Table 3-4 Cross Reference To Module/Component Assemblies
Needing Repair Materials-Continued
REPA1R PROCEDURE AND COMPONENT PARTS
POWER CAPACITORS AND DRIVER MODULE A4 (fig. 3-13)
Resistors R424 and R425 are secured with a fillet of Epocast
202 (101 parts of 202).
Plate SP04B-112B24 is secured across transformer T402
core with Eocast 202 (100 parts of 202).
COMPONENT ASSEMBLY A4A1 (fig. 3-14)
a. Transistors, Q400 through Q411 are secured with Epocast
202 (100 parts of 202).
A4A1 is conformal coated with 1B31 (Humiseal), both sides.
COMPONENT ASSEMBLY A4A1 (fig. 3-16)
Capacitors C51l and C513 are secured with a fillet of
Epocast 202 (100 parts of 202).
b. A5A1 is conformal coated with 1B31 (Humiseal).
LOGIC COMPONENT ASSEMBLY A6 (fig. 3-17)
A6 component assembly is conformal coated with 1B31
(Humiseal), both sides.
BOOST REGULATOR COMPONENT ASSEMBLY A7
A7 component assembly is conformal coated with 1B31
(Humiseal), both sides.
the above is evident, perform repair procedure
3-17. Nonformal Coating with 1B31 (Humiseal)
The following procedure shall apply to the
g. After all areas are repaired, the board can be
replacement of a comformal coated component
reinstalled in its permanent position.
mounted on either a module or component
3-18. Use of Epocast 202
To accomplish repair of the components which are
Do not use 1B31 and Tuluol/Toluene in
held with Epocast 202, proceed as follows.
presence of open flame or sparks. Avoid
inhalation of vapors. Adequate ven-
Required mix of either 100 parts or
tilation to the outdoors is necessary.
60 parts of resin 202 is specified in table
Prevent contact with eyes and skin. If
contact occurs, wash with soap and
a. Preparation of Epocast 202. Combine 100 parts
by weight of hardener 9615 with 60 or 100 parts by
a. Dissolve existing 1B31 from small rework area
weight of resin 202 and stir thoroughly until a
with isopropyl alcohol and cotton swab stick.
uniform color is obtained. Mix only quantities which
b. Replace the defective part using good work-
will be used within 2-1/2 hours. If not used within
2-1/2 hours, discard mixed material.
c. Replace the conformal coating with Type 1B31
b. Repair Using Epocast 202.
used full strength from its container. Shelf life of
1B31 in the container is six months at room tem-
perature. 1B31 maybe thinned with Tuluol/Toluene
Use care in heating Epocast 202 not
to damage nearby components. Use
to adjust thickness, if necessary. Expose only
either 50 watt max soldering iron or heat
quantities of 1B31 to the atmosphere that will be
used within 1-1/2 hours. Any material that has been
gun, whatever will cause the least heating
exposed 1-1/2 hours, or more, shall be scrapped.
Material shall be stored at room temperature, away
(1) Heat area of Epocast 202 with 50 watt max
from excessive heat.
soldering iron or heat gun until material is soft. Lift
d. Apply a thin coat of conformal coating to the
small component away from material. While still
affected area, overlapping the existing coat about
soft, remove material using a non-metallic tool.
1/16 of an inch to obtain a moisture seal. A short
artist brush will serve as an applicator.
with soft brush and isopropyl alcohol.
e. Allow ten minutes air drying before handling.
(2) When a fillet bond is required, apply fillet
Apply heat by means of an infra-red heat lamp,
along the length of component. A thin layer of
forced-air heat gun or cure in oven. Object is to
adhesive may blend over a portion of the body of the
increase the surface temperature of the coated area
component. When components must be en-
to 170°F ±5°F for one hour.
capsulated, apply adhesive (5 to 20 mils thick) over
f. After the application and cure of conformal
the entire mounting surface of the components.
coating, inspect repair area for any blistering,
(3) Cure adhesive for two to four hours at 150
wrinkling, cracking or peeling of coating. If any of
±10°F or for 24 hours at room temperature. Clamp