6SN7 tube static

[belgianbrain]

Ordered a pair of RCA 5692 tubes for my Schiit Freya that test close to NOS (according to seller's test results).

One of them is static. Sometimes intermittent. I've tried cleaning pins and letting it burn in for a few hours. Problem decreases when it is hot, but is still intermittent, and is back full force when tube is cold.

If I swap L/R channels, problem migrates channels. Is there a common cause of this in tubes, or is the tube just bad?

 

[mroboto]

Bad connection inside the glass envelope probably, got the same problem with a Sylvania 6SN7GT, resoldered the tips of the pins with no luck.

Emission tester meter needle jumps sudently to Good after warm up, then goes off, is intermitent too.

 

[primosounds]

Tube maybe gassy which makes it test high but in actuality is on its last legs. Tubes that are also on their way out will tend to be noisy as well. Try to get a refund or another tube.

 

[sKiZo]

You mentioned cleaning, but did you also re-tension the sockets? All pins aren't created equal, and a smaller pin could give you the same symptoms you describe ...

 

[heyraz]

Sounds like a faulty tube, plain and simple.
Maybe the damage occurred during shipment, although I find that odd for a military tube (5692 is a mil. tube).
If possible, I'd contact the seller.

 

[belgianbrain]

Yep, I've messed around with this tube a lot and it's simply static city. Seller guaranteed refunds if not satisfied, so I've requested a return.

I've not had such a problem with any other tube in this unit. Too bad. I paid a lot of money and waited quite awhile to get this pair.

 

[TT-newbie]

I had similar experiences. I had several 6SN7 crackling in my Cayin mono-block. They would produce loud crackling sound within a minute once I turned on the unit, then it would work fine afterward. This problem has baffled me for years, I have now over 5-6 pieces of various bad 6SN7s. I never figure out what problem is. 6SN7 used to be very cheap tubes. However, there days they are getting very expensive.

 

[belgianbrain]

I'm going to evaluate a platinum matched quad of Tung-Sol new issue 6SN7GTB soon to see if it is possible to ignore NOS in the future.

 

[maxhifi]

Some tubes are just noisy and bad. I've had a few like that too. Not sure what's the root cause, but the solution is clear - use another tube. 6SN7 is a very very common tube, I wouldn't abandon the idea of finding good NOS, just because of one dud.