[AMRadio] Re: 810's

ne1s ne1s at neandertech.com
Fri Aug 24 17:51:35 EDT 2007

Todd, KA1KAQ writes:
> Rick, it's been a while for me, but the main issue I recall was
> expansion/contraction, with the envelope heating or cooling at a rate
> that the glue couldn't match, resulting in cracked tube or broken
> seal. It's been a long time though, so I really don't recall the
> particulars. 
> JB Weld is used on engines and other high temp applications as
> mentioned, so it would probably be fine. I run 810s as modulators and
> they do get hot, but I doubt it would be an issue. 

Guys, although JB Weld is good stuff, I'd shy away from it for this 
application. It's rigid stuff when cured, and if its thermal expansion 
coefficient differs "enough" from glass, something is going to give, and it 
will probably be the glass. 

I'd use high-temperature silicone (like the black stuff they sell for 
gaskets at the automotive stores), because it stays somewhat "squishy," and 
so will circumvent the above problem. That's what I'm going to try on an 
812A I have with a loose plate cap. 

JB Weld MAY work out OK, but... 


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