{Collins} Oscillation on 30L-1

Hello everyone.

I am fixing a 30L-1 for the Club which was out of service and that we do not know the history behind it. It has 811 tubes that are mid-life but the four measure the same. I replaced the original power supply with the replacement kit found online. No problem with that. I also replaced the chokes on the plates of the tubes that were overheated and their resistors cracked.

First tests went fine but suddenly, in the 20m band, when keyed down, an oscillation was trigged drawing about 1 amp on the plate current and overheating the new chokes.

I have seen this behavior before in other units but they were repaired by other people. I also heard that there is some “fix” for that or, a reason for that to happen.

Al tests were performed on a dummy load.

I’ll appreciate help.

Thank you for your time,


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