Tram D201 microphonic v502 tube

[klj2497]

I noticed on ssb receive that i am getting what sounds like feedback i can hear myself tapping on the receive board and the bal mod. board it is the loudest when i tap v502, and t502. I have replaced the r520 recently when the ssb receive quit and got it running again. I swapped out tubes, no change and i am going to check the tube voltage again. and test components when my pain subsides. im having a bad day today.

 

[Shockwave]

There is a lot of gain in the V-502 stage and even a good tube will make noise when tapped on SSB. If the tube is microphonic enough to produce feedback, that is an issue. Many of the last batches of 6GH8A tubes manufactured were junk. I've noticed some of the ones labeled GE will oscillate in some stages because they have more gain than normal...for a little while. Try a different brand for V-502, not just a different tube.

 

[nomadradio]

Yeah, there will always be some microphonic behavior from V502. No easy way around it but to see which of the five 6GH8 tubes in the radio makes the least noise installed in that socket. Odds are they won't all be the same.

This is one performance detail a tube tester won't tell you about.

73

 

[klj2497]

Thatts very interesting, as they say on laugh in. I will do some swapping around. I also noticed when i put my hand on the top of the radio or plug in and touch the d104 the static quiets down and the meter goes down. its doing it in am and ssb.

 

[Shadetree Mechanic]

Thatts very interesting, as they say on laugh in. I will do some swapping around. I also noticed when i put my hand on the top of the radio or plug in and touch the d104 the static quiets down and the meter goes down. its doing it in am and ssb.

Do you have your station ground connected to the chassis of the radio?

 

[klj2497]

No, I dont have a station ground. but thats a good idea im going to read how to. I have my 5/8 wave antenna grounded.