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RE: Sounds like you had a grounding glitch; loose connection...

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In Reply to: RE: Sounds like you had a grounding glitch; loose connection... posted by 40492 on August 24, 2014 at 18:23:40

Follow-up:

I replaced the GE 6550 tubes with the stock KT-88-98 tubes (as thought that one of the GE tubes might be the culprit).

Nope. There was the same buzz, and I started to think about faulty caps or resistors, but decided to replace vintage Sylvania VT-231 tubes with the stock Chinese tubes, and it was OK.

So, one of Sylvania VT-231 tubes was to blame.
It is interesting that I purchased them as NOS from a reputable dealer and barely used them. Is it possible that a tube may spontaneously loos vacuum? I don't have a tester to check it.

Now the amp sounds nice (warm, moderately colored and consistent) but it has lost some magic and subtle detail that were present with vinatge tubes.
Will try the GE6550 tubes again.

Follow Ups:

RE: Sounds like you had a grounding glitch; loose connection... - Michael Samra 14:18:50 09/08/14 (0)
The old vintage tubes develop oxidation on the pins or sometimes especially on 6SN7 types the tube's pins need to be heated up and solder reflowed..I did this on two of my 6SN7 TungSol round plates and they have been superb ever since. You may just need just need to clean the tube pins with some tuner cleaner or alcohol even but look at the bottom of the tube pins and see if the solder joints look corroded.

Honest amplification is better than excessive 2nd order distortion anytime.
noisy VT-231 on fire-up - FenderLover 06:57:07 09/08/14 (0)
Almost sounds like the power supply maybe at issue and is causing a sensitive tube to manifest noise on fire-up. Can you try those Sylvania VT-231 in another amp, to rule-out the tube being the sole issue?
RE: Sounds like you had a grounding glitch; loose connection... - mhardyman 06:12:59 08/26/14 (0)
"So, one of Sylvania VT-231 tubes was to blame.
It is interesting that I purchased them as NOS from a reputable dealer and barely used them. Is it possible that a tube may spontaneously loos vacuum? I don't have a tester to check it."

If vacuum had been lost then the getter flash would be a cloudy white. If it still looks like a mirror then the only way is to test it.

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