envelope has come loose from base... advice?

[zappazapper]

hi there... i got my .50 cal + about 9 months ago, haven't really checked it out too much 'till now... it worked fine, no obvious problems so i just assumed everything was ok... but i've been sorta curious as of late about tubes and such and decided to take a look at mine...

it's got 2 coke bottle 6L6 STR 420s in it... the guy i bought it from said he had never changed the tubes, as he rarely used the amp, and i know these amps were made around the late 80's... anyway they sound fine, and look fine when the amp is on (ie. no blue, no glowing plates, etc.)... but i did notice something when i decided to take them out and make a more detailed inspection, just out of curiosity...

the one tube came out no problem... the other tube though, as soon as i touched it, i noticed that it was sort of "jiggley"... basically the envelope of the tube is not fully attached to the base like the other tube... after i manged to CAREFULLY get the tube out, i took a look and there is like some sort of clear substance that looks like dried glue that is supposed to be holding the envelope to the base (at first i thought it might be glass but i pulled a bit off and it breaks too easy... i tried to see if it was hard enough to make me bleed if i squeezed it in between my finger and my thumb but it wasn't... i know, kind of a cheezy test but, whadayagonnado?)...

another thing i noticed is that when i rotate the tube in my hand, i hear a sound like something is rolling around in there... no matter how i orient the tube, i don't see anything in the envelope, but there is a definite sound that the other tube isn't making...

now, i've been reading up a little on these tubes, and from what i gather, if there was a failure in the envelope, the getter would turn white, and as far as i can tell, the getter is that silvery stuff at the bottom of the envelope (ie if the tube is held with the base at the bottom and the envelope on top)... i can see no evidence of any white anywhere in this tube...

again, despite the fact that the tube is a little jiggly, it seems to work fine... it looks the same as the other tube when the amp is on, and the amp sounds great... but all the same, i just wanted to see if anybody around here thinks that there is something wrong, something that could end up damaging the amp in any way... if there's any risk at all, i'll get new tubes... if not, i'll leave them because right now they work fine as far as i can tell, and they sound great...

thanks in advance for any advice,
chris

 

[94Tremoverb]

You can work a little epoxy into the gap to hold the bottle - it's maybe worth doing because sometimes the wires inside can break if it moves around enough. The rattling noise is most likely a piece of scrap glass inside the base section of the bottle - inside the base but also inside the glass, if that makes sense! - and isn't harmful, although the rattling can be annoying. To be honest though, given the age and (not very good) quality of those tubes, it's probably best just to change them and not bother about the epoxy... keep them as spares if they work though.

Blue glow is *not* a sign of a bad tube by the way - quite the opposite usually. Tube Myth #1.

 

[zappazapper]

You can work a little epoxy into the gap to hold the bottle - it's maybe worth doing because sometimes the wires inside can break if it moves around enough. The rattling noise is most likely a piece of scrap glass inside the base section of the bottle - inside the base but also inside the glass, if that makes sense! - and isn't harmful, although the rattling can be annoying.

thanks so much for the response

the only time the bottle ever moved is when i touched it, and it doesn't make any rattling noises when i play, so... i'll see about the epoxy thing, but as long as you say it's not going to hurt anything, i'm happy...

To be honest though, given the age and (not very good) quality of those tubes, it's probably best just to change them and not bother about the epoxy... keep them as spares if they work though.

that was something i was just looking around for on the boogie board here... not very many definitive opinions on this tube, but generally i can see that not too many people are that hot on mesa tubes to begin with... STR 415s (if i remember correctly) seem to be the only mesa tubes that get consistantly good remarks, and they don't make those anymore as far as i can tell...

i might get the STR 440s mesa makes, only because i can buy them from the local music store and return them if they're duds, and they seem to be the lesser of two evils... i at least want something that WORKS first, then i'll start looking for something "special"

i've read alot about the RCA blackplate 6L6 reissues that groove tubes makes, but something about that whole thing just doesn't add up for me... they talk about how it's the same tube as was used in fender amps in the 60's, but that particular machine that GT bought wasn't made until the early 80's, so it's not the same tube, know what i mean?

people seem pretty split on JJ's too... seems like you have to get pretty lucky with them to get a good sounding reliable tube...

Blue glow is *not* a sign of a bad tube by the way - quite the opposite usually. Tube Myth #1.

ya i know that's one of those things that people are divided on... on wikipedia it says something like it could indicate a gassy tube, but the picture they use is like a professionally done promo picture for groove tubes... why would groove tubes take promo pictures of gassy tubes?!? "buy our new totally gassy tubes!!!"

actually several years ago i had a Marshall EL34 100/100 and the tubes were always blue... sounded great... i basically mentioned it just so i wouldn't have to answer the question if somebody asked

anyway, again, thanks for the response... i know this has been asked a billion times by everybody around here, but any tube recommendations you have i will certainly consider... i play everything from blues to country to rock to metal to punk to funk to disco to reggae to blah blah blah... not necessarily looking for something that is perfect for any one of those, just something that works pretty good for all of those...

 

[212Mavguy]

I had a coke bottle style tube that came loose, I used some cyanoacrylate type (Super Glue) and everything was fine after that. Seconding 94Tremoverb's words about the glass fragment(s), his words on the blue glow thang, also that maybe time for you to do some tube shopping.

 

[yeti]

i used that metal caulking stuff..bought it at pep boys or somwhere...it's a higher temperature rated metal sealant...on my last 6L6 that was loose.

and i've seen people use regular old silicone caulking too.