O Ring for Tube damper?

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mattymel
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O Ring for Tube damper?

Postby mattymel » Sun 02/13/11 5:33 pm

Went to an auto parts store looking for an O ring hOokup. Found some black ones the guy said were heat resistant up to 1200 degrees. The question is if he knows for sure? Most I see for sale as actual tube dampers are red. And these look like plain rubber. I may try it and keep an eye on them but I wanted to see if anybody had any similar experience/melted rubber bands on tubes? Thanks!
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Postby mattymel » Sun 02/13/11 6:21 pm

looking around online, from what i see, similar looking rings are heat resistant up to about 400 degrees. im guessing El84s are quite a bit cooler than that?
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Postby tubeswell » Mon 02/14/11 3:32 am

Virtually any O-ring you buy from a hardware store should be okay (as long as it fits snugly).
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mattymel
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Postby mattymel » Mon 02/14/11 4:20 am

experience so far...
no melting.
still a little rattle, but now it doesnt seem to be microphonic. instead just a rattle coming from the amp itself, but not through the speakers.
ie...good enuff 4 me.
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Postby rsi » Mon 02/14/11 11:16 am

The rings I have been using are black. I got them from an auto parts store. Two rings have been on the EF86 in my 18W head for at least a year and I have not had any problems with them.
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CurtissRobin
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Re: O Ring for Tube damper?

Postby CurtissRobin » Mon 02/14/11 1:42 pm

mattymel wrote:Found some black ones the guy said were heat resistant up to 1200 degrees.

Consider that we often touch or wiggle or even pull the operating preamp tubes with our fingers when we troubleshoot and don't raise blisters. That says that you don't need 1200° O-rings. Nearly all the heat emitted by an amp comes from the PT, power tubes and a few of the resistors.
Most I see for sale as actual tube dampers are red. And these look like plain rubber.

Red is a more appealing color and sells better than black to people who are looking for mechanical damping rather than fluid sealing. O-rings come in dozens of materials and colors according to their uses. Neoprene, Teflon and Buna-N are widely-known trade names for a few materials and most of them are black. Here's a link to information from one of the benchmark companies making o-rings
http://www.parker.com/portal/site/PARKE ... ky=O-RINGS
I may try it and keep an eye on them but I wanted to see if anybody had any similar experience/melted rubber bands on tubes? Thanks!
I'm sure no preamp tube generates enough heat to affect any of the o-ring materials you'd buy from an auto parts or local industrial supply store. Find a couple that fit and get a couple thicknesses since the thin one may be enough or the thicker (heavier) one may be needed. The particular elastomer used is unimportant but the mass (weight) is what does the damping.

KennyO
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Postby mattymel » Mon 02/14/11 9:30 pm

any suggestions as to HOW tight you want the rings to be? i imagine as tight as possible, and now i guess as big as possible too...
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Postby CurtissRobin » Tue 02/15/11 10:54 am

Bigger is NOT necessarily better and too tight defeats the damping action you're installing it for. The elastomer is as important as the size so go by trial and error and, being a musician, play it and use your ears.

Any thickness between .080" and .140" should do fine. It should be tight enough that it won't move up or down when you move it or play the amp and that's not very tight. Position the o-rings at the point where the internal structure is in contact with the glass envelope. The lower one probably won't have any discernible effect and if the upper one doesn't seem to do much, add another of the same size there instead of changing to a larger one.

Remember that some tubes are noticeably microphonic and some are not. If the tube in there is not, drop the o-rings into your repair kit for a future tube that rings like a cracked bell. Of the microphonic ones, some are helped by installing o-rings and some are not. Once more, play it and use your ears.

KennyO
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