(10) Reach in through the forward opening in
(1) Open the front indicator panel to gain
the left side panel and carefully lift the heat sink
assembly and bring it out of the tunnel.
(11) Tag the electrical leads and components
(2) Remove connector A1P1 and code plug
attached to the terminals of SCR A1Q2 for proper
A1P2 from the serviceable inverter drive circuit board.
reassembly. Remove the electrical leads from the SCR
(3) Remove four screws securing the inverter
drive circuit board to the heat sink cover and remove
(12) Remove the nut and lockwasher securing
inverter drive board.
the SCR to heat sink No. 2 and remove SCR A1Q2.
(4) Remove ten screws securing the heat sink
(13) Install replacement SCR into mounting
cover to the heat sink and remove cover to gain access
hole of heat sink No. 2 and secure using lockwasher
to connector A1P3. Disconnect A1P3 (para 6-8).
(5) Cover the lower front chassis area of the
inverter with a rubber mat or suitable insulating material.
components on the terminals of the SCR A1Q2.
(6) Install connector A1P1 and code plug
(15) Slide heat sink No. 2 into the heat sink
A1P2 to the inverter drive circuit that is to be tested and
duct tunnel and align the mounting holes of the tunnel
place the board on the insulating material.
and the stand-offs. Secure with lockwasher and bolts.
(7) Connect the variable DC source DDC
(16) Install the screen on the mounting
2592, or equivalent, to the input terminals of A1TB1 (fig.
brackets of the heat sink exhaust.
(17) Connect electric lead (wire No. 49) to the
(8) Pull out the plunger of the door interlock
anodes of diodes A1CR6 and A1CR7.
switch A1S1 to enable the inverter to operate with the
indicator panel open.
(18) Position the heat sink duct cover on the
heat sink duct and align the mounting holes.
(19) Install the ten screws, lockwashers, and
1. The inverter drive circuit board
flat washers in their respective holes and tighten screws.
is coated with acrylic lacquer;
(20) Position inverter drive circuit board A1A2
therefore, it may be necessary to
on the standoffs of the heat sink duct cover and align
scratch the various components or
the mounting holes.
leads to make a good electrical
(21) Install four screws and lockwashers and
(22) Connect plug A1P1 to its receptacle
2. When touching transistor leads,
A1A2J1 on the inverter drive circuit board A1A2.
make certain no other surface is
(23) Close front indicator panel and secure the
four captive screws.
3. Turn off the dc input source
(24) Perform equipment verification (para 6-
BEFORE making test equipment
22) to check for proper performance.
Inverter Drive Circuit Board A1A2 Testing
Preliminary Procedure for Testing and
Upon completion of each fault isolation and repair,
The inverter drive circuit board A1A2 can be tested and
reinstall the inverter drive circuit board into the inverter
repaired by electrically attaching it to an inverter in a
and perform a functional verification of the unit
known operable condition. In this setup the power static
operation per paragraph 6-22. Connect the equipment
inverter acts as a test fixture when used in conjunction
as described in paragraph 6-8 to perform the following
with the variable DC source DDC 2595 (or equivalent).
a. To install the inverter drive circuit board into the
inverter and prepare for checkout, proceed as follows: