Fact or Fiction?

[MCK]

I was reading about biasing a BFSR on the net and noted one posters comment below :

You want to make sure your hands are clean, as you do not want to deposit grease or debris on the glass part of the tube because it can cause it to fail. Set the tube aside on a clean cloth.

Is it a fact or fiction that the grease from your hand deposited on the tube's glass envelope can cause it to fail? I know not to touch halogen light bulbs but I never cared too much about the amp tubes... Nothing failed on me so far but maybe thats because I don't keep my hands greasy to begin with... Thoughts?

[dartanion]

Fiction.

[LeftyStrat]

In theory yes. In practice, I've never seen it happen. It might be true for high voltage transmitter tubes that get really hot.

The basic premise is that it would create uneven heating/cooling on the glass that could cause it to crack.

On the other hand, if you've just plunked down big bucks for a set of NOS EL34's, wiping them down after touching them certainly is a valid precaution.

[MCK]

Heavy build up of gunk could also affect the heat exchange. I do wipe my tubes and keep them clean. Was just curious thats all. Thanks for your comments.

[Structo]

Yeah, probably not a good idea to eat a cheeseburger while installing tubes.

Just keep your hands clean and of course it won't hurt a thing to take precautions such as this.

I think what got this started was the Halogen headlight bulbs for cars that say you shouldn't touch them with bare fingers when installing them.
But those get much hotter than vacuum tubes so the precaution is warranted.

[dartanion]

Never seen it happen, but it's possible. I have had amps come through my bench that had burned on greasy finger prints all over the power tubes. Didn't effect their performance. Will they burn out faster? I don't know if anyone has tested that, but I'd interested to know.

[ckpop]

Funny someone mentioned this........I had a customer bring a amp by last week and I pulled a tube with my bare hands and was asked if I should be touching the tube ? All the years I have been working on amps this only came up recently ? Of course I always wipe power tubes down is I see a a finger print but it's just my OCD !!!!!!! Never heard of this and never had any issues. You have to ask do where do these idea's come from ??????

[MCK]

For the record, I was not that customer!

[LeeMo]

I just happen to have a zip-lock bag full of tubes on my desk that are pulls from a 1966 Hammond organ. They are covered in oil from the tonewheel lube that dripped on them from above for 50 plus years. They were working when I pulled them. There was a "made in Britain " 12ax7-ecc83 with the turn on "FLASH" in their midst. It was labeled Hammond as were all of the others.
I would say the myth is "Busted".


LeeMo

[MCK]

Busted! Thanks much for that.

[LeftyStrat]

I just happen to have a zip-lock bag full of tubes on my desk that are pulls from a 1966 Hammond organ. They are covered in oil from the tonewheel lube that dripped on them from above for 50 plus years. They were working when I pulled them. There was a "made in Britain " 12ax7-ecc83 with the turn on "FLASH" in their midst. It was labeled Hammond as were all of the others.
I would say the myth is "Busted".


LeeMo

I would never expect it from a pre-amp tube, they really don't get that hot. I was more thinking about my days as a kid hanging out at the radio station that my step father was program director. Those high voltage transmitter tubes might be affected.

Kind of funny, I had a pyrex baking dish explode on me the other day, going from hot to cold. Apparently they are not made the same any more. I remember a commercial from the old days, with one half in a block of ice and the other half in flames.

Damn, my kids aren't even out of high school and I've already become "Grumpy Old Man":

http://www.dailymotion.com/video/xkp9co ... ld-man_fun

[selloutrr]

Where have your hands been? Personally fiction

[Reeltarded]

I am still making that face my mother told me would stick if I kept making it. I only make it around her. She's very confused.

[Reeltarded]

Funny someone mentioned this........I had a customer bring a amp by last week and I pulled a tube with my bare hands and was asked if I should be touching the tube ? All the years I have been working on amps this only came up recently ? Of course I always wipe power tubes down is I see a a finger print but it's just my OCD !!!!!!! Never heard of this and never had any issues. You have to ask do where do these idea's come from ??????

Me too. Never before, and three times in a month. Pop unculture. Let's be superstitious. It's fun, but very harmful to reason.

Reality wins in the end.

[LeftyStrat]

Me too. Never before, and three times in a month. Pop unculture. Let's be superstitious. It's fun, but very harmful to reason.

Reality wins in the end.

Didn't your mother ever tell you that touching your tube would grow hair on your palms?