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 How to track down distortion

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aropper



Posts : 1
Join date : 2010-10-13

PostSubject: How to track down distortion   Sun Oct 17, 2010 10:34 am

I have recapped a simple RCA 6D030 and the audio is distorted with a scratchy slight hum on stations. The plate voltages on the RF and IF are about 10V high but otherwise seem OK. It does not sound like a cone problem and the speaker moves freely. I replaced the 35L6 with one I know is good in another set. How does one start to run down this kind of problem (wihtout an oscilliscope)?
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Johnnysan



Posts : 64
Join date : 2010-10-12

PostSubject: Re: How to track down distortion   Sun Oct 17, 2010 3:01 pm

Many distortion problems occur in the audio detector stage; check voltages and resistors there.
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pixellany



Posts : 58
Join date : 2010-10-12

PostSubject: Re: How to track down distortion   Sun Oct 17, 2010 3:01 pm

Lots of things to check...

First, is the distortion similar on all stations? If it happens more on strong stations, there may be an AGC issue.

Can you substitute ALL of the tubes?

Can you try a different speaker and/or output transformer?

Any chance that there is a wiring error afer re-capping? (Was it working before?)
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Chas

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Posts : 33
Join date : 2010-10-12
Age : 70
Location : S. Dartmouth MA 02748-1225 ------------ Avatar: Uncle Tony's Shack

PostSubject: Re: How to track down distortion   Sun Oct 17, 2010 3:35 pm

Quote :
Lots of things to check...
First, is the distortion similar on all stations? If it happens more on strong stations, there may be an AGC issue.
Can you substitute ALL of the tubes?
Can you try a different speaker and/or output transformer?
Any chance that there is a wiring error after re-capping? (Was it working before?)

All above is very good advice.

If you can readily remove the speaker, do so. Support the basket of the speaker in the right hand, bring the palm of the left hand smartly up against the magnet assembly, so as to thump the speaker. If you hear a low smooth resonance, the speaker is O.K. If you hear a sort of a "goosh" sound the voice coil is rubbing. Other hidden speaker faults are partially unglued spider and the rim of the surround as well as loose voice coil windings.
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