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Post by tubefan on Jul 28, 2019 18:34:15 GMT -5
Picked up a mk3 that was sent to Barkett 2 years ago. I can see new hv caps and cans. Radio worked great for a short bit. Then I noticed while listening to DX the receiver starts to overload and distort on any strong signals. The guys on 6 are so strong that the audio almost mutes and I can hear a little crunch sounding audio. Distant signals seem to sound ok. If I listen to a distant signal and pull the AGC it seems to be working . Any tips where to start trouble shooting?
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Post by 2600 on Jul 28, 2019 18:58:21 GMT -5
Behavior of the S-meter is a significant clue when this happens. More to the point, how its behavior changes from when the receiver was working properly.
If you have a spare set of three 6BA6 tubes, I would switch them first and see what changes, if anything.
A radio that worked okay, and then starts to acquire a "personality" suggests a gassy tube. Or more than one.
Maybe.
73
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Post by tubefan on Jul 28, 2019 19:12:01 GMT -5
S meter seems to be normal. Just the high signals are over loading. I will try all new tubes tomorrow and report back. Thanks
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Post by tubefan on Jul 30, 2019 21:56:17 GMT -5
You nailed it ! This receiver had NOS 5749s in it. I replaced one at a time with known good 6ba6 out of a good working receiver and the middle one fixed it. With the 5749 tube listening to the guys on ch6 who are all almost pegging the needle in about 3 min of warm up the overloading starts. Replacing the middle with the good 6ba6 I let it run for 40 min on ch6 and all clear as day. Thank you for the tip. Now to start a new thread on a mk3 tx question.
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