Fixing Loose Valvebases

[M0FYA Andy]

Has anybody succesfully used heat-shrink tubing to solve the problem where the cement has failed between the glass and the bakelite base? There have been various threads on here regarding re-gluing, with no real concensus of a good method. At least heat-shrink would be a removable repair.

Andy

[Mr Moose]

Hello,

I have a number of new old stock ex military valves with B4 and similar bases that have what appears to be thick heatshrink round the joint between base and glass. I presume it was put there by the military stores.

I think it is probably being used prophylactically rather than to repair bases that were already loose.

Yours, Richard

[Tim]

Araldite works very well.

[M0FYA Andy]

I have to say I think Araldite always looks messy if used for this! I also worry that Araldite is probably too strong and will stress the glass.

I have used 'Weldbond' which is a PVA glue which is easier to apply than Araldite (less sticky and water-soluble before it dries, I don't mind wiping it into place with a finger-end!), and dries completely clear. However, this has only been for valves I have put into my 'stores' - I don't know how well it will survive a hot valve in use.

I think I will try to buy some suitably-sized heat-shrink and test it out in this application.

Andy

I dribble some cellulose lacquer down the gap, easy to get from a squirt of aerosol into the cap.

[Tim]

I pop a dab onto the end of a cable tie and "grout" the gap between the envelope and base.

[llama]

If you're going to use the heat-shrink method it might be worth looking out for the type with adhesive on the inside.
Graham

[ms660]

Another idea....high temperature silcon, the red stuff..this silicon will stick well to the glass envelope, this stuff will certainly take the temperature that most valves churn out. I have used it upto 200 c +
Cheers.

[theoldtrout]

I've successfully used clear nail polish [lacquer] It wicks down nicely between the glass and base and doesn't set too hard. I've also used it to stop arcing between tracks on a PCB.

[Mr Moose]

Hello,
Here is a picture of a VR21 with what appears to be heatshrink.

http://r-type.org/exhib/aaa0004.htm

Yours, Richard

[M0FYA Andy]

Another suggestion I have been given is to use shellac sanding sealer, as the original cement is shellac-based.
Lots of diverse ideas, thanks everyone.
Andy

[crackle]

What about superglue, it runs into every crevice, I swear by it, I dont see why it should not work for this application. As it is so runny it would also bond any of the original cement if loose or crumbling

[cmjones01]

Originally Posted by crackle

What about superglue, it runs into every crevice, I swear by it, I dont see why it should not work for this application. As it is so runny it would also bond any of the original cement if loose or crumbling

I hear that superglue is a bad idea for sticking glass. While it's very strong, it shrinks slightly when it sets. This stresses the glass and it breaks. How do I know this? Older Land Rover sliding windows have a little glass block glued to them as a handle. They fall off, inevitably. People glue them back on with superglue, and the glass then breaks, leaving a neat crater where the bond used to be.

I wouldn't risk superglue on valves, even though the glass is thinner.

Chris

[mickjjo]

Superglue is not a good idea on valves due to the risk of cracking, (using it to stick mirrors on car windscreens can be equally disasterous! ) see also:-

https://www.vintage-radio.net/forum/...se+valve+bases

Regards, Mick.

[Ebrew567]

fwiw I use standard Araldite around the joint but then bind 1 layer PVC electrical tape over the araldite. This forces glue into the joint. Leave it somewhere warm (hot water cupboard) 24 Hrs and then wind off the electrical tape. A nice fillet of glue remains.