Potomac Instruments FIM-21 - Integrated Circuit Replacement; Preventive Maintenance Tips

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SECTION 4. MAINTENANCE (Cont.)
4 .5 To Remove FIM from Case (Cont. )
3. Place unit upright on bench with cover away from you;
remove the cover-panel assembly from the case by push-
ing with the thumbs against the cover hinge while grip -
ping the case. This assambly will stand upright by
itself, but should have support under the dial end of
the chassis for safety.
4. Unplug the battery connector (on top of chassis) to
separate the two parts completely.
4.6 To Operate the FlM With Case Removed
The Flli may be operated by connecting the battery connector and
opening the cover so as to close the interlock microswitch. It may be placed
upright, with support under the chassis near the dial. For access to the cir-
cuit boards, it may be operated while resting on the end nearest the dial.
IC Replacement
It takes considerable force to extract an IC from its socket. It
rrrust be pried out by inserting a tool between the IC body and socket, or pulled
out by means of a tool made for the purpose. Do not use an adjacent component
as a fulcrum f'or prying. Because of the possibility of damaging an IC when re-
moving it, do not remove it unless circuit checks show it to be defective .
(See t
roubleshoo ting voltage charts, Figure 4-1.)
To install a new IC, first be sure that all pins fall in the center
of their socket holes without forcing. In new ICls, each row of pi ns must
usually be bent toward the other to achieve this. They can be bent by pressing
each row of pins against a fiat surface, or by use of suitable pliers, bending
the pin s as close to the body as possible. When the pins f'it the socket, place
the notched end of the IC at the notched end of the socket and press gently into
place.
4.8 Preventive Maintenance
To m aintain the FIM-21 and FIM -41 in good condition, regular cleaning
and inspection is required at intervals depending on local conditions. If the
unit is used frequently in dusty areas or rough country, more frequent checks
are required. It should be cleaned and inspected after any extended period of
hard use.
R emove all dust and dirt from the unit, using a damp cloth or sponge
all over, and using a brush to remove dirt from crevices.
Clean the dial window and m eter glass only with water and a mild
detergent on a clean cloth. Do not use strong solven ts J which can do much
damage.
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