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Author Topic: High Temperature Tube Glue for 811s ?  (Read 2732 times)
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W4DNR
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« on: December 19, 2019, 07:47:56 PM »
Four 811s laying sideways in a 30L-1 .

While replacing the diode board, I noticed one of the glass envelopes
was not connected to it's bakelite base.

What is the best fix ? JB Weld or Permatex  hi-temp silicone ?   

I don't want to start a fire in the ham shack... LOL !

Don W4DNR
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KA0HCP
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« Reply #1 on: December 19, 2019, 09:27:51 PM »
Furnace cement, $5, Ace Hardware. 
https://www.acehardware.com/departments/heating-and-cooling/chimney-and-flue/chimney-brushes-and-accessories/46623

Works on loose plate caps too.
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New callsign KA0HCP, ex-KB4QAA.  Relocated to Kansas in April 2019.
W7TFO
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IN A TRIODE NO ONE CAN HEAR YOUR SCREEN


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« Reply #2 on: December 20, 2019, 11:27:54 AM »
I've had good luck with 'flowable silicone' from Dow.  Creeps down in easily, stays 'rubbery' without coming loose under heat.

73DG
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KA0HCP
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« Reply #3 on: December 20, 2019, 12:36:49 PM »
To honest, just about anything will work for securing the base.  I've even found tubes with Elmers glue on them.  The base is cool enough that epoxy or high temp (orange) RTV work fine.

The furnace cement is perfect for securing plate caps, though.
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WBear2GCR
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Brrrr- it's cold in the shack! Fire up the BIG RIG


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« Reply #4 on: December 21, 2019, 11:07:08 PM »
Flowable silicone - sold for sealing auto window glass.

The furnace cement - depending on the type  (not all the same) - works when one has complete access to
a large surface, tough on tube bases unless one desolders the pins and pulls the base off.

Epoxy weakens with heat. (some are better than others)

YMMV.
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WU2D
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« Reply #5 on: December 22, 2019, 10:08:12 AM »
Ah Plastic Wood?

* 991eb1206da6f9aaca94e10edcbd8150.jpg (28.82 KB, 286x320 - viewed 234 times.)
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KA0HCP
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« Reply #6 on: December 23, 2019, 12:23:12 PM »
Quote from: WU2D on December 22, 2019, 10:08:12 AM
Ah Plastic Wood?
Works fine for Audiophile tubes with 'woody tone".  Smiley
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WBear2GCR
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« Reply #7 on: December 23, 2019, 08:25:19 PM »
Quote from: WU2D on December 22, 2019, 10:08:12 AM
Ah Plastic Wood?

Nope - wrong stuff.

It shrinks on drying and has zero bond to glass.

The actual cement used on tubes bonds to glass, does not shrink.
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