model 20 radio tubes. - Printable Version

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model 20 radio tubes. - joesdad49 - 03-31-2011

What is the purpose of the 71A tubes. One of mine burnt out but, the radio still works. The sound is staticy(sp?)
Could this be because of the burnt tube? I did ground one of the capasitors with my finger to the ground on the chassis and the sound came clear.
But, the volume would reach a certain point then not go any higher. Any ideas?
I look forward to the answers. I'm definately puzzled. :

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Re: model 20 radio tubes. - exray - 03-31-2011

I can't vouch for the static part but the Model 20 uses a pair of 71As in a push-pull configuration for the audio output. What that means is that each tube works individually on each half of the audio cycle. So yes, with one removed (or defective) the audio will not reach maximum power and is likely to sound a bit distorted.

-Bill

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