CHAPTER 2
TROUBLESHOOTING
Warning: When servicing the tube tester, be very careful of the high voltages. Always dis-
connect the tube tester from the power source before removing the chassis from the case. Before
touching any exposed portion of the circuitry with the power off, short-circuit the part to ground
to dissipate any residual charge which may be retained by a capacitor.
should be observed to try to localize the
12. General Instructions
fault to a particular circuit.
Troubleshooting at fourth and fifth echelon
(2) Operational tests. Operational tests
maintenance levels includes all the techniques
frequently indicate the general loca-
outlined for organizational maintenance (TM 11
tion of trouble. In many instances, the
662531612) and any special or additional
tests will help in determining the exact
techniques required to isolate a defective part.
nature of the fault. The equipment per-
The field and depot maintenance procedures are
formance checklist (TM 116625316
not complete in themselves but are supplemented
12) is a good operational test.
by the procedures described in TM 116625316
c. Isolation. The checks listed below will aid
12. The systematic troubleshooting procedure,
in isolating the trouble. After the trouble has
which begins with the checks that can be per-
been isolated to a particular circuit, isolate the
formed at an organizational level, must be com-
trouble within that circuit to a particular part.
pleted by means of additional localizing and iso-
lating techniques.
(1) Voltage and resistance measurements.
Use the schematic diagram (fig. 26) to
13. Organization of Troubleshooting
find the value of the components. Use
Procedures
voltage and resistance measurements
a. General. The first step in servicing a de-
the value for normal readings; com-
fective tube tester is to localize the fault to the
pare them with readings taken.
circuit responsible for abnormal operation. The
(2) Troubleshooting chart. The symptoms
second step is to isolate the fault to the defective
listed in the troubleshooting chart
part that is responsible for the abnormal condi-
tion. Some faults, such as a burned-out resistor,
to a component part.
can often be located by sight or smell. The
(3) Intermittent troubles. In all these tests,
majority of faults, however, must be localized
the possibility of intermittent troubles
by checking resistances.
should not be overlooked. If present,
h. Localization. The tube tester can be used to
this type of trouble may often be made
check pilot lamps, diode tubes, amplifier tubes
to appear by tapping or jarring the
for transconductance (G,,,), gas, and leakage
equipment. Check the wiring and con-
between tube elements, and to check tubes for
nections to the tube tester.
shorts. The first step in localizing troubles is to
determine the circuit or circuits at fault by the
14. Tools and Test Equipment Required
following methods:
The following chart lists the tools and test
( 1 ) Visual inspection. The purpose of vis-
equipment required for troubleshooting the tube
ual inspection is to locate faults with-
tester, the associated technical manuals, and the
out testing or measuring circuits. All
assigned common names.
meter readings and other visual signs
AGO 1428A
16
