The AM Forum

I have a Gates BC1-T that I use on 75 meters.  Lately it has started to distort the audio along with a decrease in signal strength.   I have rebuilt the audio section and the rf driver section but nothing seems to stop the problem from occuring.  When I first turn it on everything is fine for about 10 minutes and then it will start distorting during a transmission and will continue to do so during any subsequent transmission.
I have replaced all tubes, resistors and capacitors, but nothing seems to solve the problem.  Any ideas, anyone?

disconnect the wire on the electrostatic shield on the mod transformer to verify that the shields are not shorting to the secondary...I had a problem similar to yours and that was the case...I left the shield wire disconnected and the transformer worked ok..gud luk   Steve

It could be worn contractors. I had a BC-1G in broadcast use that would run fine for hours after being off then fail (usually at 4 am). Eventually the contacts get pitted and start to heat from the damaged surfaces.

Unfortunately, there are several contractor assemblies and each one is comprised of tiny parts and springs. On the plus side, you don’t have to work on it at 4 am.

Yep, worn 'contractors' can screw up any job... ;)

73DG

Spellcheckers attempt to protect us from making spelling errors and this happens.
Hey Apple! "Contactor" is a legitimate word!  Sheesh.

You might check the disc cap on the tube mounting bar.

I had that fail gradually, was tough to find.

73DG

too-fresh a contractor can also screw up any job...

Finally found it!  My exciter was failing, changed it and now it works fine.  Thanks for the replies.