Disconnect DC input electrical cables from

proceed as follows:

terminal board A1TB1.

a. Shut down the DC source from the generator.

d. Tag all electrical leads to ensure proper

reassembly.

Change 1

6-12