TM 32-5835-005-14 & P
DIRECT
SUPPORT
MAINTENANCE
INSTRUCTION
Section
I.
GENERAL
7-2. Scope of Direct Support Maintenance.
The direct support maintenance procedures
This equipment is transistorized.
are not complete in themselves but sup-
When measuring voltages, use tape or
plement the procedures performed at the
sleeving (spaghetti) to insulate the
organizational category and include any
entire test prod, except for the ex-
additional techniques required to perform
treme tip. A momentary short can ruin
maintenance on the AN/UNH-17A.
a transistor. Make voltage and resis-
tance measurements as directed on the
7-3. Bench Testing.
voltage and resistance diagram using
the same or equivalent multimeter
Bench testing at the direct support
specified.
maintenance level of the AN/UNH-17A
shall be limited to the following:
b. Before using any ohmmeters to test
transistors, check the open-circuit
a. Testing power supply voltages.
voltage across the ohmmeter test leads.
Do not use the ohmmeter if open-circuit
b. Direct replacement of the record/
voltage exceeds 1.5 volts, since tran-
reproduce amplifier (A1A3), motor con-
sistors may be damaged.
trol servo board (A1A5), preamp board
(A1A8), bias oscillator and meter drive
c. Since the RXI range normally con-
board (A1A4), power supply board (A1A7)
nects an ohmmeter internal battery dir-
and control logic board (A1A6). See
ectly across the test leads, the com-
Figure 7-1. for component location.
paratively high current (50 ma, or
more) may damage a transistor under
test. Normally the RXI range should
not be used to test low power tran-
sistors.
d. Use a coupling capacitor to
connect test equipment (other than mul-
timeter or VTVM) to transistorized
circuits to prevent damage to transis-
tors.
e. Make certain POWER switch is in
OFF position, before connecting power.
Surge voltage may damage transistor
circuits.
f. Voltage measurements at the direct
support maintenance level are limited
to those measurements indicated in
Sections IV through XV. Measurements
beyond those indicated shall not be
performed at the direct support main-
tenance level.
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