TM 11-6625-441-34
POWER. If the voltage is higher or lower than
resistance is zero, check the +28-volt dc circuit
27.5 + O.5 volts dc, then readjust the output of
wiring for shorts.
the power supply for the correct voltage.
(2) Disconnect the multimeter test probes
from the +28V and the GND binding posts and
3-5. Troubleshooting of Interphone Test Set
connect the test probes to the AUDIO OSC and
the GND binding posts. Rotate INPUT SEL
outline procedures for localizing troubles to a
switch S3 to T. The multimeter should indicate
specific part within the interphone test set. Refer
approximately 5,000 ohms. If the resistance is
to figures 3-1 through 3-4 for parts locations.
low, check resistors R2 and R3. If the resistance
When voltage and/or resistance measurements
is zero, check the AUDIO OSC. circuit for shorts.
are required refer to paragraph 3-4.
(3) Rotate the INPUT SEL switch S3 to R.
b. Use of Troubleshooting Table. T h e
The multimeter should indicate 150 ohms. If the
troubleshooting tables supplement the equipment
resistance is low, c h e c k resistor R3. If the
s e l f - t e s t procedure (TM 11-6625-441-12). If
resistance is zero, check the AUDIO OSC circuit
previous self-tests have resulted in reference to a
for shorts.
particular malfunction then go directly to that
(4) Leave one multimeter test probe in the
item
in
the
table.
covers
GND binding post and connect the other test
troubleshooting information for the TS-1588/AIC
probe to contact pin 3 of plug P1. The multimeter
a n d table 3-2 provides troubleshooting in-
should indicate 5 ohms. If the resistance is low,
formation for the TS-1588A/AIC. If no known
check resistor R2. If the resistance is zero, check
symptoms
are
available,
begin
then
pin 3 of P1 for a short circuit to ground.
troubleshooting by performing the equipment
(5) Disconnect the multimeter test probes
self -test procedure until a symptom occurs.
from pin 3 of plug P1 and the GND binding post.
Locate the symptom under the malfunction
c. Voltage Measurement ,
column of the troubleshooting table and find the
WARNING
probable cause and corrective act ion next to the
28 VOLTS DC, 1 AMPERE is exposed
particular symptom.
when the interphone test set chassis is
CAUTION
removed from its case.
If operational symptoms indicate the
possibility of short circuits within the
(1) Set multimeter to indicate dc volts.
interphone test set, make the resistance
(2) Connect the multimeter test probes to
measurements described in paragraph 3-
the +28 V and GND binding posts on the in-
4 b before applying power to the
terphone test set front panel.
equipment.
(3) Connect the interphone test set power
c. Repair Procedures. Repair procedures for the
cable to a 27.5 + 0.5 volts dc power source.
interphone test set are contained in paragraphs 3-
(4) Connect the red insulated battery clip to
6 through 3-12.
the plus side of the line, and the black insulated
d. Direct Support Testing. T e s t i n g i n -
clip to the ground side.
structions which must be performed after any
(5) The multirneter must indicate 27.5 + 0.5
repairs are made are contained in paragraph 3-13.
volts dc when POWER-OFF switch S7 is set to
Table 3-1. Troubleshooting of Tes t Set, Radio TS-1588/AIC.
Probable cause
Corrective action
Malfunctwn
1. OPERATE lamp DS1 fails to go
No dc power applied to interphone
Check connections to power source.
test Set.
on when POWER-OFF switch S7
is set to POWER.
Defective lamp DS 1.
Replace defective lamp DS1.
Defective lampholder XDS1.
Replace lamoholder XDS1 (fig. 3-1).
Replace fuse F1.
Defective fuse F1.
Replace fuseholder XF1.
Defective fuseholder XF1.
Replace switch S7.
Defective POWER switch S7.
Replace relay K1.
Defective self-test relay K1.
Defective wiring.
Repair or replace defective wiring.
Replace relay K 1.
2. SELF TEST lamp DS2 fails to go
Defective self-test relay K1.
Replace receptacle J8 (fig. 3-2).
on and OPERATE lamp DS1 fails
Defective SELF TEST RECEP-
TACLE J8.
to go out when SELF TEST
RECEPTACLE J8 is mated with
Repair or replace plug P1.
Defective test cable plug P1.
Defective wiring,
test cable plug P1.
Repair or replace defective wiring
3-2
