[TenTec] TT 1220 problem

[Bwana Bob]

Brian:

In addition to caps, check the final tuning and antenna SWR. My 1220 was
emitting a motorboating sound when I used certain mobile antennas. The
problem could be a parasitic oscillation in the final. Does it whine in
the low power position as well? Try adding additional grounds to the
final amp board. Try tweaking the final tuning cap. Years ago, we used
to tune 2 meter transmitters while listening to a cheap FM radio tuned
to a quiet spot on the dial and tuning the transmitter for minimum hash!

		73,

		Bob WB2VUF

Brian Haren wrote:
> 
> Hello All!
> 
> I have a 1220 2-meter kit that has an 'issue' I hope someone can help me with...
> 
> The kit was built by a local ham with a lot of kit-building experience and was recently received back from TT where they replaced a few switching diodes, checked functionality and gave it a clean bill of health.  I bought it from the original owner and a good friend.  According to him it has less than 2 hours operating time on it.
> 
> The radio emits a constant low-level high pitched whine.  It's not a 60 hz 'hum', it's much higher frequency whine.  It can be heard by receiving stations behind my audio and I also pick it up through the radio speaker while receiving other stations.  I ran a number of tests today, to include turning off all appliances, lights and power supplies in the house and running the radio from a battery.  The whine persists.  The interesting thing is that other stations report the whine fades during long transmissions, but always returns after unkeying and beginning another transmission.  One local ham stated that it sounded like some of the capacitors had not yet formed and might well go away with time.  I'm not so sure.
> 
> Does anyone have experience with this radio and perhaps have experienced the same problem?  I'd love to get this problem solved without having to return it to TT.  Thanks in advance!
> 
> Brian
> W8BYH
> _______________________________________________
> TenTec mailing list
> TenTec at contesting.com
> http://lists.contesting.com/mailman/listinfo/tentec