I performed what seemed to be a rather odd repair on an older Command Tech
VHF-2000. I thought I would share this since it could possibly affect the HF
models. This particular amp like most has a piece of coax that comes off the
output of the tank circuit and goes over to the antenna relay. In this case a
harmonic filter. The coax was affixed to the side of the wall and dove down to
the bottom and over to the relay. Filter in this case. There was what seemed
to be a soft arc to the coax as it bent over the edge and down. The amp
exhibited no output whatsoever and acted like there was not antenna connected.
I tracked down the problem to that coax being internally shorted. An autopsy
of the piece of coax was amazing. Apparently the owner of this amp operated
digital modes like JT65 so I would think there were many periods of heavy duty
cycles. Apparently over time the dielectric center conductor heated up and
little by little the wire migrated to the outer edge and e
ventually broke through at the "arc" strain point and shorted to the braid.
Several inches of the center wire was way far away from the center of the
dielectric. Go figure.
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|