[incognitoedleon]

I just broke a small piece of the tip of the tube on my phono preamp (Bellari VP129 if it matters). This may be a very dumb question, but does the tip of have any structural importance? Could a cracked/damaged tube damage the amplifier? At the moment, it appears to function fine. I just would like to know if the tube should be replaced right away and if there's any risk in continuing to use it.

The type of tube it uses is a 7025/12AX7A seen here. That tinier glass part at the tip on the top is what I broke off.

 

[d-cee]

well, if that crack extends into the vacuum section of the tube then yes that would render it useless because there would be no more vacuum

continuing to use it after that could possibly damage the amp

i wouldn't use it anymore as the crack could extend further and break the vacuum, especially while heating up/cooling down the glass becomes fragile

 

[M0T0XGUY]

Yeah, even if you managed to fracture the tip without ridding the tube of its vacuum, the 20 or so dollars you'd spend for a replacement could be considered a worthy investment as you wouldn't run the risk of damaging your amp further. Peace of mind, in other words, really is priceless.

 

[Sovkiller]

If you broke only the tip and there is no more cracks associated, (I had some tubes like that for years with no problems) but make sure it was only the tip that broke, IMO there should be no more problems, but if there is a crack, well chances are that while heating/cooling the tube it will break...if it is a good tube I owuld take the chances, if itis current production tube, do not bother and replace it....the 12AX7 is very common tube and you cna find easily a replacement for it...

 

[ironbut]

Without that curled tip, God can never lift that tube to heaven so don't let it die! Seriously, I wouldn't take a chance with a tube that may have any kind of crack in it. Especially new production since the glass envelope is usually thinner and more prone to cracking.

 

[incognitoedleon]

Thanks for the info! There aren't any cracks, but since it's a cheapie new production tube, I'll get it replaced. I was just hoping to safely use this one til the replacement arrives. I suppose it's not worth the risk.

 

[rivieraranch]

You could also cut yourself, too.

 

[d-cee]

Quote:

Originally Posted by rivieraranch /img/forum/go_quote.gif You could also cut yourself, too.

valid point

 

[GotNoRice]

I bought a pair of 6s19p-v tubes about 10 months ago from a fellow head-fi member, one arrived with the nub broken off and the tube ended up being noisy also. Not sure if that is typical, but it’s the only tube I have which is noisy like that (sort of a hiss that never goes away).

 

[jamato8]

If you fall on the sharp broken tip, well it wouldn't be pretty.

I have used tubes for years and would use it but that is my many years of experience and I don't have your tube in hand. I would also stick it in a tube tester and just let it sit there, which would put current on the filament, heat the tube up and so on and so forth. If just the tip no big deal but if you aren't sure then as you have stated, just get a new tube.