for the aircraft and component. Corrosion control
easier. Most test racks have plug-in extensions that
of generators is the same as for motors /inserters.
let you raise the module so all parts are accessible
Generators are not likely to be overloaded. A
for test and repair. The module is not expendable,
but it is easy to repair, since all parts are of
defective load (one that is highly inductive, and
not the equivalent of resistance load) may result
conventional design. Miniature and subminiature
parts are so common in today's electronic equip-
in low voltage, excessive field current, over
saturation, and continued low voltage. Any
ment that they are considered to be conventional.
condition resulting in abnormal field current may
PRINTED CIRCUIT MAINTENANCE
result in overheating. This condition is dangerous
to the affected generator and the entire system,
dc as well as ac.
Although troubleshooting procedures for
printed circuits are similar to those for con-
ventional circuits, repair of printed circuits
PRINTED CIRCUITS
requires considerably more skill and patience.
According to OPNAVINST 4790.2, only AIMDs
Learning Objective: Identify character-
being certified as having the capability may
perform microminiature circuit repair. Activity
istics of printed circuits, including modules
certification means that the AIMD has in-
and potted components, and recognize
dividually certified technicians assigned and
circuit construction features.
NAVAIR approved, operable repair equipment
The move toward replaceable units has lead
available, and does not include any specific
to several new methods of electronic equipment
authorization to repair.
Initial repair technician certification is granted
construction. The printed circuit is an example of
only upon successful completion of the appro-
this construction. This design or type of circuit
priate NAMTRAGRUDET course or equivalent
gives speed and economy to maintenance, as well
contractor training course, approved and provided
as saving space and weight.
by NAVAIR. Each individual must be recertified
periodically to assure continued quality of
CIRCUIT CONSTRUCTION
performance.
Photoetching is one method used to manu-
facture printed circuits. In this method, a plastic
or phenolic sheet with a thin layer of copper
REVIEW SUBSET NUMBER 6
coating is used. The copper coating is covered with
a light-sensitive enamel and a template of the
Q1. List the manuals to which you should refer
circuit that appears when the sheet is exposed to
for the correct cleaning agents and proce-
light. The entire sheet is then exposed to light. The
dures.
exposed area of copper reacts to the light. An
etching process then removes this area. The
exposure of the printed circuit is similar to a
photographic exposure. The enamel on the
Q2. For a technician to repair a printed circuit
unexposed circuit protects the copper from the
board, what certification must he/she meet?
etching bath that removes the exposed copper.
After the etching bath, the enamel is removed
from the printed circuit. This leaves the surface
ready for soldering parts and connections.
TEST EQUIPMENT
Some manufacturers use machinery to mount
standard parts like capacitors, resistors, and
Learning Objective: Identify functions,
transistors--further speeding manufacture. Cir-
capabilities, and operating characteristics
cuits produced by this method operate as well as
of various types of aircraft test equipment.
conventional circuits and are easy to repair.
Look at figure 2-25. From the troubleshooters'
You can classify test equipment as either
standpoint, it shows an improved type of
common or peculiar. In some cases, test equip-
construction that consists of a removable modular
ment may be peculiar to a specific system, but that
subassembly. The modules have numerous internal
system may be used on several different aircraft.
and external test points to make troubleshooting
