Inverter Repairs - continued

TM 11-6130-377-14

(8) Remove

the

eight

screws

and

(26) Perform a function verification (para 6-22)

to check for proper performance.

lockwashers securing the heat sink assembly to the left

side of the heat sink duct.

c. Diode A1CR3 (A1CR5).

(1) Position DC circuit breaker A1CB1 to

CAUTION

OFF.

Use care not to damage or loosen

(2) Open front indicator panel.

leads connected to the heat sink

(3) Remove seven screws and lockwashers

assembly.

securing the vent panel to the left side panel. Remove

the vent panel.

(9) Carefully move the heat sink assembly to

(4) Unsolder wire No. 52 and 53 from A1CR3

the right and lift it forward to gain access to the

(A1CR5).

mounting.

(5) Measure the forward and reverse

(10) Tag all electrical leads attached to the

resistance of A1CR3 (A1CR5). If shorted, replace the

diodes to ensure proper reassembly.

defective diode as follows:

(11) Disconnect the electrical leads going to

(6) Remove the nut and lockwasher securing

the diode to be removed.

the diode to the bracket and remove the diode.

(12) Remove the diode using a one and one

(7) Install the replacement diode in the

quarter inch open end wrench and a one and one eighth

bracket and secure with the lockwasher and nut.

inch socket mount on a torque handle.

(8) Solder the electric wires nos. 52 and 53

(13) Redistribute

the

silicone

dielectric

to their respective terminals.

compound on the heat sink and apply a small amount of

(9) Position the vent panel on the left side

the compound on the new diode.

panel and align the screw holes. Install the seven

(14) Wrap the diode stud threads with two to

lockwashers and screws and tighten screws.

three turns of Permacel 2 mil Kapton E 6761 1/2 inch

(10) Close the front indicator panel and secure

wide tape.

with four captive screws.

(15) Replace cracked or broken mica

(11) Perform a functional verification (para 6-

insulating washers with Delbert-Blenn MW 1.625-

22) to check for proper operation.

.75.006 mica washers.

d. Thyristor (SCR) (A1Q2) (1973 Model Only).

(16) Position new diode on the heat sink and

(1) Position DC circuit breaker A1CB1 to

torque the retaining nut 250 to 325 inch pounds.

OFF.

(17) Test diode prior to installation of leads,

(2) Open front indicator panel.

high pot the diode to heat sink at 500 vac RMS. There

should be no breakdown or leakage current.

(3) Disconnect the electrical connector A1P1

from its receptacle A1A2J1 on the inverter drive circuit

(18) Reconnect the electrical leads to the

board A1A2.

diode.

(4) Remove four screws securing the inverter

(19) Position heat sink assembly in heat sink

drive circuit board A1A2 and remove the board.

duct and secure with eight screws, lockwashers and flat

washers.

(5) Remove ten screws, lockwashers and flat

washers securing heat sink duct cover to heat sink duct

(20) Position heat sink cover on heat sink duct

and remove cover.

and align screw holes.

(6) Disconnect electric lead (wire No. 49)

(21) Install ten screws, lockwashers, and flat

from anodes of diodes A1CR6 and A1CR7.

washers in their respective holes and tighten screws.

(7) Remove screen from heat sink exhaust

(22) Position the inverter drive circuit board

(front opening on right side panel).

A1A2 on the stand-offs of the heat sink cover and align

the mounting holes.

(8) Measure the resistance between wire no.

49 and the flag terminal (cathode) of SCR A1Q2. If a

(23) Install four screws and lockwashers and

short is evident replace A1Q2 as follows.

tighten screws.

(9) Working from the front panel opening

(24) Connect plug A1P1 to its receptacle

remove the two bolts and washers located on the

A1A2J1 on the inverter drive circuit board A1A2.

underside of the heat sink tunnel, securing the No. 2

(25) Close front indicator panel and secure the

heat sink assembly.

four captive screws.

Change 1

6-9