TM 11-6625-622-40
b. Conditions for Test. Remove the test unit
d. Test Harness, Radio Set AN/URM-157 Volt-
from the transit case and remove the control
age Measurements. Prepare for voltage measure-
unit from the test unit; leave cable W5 connected
ments as follows:
to jack J19.
(1) Connect 27.5 volts dc to the DC IN con-
c. Measurements. Make the voltage and re-
nector, and 115-volt, 3-phase, 400-MHz ac to the
sistance measurements indicated in the charts in
AC IN connector on the test unit.
d through g below. If abnormal results are ob-
(2) Set AC switch S3 to ON, DC POWER
tained, replace the defective component or wire
circuit breaker CB1 to ON, and 618T2--OFF--
in. the case of the resistance measurements. Parts
618T-3 switch S1 to 618T-3.
location are indicated in figures 3-1, 3-2, and
33. Use the schematic diagram (fig. 3-11) and
(3) Make the measurements as indicated in
the wiring diagram (fig. 3-15) to trace the cir-
the chart below.
cuits and to isolate the faulty component.
Normal indication
Isolating procedure
Point of measurement
Between the following pins of 618T-2/3
No voltage at any of the pins indicates a faulty circuit
connector J1 and ground:
breaker CB1, or 618T-2-OFF-618T-3 switch S1.
Check continuity of wiring to components listed above.
1
Check continuity of components.
2
3
4
27.5 volts dc 5 No voltage at pins 4 and 16, but voltage It the other
13
pins indicates a faulty fuse or fuseholder.
14
15
16
17
Between pin 12 of J1 and ground.
No voltage at pin 12 indicates faulty AC switch S3 or
115 volts ac 10
fuseholder for #3 fuse f3. Check continuity of wiring
to components listed above. Check continuity of
components.
circuit breaker CB1 to ON, and 618T2/2B--
e. Test Harness, Radio Set A N / U R M 1 5 7 A
Voltage Measurements. Prepare for voltage meas-
OFF--618T-3/3B switch S1 to 618T-3/3B.
(3) Make the measurements as indicated in
urements as follows:
the chart below.
(1) Connect 27.5 volts dc to the DC IN con-
f. Test Harness, R a d i o Set AN/URM-157
nector, and 115-volt, 3-phase, 400-MHz ac to the
AC IN connector on the test unit.
measurements are to be made with no power
( 2 ) Set AC switch S3 to ON, DC POWER
applied to the test unit.
Point of measurement
Normal indication
Isolating procedure
Between the following pins of 618T-2/2B/
No voltage at any of the pins indicates a faulty circuit
3/3B connector J1 and ground:
breaker CB1, or 618-2/2B-OFF-618 T-3/3B switch
1
S1.
2
Check continuity of wiring to components listed above.
Check continuity of components.
3
4
27.5 volts dc 5 No voltage at pins 4 and 16, but voltage at the other
13
14
pins indicates a faulty fuse or fuaeholder.
16
16
17
Between pin 12 of J1 and ground.
No voltage at pin 12 indicates faulty AC switch S3
115 volts ac 10
or fuseholder for 3 fuse f3. Check continuity of
wiring to components listed above. Check continuity
of components.
3-2
