TM 9-4120-357-14
4-11. General.
a.
Essentially suppression is attained by providing a low-resistance path to ground for stray currents. The
methods used include shielding the ignition and high-frequency wires, grounding the frame with bonding straps, and us-
ing capacitors and resistors.
b.
In the air conditioner, filters are used to absorb current surges in the dc control system. All make/break cur-
rent components such as switches, relays and solenoids are shielded in metal casings which are bonded to each other
and to the casing with grounding wires. The casing is grounded through the junction box to the ground wire of the electri-
cal supply cable, and through an external grounding stud on the rear control panel beside the condenser fan guard.
4-12. Interference Suppression Components.
The four filters making up the primary interference suppression component are identical. They are composed of a
choke coil, each end of which is grounded to the non-magnetic metal case through a capacitor. The operating charac-
teristics of the filters are as follows:
Current
5.0 amperes
Voltage
600 volts dc
250 volts at 60 cycle ac
257(125 )
Maximum ambient temp.
C
0.035 ohms
180 MH
Capacity
1.11-1.8 mf
Insertion loss, minimum
0.15 mc - 60 dB
0.5 mc - 90 dB
1.0 mc - 100 dB
10.0 mc- 80 dB
100.0 mc - 80 dB
400.0 mc- 80 dB
4-13. Replacement of Suppression Components.
a. Remove the filter assembly as follows:
(1) Remove the front access panel (figure 1-1) from the air conditioner by
unscrewing four panel fastener screws.
(2) Remove the junction box cover (figure 4-1) by
unscrewing four panel fastener screws.
WARNING
Disconnect power from the air conditioner before performing maintenance work on
the electrical system. The voltages used can be lethal.
(3)
Tag wires leading from filter for identification, and disconnect them from their outer components(transformer
fuse block, XF1, and terminal block, TB2).
(4) Remove the filter assembly (figure 2-1) from the junction box by
removing four (each) screws, washers and
lock washers.
b.
Disassemble the filter assembly as
directed in
the following steps. (See figure 4-2).
(1) Remove four screws (6) and four washers (5) from the top end cap (4), and carefully pull the end cap away
from the tube (9) far enough to expose the wires connected to the rectifier (8). Tag wires for identification.
(2) Slide wire terminals from the rectifier terminals, and set the end plate aside.
(3) Slide the filters (10,11,17,18) out of the tube if testing indicates need for replacement.
(4) Unsolder wires from a
defective filter, and solder the same wires to a
new filter.
4-15