TM 5-683/NAVFAC MO-116/AFJMAN 32-1083
arcing occurs, or if the brushes are badly worn,
7-1. Solid-state maintenance.
replacement is recommended.
Electronic system maintenance is required for
(2) Input and output. Input and output signal
proper operation. Specific maintenance procedures
voltages, which can be considered important indica-
should be obtained from the equipment manufact-
tors of operating conditions, should be checked on
urer. Preventing the solid-state component from
the regulator or function panels. A high input im-
failing will increase the electronic system's avail-
pedance voltmeter should be used for these mea-
ability. Preventive maintenance applied to elec-
surements. The checks should be performed every
tronic systems should be directed toward minimiz-
12-18 months. Data should be recorded for future
ing the chance of component failures thereby
reference and the test points where the data was
reducing the causes of system failure. There are two
taken should be fully explained.
primary causes of solid-state component failure.
(3) Semiconductor-controlled rectifier (SCR).
First is heat caused by overloading, surface con-
Spot check operation of SCR's by observing their
tamination or poor ventilation. The second is vibra-
neon lamp monitors. All lamps should either glow or
tion caused by mechanical stress, shock, moisture
not glow as a group. When lighted, all lamps should
due to environment, overvoltage, electrical spikes
glow with about the same intensity with one elec-
or static discharge while handling components.
trode in each lamp glowing somewhat more brightly
than the other.
a. Preventive measures. The following are general
(4) Planned outages. For planned outages, the
preventive measures applicable to individual equip
following maintenance should be performed:
ment within a system. Detailed preventive mainte-
(a) General cleaning with either low pres-
nance of specific solid-state components is covered
sure, dry air and/or a vacuum cleaner. Any air in-
later in this chapter.
take filters should be inspected, cleaned if possible,
(1) Keep equipment clean. Limit overheating
or replaced at this time.
and the chances of current leakages or flashover by
(b) Check all brushes, small auxilliary mo-
periodic vacuuming or blowing out dirt, dust, and
tors, variable slide-wire resistors (rheostats), poten-
other surface contaminants from the equipment en-
tiometers, and variable transformers.
closures. Use a non-conducting nozzle on the
(c) Inspect all control and power relays for
vacuum or air hose (a metal nozzle can cause com-
freedom of operation and the condition of their con-
ponent damage and/or breakdown). Do not use high
tacts. Also, check for failed surge suppression de-
pressure air, it may damage components.
vices when these are provided across the operating
(2) Keep equipment dry. Space heaters will pre-
vent the accumulation of moisture and subsequent
(d) Check for any loose connections or evi-
corrosion thereby limiting intermittent component
dence of heating on large cable, bus, and large
SCR's or rectifiers. Correct cause when found.
(3) Keep equipment tight. Tight connections
(e) Check SCR or rectifier legs and corre-
and secure leads and contacts limit adverse effects
sponding fuses with an ohmmeter. Test all elements
of parallel groups individually.
(4) Keep equipment cool. Proper ventilation
limits overheating due to high ambient tempera-
7-2. Solid-state components.
Maintenance procedures for solid-state component
b. System checks. The following are basic system
are designed to detect evidence of abnormal heat-
checks which may be applicable to components and
ing, moisture, dust and other contaminants; pro-
subassemblies within a given system.
mote good reliability and minimize downtime; pro-
(1) Magnetic device. Check the operation of
long the useful life of the equipment; and, recognize
magnetic and contact-making devices in accordance
repeated component failures and take corrective ac-
with applicable instructions. Brushes in motors
(used for all motor driven position adjusters, etc.)
a. Static testing. For this work, static testing is
and all exposed brushes or contact buttons for
rheostats, potentiometers, and variable transform-
taken to mean one or more electrical tests, per-
ers should be inspected every 12-18 months. For
formed on a given component, using very low volt-
frequent operations or adverse operating conditions,
ages or powers. Furthermore, these tests are de-
such as very dusty, humid, and corrosive areas, in-
signed to give a very general idea as to the
spections may have to be done every 4-6 months. If
component's overall condition and not its perfor-