05-12-2020, 12:17 PM
Eric,
It could be a tube/valve problem of some kind, or just an intermittent contact - dirty pins or socket.
If I read correctly, you are getting a clean RF signal through the IF, but the noise appears to be generated after (or at) the detector (12SQ7). You could try disconnecting the volume control (centre lead) or just insert a plug into the phono jack. Make sure that jack has clean contacts too, as it could be a source of trouble. These tests tell if the noise is generated only in either the triode section of the 12SQ7 or the output tube. This would determine if the problem was in the audio system. Likewise, temporarily disconnect the IF transformer from the detector tube.
Hope that helps,
Ed
It could be a tube/valve problem of some kind, or just an intermittent contact - dirty pins or socket.
If I read correctly, you are getting a clean RF signal through the IF, but the noise appears to be generated after (or at) the detector (12SQ7). You could try disconnecting the volume control (centre lead) or just insert a plug into the phono jack. Make sure that jack has clean contacts too, as it could be a source of trouble. These tests tell if the noise is generated only in either the triode section of the 12SQ7 or the output tube. This would determine if the problem was in the audio system. Likewise, temporarily disconnect the IF transformer from the detector tube.
Hope that helps,
Ed
I don't hold with furniture that talks.
