(1) The first item to be checked during a monthly PM is the transmitter. To perform
this check you must remove the transmitter RF head and transmitter fixed head from the case.
Four captive screws must be loosened in each head to allow its removal. After removing both
transmitter heads, inspect the chassis and case interiors for corrosion, sand, dirt, and fungus.
Cleaning may be accomplished with a cloth and trichloroethane. Do not forget the previous
warning about highly toxic phosgene gas being produced when trichloroethane is exposed to an
open flame or hot metal.
(2) The second item to be inspected is the elapsed time indicator. The indicator is
located on the right side of the transmitter RF head. Therefore, this check should be made while
the RF head is out of the transmitter case. Open Fold-Out 14 and locate the elapsed time
indicator in View B of the Fold-Out.
When the elapsed time indicator shows 5000 hours or more, the transmitter tubes and the elapsed
time indicator should be changed. The scale on the indicator is divided into ten increments, each
one indicating 1,000 hours of running time. The transmitter tubes are located at the rear of the
transmitter RF head. Fold-Out 14, View A shows the location of the transmitter tubes.
A spare tube is stored in the RF head and access to this tube is gained by a sliding cover on the
top of the unit. Whenever a tube has been replaced with the spare tube provided, the transmitter
RF head should be aligned by higher category maintenance at the earliest possible date. Also a
new tube should be installed in the spare tube compartment. View A of Fold-Out 14 also shows
the location of the spare tube.
When a new transmitter tube is installed, the organizational repairman must check and adjust the
filament voltage and cathode current. The following steps should be followed when it becomes
necessary to replace a transmitter tube.
Remove the RF head from the transmitter case.
Refer to View A of Fold-Out 14 while reading Steps 2 thru 6.
Loosen the screw at each end of the air baffle assembly and remove the
Insert the tube puller prongs into the holes in the top of the defective tube and
pull the tube straight out.