2a3 vacuum lost

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10-05-2018, 21:30
chris@panteg

2a3 vacuum lost

I think one of my 2a3's has lost it's vacuum, a milky white substance around the base, I think there is a tiny hole in the glass envelope around the base grid.

The filament does not glow, yet still appears to function, getting very warm/hot though not as hot as the other tubes.

I've noticed also the 2a3 next to it glows a bit brighter, could it be working harder to compensate for the other 2A3? Despite this it seems to be sounding just great, though possibly a slight imbalance but I'm not entirely sure.
11-05-2018, 08:24
snowman_al

Bad luck.
2A3s gettering, the silver flash, is normally at the base end. If it has turned milky that's a good sign of an air leak.

If that is the case, I would be surprised if it is actually working? (Push pull and parallel single ended amps will still work to a degree on one output valve.)
And I wouldn't use it any more.
11-05-2018, 09:16
chris@panteg

Quote:

Originally Posted by snowman_al

Bad luck.
2A3s gettering, the silver flash, is normally at the base end. If it has turned milky that's a good sign of an air leak.

If that is the case, I would be surprised if it is actually working? (Push pull and parallel single ended amps will still work to a degree on one output valve.)
And I wouldn't use it any more.

Thanks, yes I've replaced the pair yesterday, thing is I couldn't find out much info on the net so thought I would post on here for some sort of reference.

No question about it, it was still working though but no where near it's best and I think the other 2A3 was working harder to compensate, and I can confirm there was an imbalance after listening to the replacement pair.

Just one of those things which you have to accept as part of valve amplifier ownership.

Just to add, the material that's turned to milky white is called the Getter I believe.
02-06-2018, 15:32
chris@panteg

As a further update, I'm now using a matched pair of Psvane 2a3's along side the sovtek's, I wasn't sure about these but I've got to say they sound excellent so far and virtually identical to the sovtek's that I can tell anyway?

One thing I have noticed is putting a pair of RCA 6sn7's in, one per side is noticeably better sounding than the standard driver valves.
Very nice indeed, thanks Rob for including those in the sale of the amp.