TM 11-5826-225-35
(2) Signal substitution. Signal substitu-
ceeds 1.5 volt. Since the Rx1 range
normally connects the ohmmeter in-
tion procedures for the receiver (para
ternal battery directly across the test
2-6) enable the repairman to localize
leads, the excessively high current (50
a trouble quickly to a receiver circuit
ma or more) may ruin some tran-
or stage. An RF signal generator,
sistors in the circuit. For a safe cur-
audio oscillator, and oscilloscope are
rent that will not damage transistors,
units of test equipment (para 23e)
use the Rx100 range of Multi meter
that may be used in signal substitu-
TS-352/U.
tion procedures. Observe the caution
notice in paragraph 26a arid follow
(4) Test points. All wiring in this equip-
t h e signal substitution procedures
ment iS from point-to-point. The wir-
ing and component junction connec-
transistors may be avoided.
t i o n s are supported by insulated
(3) Stage-gain charts, The receiver stage-
standoff terminal studs. Any of these
gain charts (para 27) will help lo-
terminals may be used as a test point
cate difficult troubles that produce
as required. No test jacks are pro-
weak signals and should be used when
vided. The terminal studs used for
performing the signal substitution
testing and troubleshooting in the re-
procedures.
ceiver are shown on the main sche-
matic diagram (fig. 510 or 5-10.1) as
d. Isolation. After the trouble has been local-
TP1 ,TP2, ect .
ized (c above), the methods in (1) through
(5) Intermittent troubles. In all of these
(5) below will help in isolating the trouble
tests, the possibility of intermittent
to a defective circuit element.
troubles should not be overlooked. If
(1) Waveform analysis. Voltage readings
p r e s e n t , this type of trouble may
taken in some cases are difficult if
often be made to appear by tapping
not impossible to analyze because
o r jarring the equipment. Make a
these voltages vary with circuit con-
visual inspection of the wiring and
ditions (equipment operation). For
connections.
these circuits, waveforms must be
taken and compared with the wave-
(6) Resistor and capacitor color code dia-
forms provided.
grams. Resistor and capacitor color
code diagrams (figs. 4-11 and 5-1)
(2) Voltage measurements. This equip-
are provided to aid maintenance per-
ment is transistorized. When measur-
sonnel in determining the value, volt-
in voltages, use tape or sleeving (spa-
age rating, and tolerance of capacitors
g h e t t i ) to insulate the entire test
and resistors.
prod, except for the extreme tip. A
momentary short circuit can ruin the
23. Test Equipment Required
transistor. For these voltage measure-
ments, u s e Multitester ME-26/U
The following chart lists test equipment re-
(vtvm) or the equivalent.
quired for troubleshooting Direction Finder
Sot AN/ARN-83 and the associated technical
transistor damage, make resistance
manuals.
measurements in this equipment only
Caution: The receiver and inverter circuits
as necessary.
are transistorized. Use all precautions to avoid
transistor damage.
to test in transistor circuits, check the
a. Never connect test equipment (other than
open circuit voltage across the ohm-
multimeter and vtvm's) outputs directly to a
meter test leads. Do not use the ohm-
meter if the open circuit voltage ex-
transistor circuit; use a coupling capacitor.
2-2
Change 4
Previous Page
