# Tube with a "broken leg"



## Stratin2traynor (Sep 27, 2006)

I have a matched pair of EHX EL84s that I removed from one of my amps. I noticed after I had removed it, one of the legs was broken off. There doesn't seem to be any damage to the tube itself, just the leg is snapped off. 

I threw those tubes into a Blues Jr that I'm working on and saw that the "broken leg" doesn't seem to be part of the circuit, it just soldered to the PCB, presumably to help keep the tube in place.

The amp seems to sound ok but to be honest, I am not 100% sure because it was dead when I got it and this is the first time that I fired it up successfully.

I figured that since that particular leg does not appear to be part of the circuit and the glass enclosure is not damaged, it should be ok. 

So are there any tube connaisseurs that can comment on this?


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## -James (Dec 11, 2014)

Hi,

Sounds like you broke off pins 1, 6, or 8. None of these are connected internally. 

You could break off pin 9 and operate it as a triode, but I'd use a switch instead.:smile-new:

-James


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## nonreverb (Sep 19, 2006)

Just check around the stump to make sure they're are no small stress cracks. If their are, it may slowly loose it's vacuum which will present itself rather quickly after a certain threshold is reached.


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## Stratin2traynor (Sep 27, 2006)

How will that present itself? Will the tube just fizz out or burn out?


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## dtsaudio (Apr 15, 2009)

Loss of vacuum in a tube is evident from the almost instantaneous creation of a white powder film inside the tube. The tube is then scrap.


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## nonreverb (Sep 19, 2006)

Interestingly, I observed a tube with a small hairline crack that very slowly lost it's vacuum. However, it was out of circuit. I suspect if it was plugged in it would fail far more rapidly....


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## Stratin2traynor (Sep 27, 2006)

Interesting. My tube is still crystal clear so I guess it's ok. I do, however, have a 6V6 somewhere that has that problem. I think it might be toast. I haven't plugged it into anything for a while.


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## Church-Audio (Sep 27, 2014)

replace the tubes.... really if you broke a leg off its a sign from god that it needs to be replaced replace them both. My favorite tube for that amp is a Tungsol or JJ EL84. www.thetubestore.com while your at it take it to a tech and get them to bias this amp properly. Your tubes will last longer and the amp will sound better.


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## Stratin2traynor (Sep 27, 2006)

Sound advice - no pun intended. Alright maybe just a little. I was hoping to be able to use those tubes but you're probably right. Time to dump them. As for biasing, I have the Billm mods coming in the mail, one of which has to do with biasing the amp.


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