How hot do power tube glass bottles get?

[nevetslab]

I have another Fender Deluxe Reverb on the bench, finished the repairs on it, but did find one of the two Sovtek 6V6GT Power Tubes is somewhat loose within the Phenolic base. I went to apply some of my JB Weld Extreme Heat epoxy to solidify that, only to find the jar was now a solid block of material. Bought it in July 2019, though only stored it in the shop at room temp, rather than in the refrigerator where I store my super glues. No storage instructions or shelf-life details found on their data sheet or Safety Data Sheet.

I do have active JB Weld 2-Part Epoxy, which appears to be usable up to around 450 deg F.

Any idea how hot these tubes get?

[Helmholtz]

Some tube manufacturers specify a bulb temperature limit, e.g. KT66 : 250°C.

[Enzo]

Well, if I know my Bradbury, 451F is the ignition temp for paper. SO if touching a sheet of paper to your tube doesn't light it on fire, then I expect 450 degree goop will survive.

[Mick Bailey]

I used JB weld on my Vigilant multi-fuel stove. It cracked badly two years along the edges of one side plate so I took it out, stripped it down, then ground out the cracks and welded it up. I used regular JB Weld 2-tube epoxy to surface some weld imperfections - using it like car body filler - then rubbed it down and painted it matt black. The JB weld has held up just fine (this will be the third winter) and towards the top of the stove the heat will easily char paper, so I would expect the extreme heat version would be even better, though I have no problems with the regular stuff.

[Dave H]

Many years ago I used regular epoxy between the base and glass off a couple of loose EH 6V6s. They are running at 13W and are holding up just fine.

[Jon Snell]

At the base of the glass the heat will never exceed 70°C. The heat is radiated from the centre of the glass bulb in the middle of the anodes it peaks at maybe 200°C if an 813 or maybe a KT88.
I use Araldite (epoxy, the same as JB Weld).

[nevetslab]

This morning, after scraping off the residual glue (from JB Weld 2-part Epoxy applied last night) from the glass with an X-Acto blade, did same on the tube base, then cleaned it up with Alcohol, it was now solid and stable. Plugged it in, powered up, and all is back to normal. Can't charge for that effort, as the question would then be if you charge me for this glue-job, why not just replace the tubes, as the cost would be the same. Steady customer, so just one of those many bonus services they get from a detail-oriented tech. They're bringing more gear over today, while picking up the four that are here. That's always music to my ears.

[Mick Bailey]

I use Araldite (epoxy, the same as JB Weld).

Araldite has a much lower maximum temperature than regular JB weld. The spec sheet I have for standard Araldite gives 65C as the upper limit. JB Weld is 500F (260C) with up to 600F for 10 minutes. Araldite begins to soften at higher temperatures where JB weld holds firm.

[Randall]

I would not charge for that effort, but I damn sure would tell them about it!

[nevetslab]

I would not charge for that effort, but I damn sure would tell them about it!

I did mention that in the invoice work details