LEGEND FOR FIGURE 4-8
Circuit board assy
Paralleling transformer T3
Filter choke L1
(shelf) of the AC-DC control box assembly.
To remove relay, close locking device
(under relay socket) and lift relay out of
socket. To replace plug relay in snugly,
until locking device is firmly in place.
Repair. Repair relays K1 and K50 by
replacement in accordance with paragraph
4-24. AC-DC CONTROL RELAY ASSEMBLY TB9.
The AC-DC control relay assembly (18, figure 4-10)
contains three terminal boards, two diodes (CR1 and
CR23), and eight relays:
Low fuel shutdown
Main CB control
DC voltage slave
Check each relay using test circuits
shown in figure 4-12. Energize each
set of relay contacts individually by
applying 24V DC directly to leads.
Check for open or closed contacts (no
continuity or continuity) as indicated in
figure 4-12. Check that each set of
contacts revert (to either closed or
open position) when deenergized. If
any relay fails to either open or close
as indicated, it is defective and must
Check diodes CR1 and CR23 for
polarity. A good diode will read high
resistance on way and low resistance
the other way. A defective diode will
read full scale both ways, or will read
infinity (no reading) in either direction.
Check terminal boards and printed
circuit wiring by repeating steps (1)
and (2), but apply 24V DC to TB9
Repair. If any of the relays or diodes are
defective, AC-DC Control Relay Assembly
TB9 is repairable by replacing the defective
component. If the printed circuit wiring, a
component proves defective, the entire
assembly must be replaced.
Remove relay assembly (18, figure 4-
10) as follows:
Tag and ten disconnect wires
from terminal boards.
Remove screws (19) to