P-9-TM-457-35 T.O. 35C2-3-442-2
TM-07464A-35 TM 5-6115-457-34
Section III. FAULT LOCATING INDICATOR BOX
transient d. c. voltage and frequency chatter
6-48.
GENERAL.
from causing a false malfunction indication.
The fault locating indicator box
6-49. TEST ON EQUIPMENT.
(A9) is a self-contained unit with solid
state circuitry. On its front panel are ten
a. Symptom and Isolation of Malfunc-
red malfunction indicators, each for a
tion. A malfunction of the fault locating in-
specific fault, a one ampere fuse to pro-
dicator box is usually the absence of a fault
tect against overload, and a two pole, two
indication during a fault condition. Another
position, spring loaded switch. The func-
malfunction is a false indication which can-
tion of the indicator box is to illuminate a
not be reset when a no fault condition exists.
particular malfunction indicator when one
To isolate the malfunctions proceed as
of the protective devices senses a malfunc-
follows :
tion and closes its malfunction signal con-
tacts. This causes a dc signal to be im-
pressed across a series parallel RC net-
NOTE
work for one of the ten SCR, silicon
controlled rectifier, circuits in the fault
Refer to figures 1-8 and 1-9 for cir-
locating indicator box (refer to figure 1-8).
cuitry, and component layout and
wiring.
When the voltage across the capacitor is
sufficient, the current to the gate of the
1. No Indication.
SCR will be sufficient to trigger it. The
particular indicator lamp in series with
(a) Press the switch S1 to TEST
this SCR will be energized. Relay K1 is
OR RESET, all the indicator lights DSl
also energized and its normally closed
through DS10 should illuminate.
contacts open to deenergize the fault signal
(b) Check for defective indicator
input to the SCR. When the switch is
lamp if one or two do not illuminate.
momentarily positioned to TEST or RESET,
the SCR will be turned off because its neg-
(c) If no lamp illuminates check
ative return from cathode is open. All in-
fuse F1.
dicator lamps will be energized, and relay
(d) If fuse F1 is not defective re-
K1 will stay energized. When the switch
move plug P12 and check pins A(+) and
is released back to normal position, and
B(-) for 24 VDC.
if the fault is cleared, the indicator lights
will de-energize and the circuit will be
(e) With the above requirements
q u i e s c e n t . If the malfunction is still
met and indicators not illuminating, check
present the SCR and indicator lamp for that
wiring to fault sensor. For example high
particular malfunction will again energize.
coolant pins C-K on connector P12 with
fault simulated should have continuity. Re-
With no malfunction input and the switch
momentarily positioned to TEST or RESET,
connect P12 and simulate a high coolant
fault if indicator lamp DS7 does not illumi-
all indicator lamps will energize. With its
nate, repair or replace the fault indicator
release again, all lamps will be de-ener-
box. Similar tests procedure will apply to
gized and the circuit is again quiescent.
remaining faults.
The purpose of capacitor C 11 is to block
6-22
