Slide back the cover on the spare tube compartment. Use the tube puller to
remove the spare tube.
The new tube is installed by pressing the cathode end into the tube socket.
Check to see that the tube is firmly seated in the contact ring.
Replace and secure the air baffle assembly.
After the new tube is installed, you must use a multimeter to determine if any filament voltage or
cathode current adjustments are required. By performing the following steps, these adjustments
can be checked and made. This procedure pertains to BAND I operation only.
With the RF head still removed from the transmitter case, connect the RF head
to the transmitter case with Electrical Cable CX-10879/GRC-103(V) shown in
Connect the dummy load to the PWR OUT connector on the front panel of the
RF head. Damage to the equipment will result if this is not done.
When the transmitter RF head is extended, it no longer receives the necessary cooling
provided by the centrifugal fan. Therefore a cooling fan must be pointed toward the
power amplifier tubes if the transmitter RF head is operated for more than 5 minutes.
Turn the transmitter ON. Tune the transmitter as per the tuning procedure in
Refer to View B of Fold-Out 14 while reading Steps 4 thru 10.
Open the cover plate over the test points and adjustment potentiometers on the
transmitter RF head. These points are located in the same area as the elapsed
time indicator. The potentiometers are labeled R1 thru R4.
Set the multimeter for the 10-volt d-c range. Next connect the positive meter
probe to TP1 and the negative meter probe to TP2.