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Maintenance of the FN- 20B should consist of periodic checking
of tubes,
cleaning, visual inspection and lubrication where
required.
The use of air filters materially assist in keeping
the transmitter interior clean;
however,
often periodical re-
moving of dust will still be necessary.
Since electrostatic
fields create " dust catchers",
attention should be paid to
these places.
Support insulators in the tank are probably the
worse offenders.
They must be kept clean and free of all
foreign material at all times.
Not to do so may result in
arcing and shuttering of the insulators.
Particular care must be taken to remove dust from the high
voltage feed through capacitors in the amplifier.
These
capacitors should be cleaned both inside and outside of the
amplifier enclosure.
This part is probably the most critical
in the high voltage wiring because of its nature to attract
small particles of dust.
The teflon deck which acts as an air chimney for the tubes,
should also be wiped clean.
The underside of this deck should also be kept clean.
The
removal of the tubes will be necessary for this operation.
When inspection of air filters discloses dirt or foreign ma-
terial,
they should be disca
.
L ded and replaced with new ones.
The type of filter used in the FM-20Bis a disposable type filte_
and may be replaced at most any local hardware or heating
supply store.
Once a month the entire transmitter should be cleaned of dust.
In the same case of the power amplifier,
open the back door of
the enclosure and thoroughly wipe it clean of dust after check-
ing for HV present.
In the case of the driver amplifier,
the
back door is removed by loosening six Lion fasteners,
the in-
terior of this amplifier should also be wiped clean of dust.
The protective relays should have the dust cleaned out as
required and contacts burnished with a burnishing tool.
Those
relays are protected with dust covers and are telephone type
relays and should require little attention.
The contact areas of the shorting bar in the plate line assem-
bly should be lubricated occasionally with a silicon base
lubricant.
This will make for easier tuning and reduced wear.
The moving parts in amplifier should also be lubricated for
the same reason.
The bearings for the blower of the motor for the 2.à.
are
sealed bearing3 normally giving long trouble free operation.
6/22/61
-20-
FM- 20B
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