TM 55-4920-244-14
two-position switch used to put the aircraft egt
c. Galvanometers. Galvanometer (12) is a
indicator in the circuit and to carry the indication
light beam galvanometers used during all tests
of the engine thermocouple harness back to the
other than RPM and insulation checks . Galv-
tester.
nometer (25) is also a light beam galvanometers
2-3. Operator's Instruments (Figure 2-1).
used during RPM checks.
a. Insulation Check Meter. The insulation
d. Percent Scale. The % scale (1) shows
check meter (8) indicates the resistance of the
thermocouple circuit. The scale is calibrated from
the reading of the RPM check circuit. The per-
0 to 500.
cent scale is calibrated in increments of 0.2 per-
b. Degree Scale. The potentiometer is
cent from 0 to 110 percent RPM, and is read
calibrated in degrees Celsius (in 1 increments)
and is read on the C scale (11).
when switch SW-7 is in RANGE position.
Section Il. OPERATION UNDER USUAL CONDITIONS
WARNING
2-4. General.
a. This section provides instructions for
Ground the tester with the
normal testing operations and basic capabilities
pigtail ground wire in the
of the tester, as well as coordinating these capa
power inlet cable before us-
bilities to perform the specific tasks for which
ing the tester.
the tester is designed.
c. Connect power inlet cable to connector
b. It is essential that the operator know
P-1 and to a 110 volt, 50 to 400 Hertz, ac
how to perform every operation of which the
power source.
tester is capable. Since nearly every testing as-
d. Connect heater cable to junction box
ment presents a different problem, it may be
and to tester at HEATER CABLE connector.
necessary to vary the given teat procedure to fit
e. Connect one heater probe over each
a specific testing assignment.
engine thermocouple in engine thermocouple
harness.
c. No special tools or equipment are
f. As each heater probe is placed over
needed by the operator to maintain or operate
engine thermocouple, connect it to junction box
the tester.
to keep cables straight on engine. Push heater
probes completely on engine thermocouples and
lock firmly in place.
Check (Figure 2-2).
NOTE
2-6. EGT System Circuit Check (Figure 2-3).
CAUTION
To check an engine not
installed in an aircraft, fol-
If a heater probe fails or is
low the procedures listed
defective before the start of
below, except that the
a test, there is a possibility
check cable must be con-
that the remaining heater
nected to the engine junc-
probes can be burned out
tion box and the tempera-
during increase of voltage
ture of the engine thermo-
r e g u l a t o r temperature.
couple harness is read on
Check heater probes per
o
the tester C scale. Refer
to engine manual for ap-
a. With heater probes connected to engine
plicable check cable
thermocouples, place switch SW-1 in T/C posi-
adapter.
tion and switch SW-2 in S-1 position.
a. Place switch SW-1 in OFF position.
b. Place switch SW-6 in MECH. ZERO
b. Place TEMP REGULATOR knob in
position and zero galvanometers by turning
zero position.
MECH. ZERO knob.
