Specifications

transmit, or vise-versa. The RX PIN diodes are much smaller, and have a greatly lower
power dissipation rating, so are easy to damage, with even a few hundred milli-watts of RF
power. If the amplifier is in a receive condition when the exciter goes into a transmit
condition, the RF can enter the RX PIN diodes, and burn them out, but there is an RX fuse
in-line with these diodes. If the fuse is burnt out, the exciter will not have good RX.
Replacing the fuse will usually fix the problem. A Hot-switch sensor will likely "trip" long
before the RX diodes will be damaged. An LED on the front panel will indicate that a "hot-
switch" condition exists. Stop using the amp at this time, and make the needed changes to
prevent this condition. Details in the user manual tell how to configure the exciter and amp
for proper keying sequence.
Since the PIN diodes in my 86 were beyond any repair, I decided to completely remove that
system, and install a vacuum relay T/R system. There are several web sites on the Internet,
which have this modification.
In fig.1 letter "A" points to the two vacuum relays and mounting hardware, of the modified
T/R system.
Fig.1