TM 11-6625-298014
TROUBLESHOOTING AIDS
Introduction
The following is provided to augment information
contained elsewhere in this and other TM 500 Series
family manuals when troubleshooting becomes
necessary.
Circuit Descriptions
Each manual has a section devoted to explaining
circuit operating theory. Used conjointly with the
schematics, this can be a powerful analytic tool.
Diagrams
Block diagrams and detailed circuit schematics are
located on foldout pages in the service section of most
of the TM 500 Series family manuals. The schematic
diagrams show the component values and assigned
circuit reference numbers of each part necessary to the
circuit design. Usually the first page of the service
sections defines the circuit symbols and reference
designators used in that particular instrument. Major
circuits are usually identifiable by a series of component
numbers. Important wave-forms and voltages may be
shown within the diagrams or on adjoining aprons.
Those portions of the circuits located on circuit boards
are enclosed with a blue tint outline.
Cam Switch Charts
Cam switches shown on the diagrams are coded on
comprehensive charts to locate the cam number of the
switch contact in the complete switch assembly,
counting from the front, or knob end, toward the rear of
the switch. The charts also indicate with a solid dot
when each contact is closed.
Circuit Board Illustrations
Line illustrations showing component locations
keyed with a grid scheme for each circuit board are
usually placed on the back of a foldout page and
sequenced as close as possible to an associated
schematic. The GRID LOC column in the Electrical
Parts Lists keys each component to the Location
illustrations.
Component and Wiring Color Codes
Colored stripes or dots on electrical components
signify electrical values, tolerances, etc., according to
EIA standards. Components not color-coded usually
have information printed on the body. The wiring coding
follows the same EIA standards.
Testing Equipment
Generally, a wide-band oscilloscope, a probe, and a
multimeter are all that is needed to perform basic
waveform and voltage checks for diagnostic purposes.
The calibration procedures in the manual for each plug-
in module list specific test equipment and the features
necessary to adequately check out that particular
module.
TROUBLESHOOTING TECHNIQUES
Introduction
This troubleshooting procedure is arranged in an -
order which checks the simple trouble possibilities
before proceeding to extensive troubleshooting.
Control Settings
Incorrect control settings can indicate a trouble that does
not exist. If there is any question about the correct
function or operation of any control, see the Operating
Instructions section of the manual for the instrument
involved.
System and Associated Equipment
Before proceeding with troubleshooting the TM 500
Series system, check that the instruments in the system
are operating correctly. Check for proper interconnection
between the power module and the plug-in modules.
Check the line voltage at the power source. Check that
the signal if properly connected and that the
interconnecting cables and the signal source are not
defective.
The associated plug-in modules can be checked for
proper operation quickly by substituting other like units
A-8
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