01 March 2005
5-4.3.1. Fungus-Proof Varnish. The authorized
f u n g u s p r o o f coating is Varnish, ASTM D 3 9 5 5
(15) Windows or lenses.
may be thinned with Thinner, A-A-3007 (Volume IV or
(16) Transparent plastic parts.
5-4.3.2. Items to be Protected Against Varnish
(17) Plastic materials such as polyethylene,
Application. Varnish shall not be applied to any surface
polystyrene, polyamide, acrylic, silicone, epoxy (other
where it interferes with the operation/performance of
than printed wiring boards) melamine-fiber-glass,
the equipment. Such surfaces shall be protected against
fluorocarbon, vinyl, and alkyd.
varnish application by masking with Pressure Sensitive
Tape, SAE-AMS-T-22085 Type II (Volume IV or V,
(18) Materials used for their specific arcresistant
properties and classified as such.
a. Components and Materials.
b. Electrical contacts, contact portions, or mating
surfaces of binding posts. Also connectors, fuses, jacks,
(1) Cable, wire, braids, and jackets that are
keys, plugs, and relay sockets (including tube sockets,
flexed during operation of the equipment.
switches and test points).
(2) Cables where treatment would reduce the
c. Mechanical parts.
insulation resistance below, or increase the loss factor
above, the acceptable values. These values are specified
(1) Bearing surfaces (including bearing surfaces
in the applicable service directives.
of gaskets and sliding surfaces).
(3) Variable capacitors (air, ceramic, or mica
(2) Gear teeth and gear trains or assemblies.
Pivots and pivot portions of hinges, locks,
(4) High wattage and wirewound resistors.
(4) Screw threads and screw adjustments (those
operating voltage of over 600 volts and in danger of
moved in the process of operation or adjustment).
(5) Springs, except at base of pile-up.
(6) Painted, lacquered, or varnished surfaces,
unless otherwise specified.
d. Surfaces which rub together for electrical or
magnetic contact. For example, bearings, contact
(7) R o t a t i n g parts such as dynamotors,
fingers, potentiometers, shafts, shields, and variable
g e n e r a t o r s , and motors. However, electronic
components associated with these parts shall be treated
in accordance with procedures outlined in this manual.
e. Surfaces whose operational temperatures exceed
266°F (130°C) or whose operating temperatures will
(8) Waveguides (working surfaces).
cause carbonization or smoking.
(9) Electron tubes.
f. The exterior or visible outside portion of indicating
instruments (do not open or treat inside), control boxes,
(10) Tube clamps
or equipment that are mounted in the cockpits of
(11) Miniature tube shields.
5-4.3.3. Methods of Application. The varnish coating
shall be applied by spraying, brushing, dipping, or any
combination. The dried film shall have a clear, smooth
(13) Pressure-contact grounds.