Superglue Warning
 

Andy Emmerson posted the following warning on the Vintage Wireless email list:

The January 2003 issue of the excellent American magazine 'Antique Radio Classified' contains two letters warning about the dangers of using cyanoacrylate glue, with trade names such as Super Glue, for repairing valves. I think the message deserves repeating here.

Restorers often need a fast-curing glue for cementing loose glass into valve bases but danger lurks here. The problem is the difference in the coefficient of expansion of glass and of the cyanoacrylate will cause the glue to act like a hot wire glass cutter - cleanly cutting the glass off at the base when the valve heats up to full operating temperature.

The bottom line is never use this glue on any valve or tube that runs too hot (when up to full temperature) to hold your hand on the tube. This means no power output valves and no rectifiers. However, this glue is considered safe, with some reservations, for battery valves and most small signal valves, if they don't get too hot.

Cyanoacrylate glue also makes a conductive path. When applied with the tube held in a vertical position, the glue can leak down into the pin area - not a good thing. It is suggested you use the gel-type version of this glue, which does not flow as easily. Or else apply the normal fluid glue with the valve in a horizontal position. For diaply and non-functioning exhibits there's no problem at all.


Credits go to Don Harrill in the USA and Gordon Wilson in Canada for these words to the wise.

Stever Ostler posted a message confirming that he had seen this effect with a PX4 in an RGD radiogram.

Re: Superglue Warning
 

Paul,

Do you think that there is any similar danger with making use of contact-type adhesives like 'Evo-Stick' for instance (apart from passing out from the fumes you understand)? How about the likes of 'UHU' or 'Aroldite'?

I have a lose base on an old CRT and was wondering how to tackle it.

Any comments appreciated.

Best regards,

Andy

Re: Superglue Warning
 

Hi
I have used Araldite several times for re-securing top caps and bakelite bases onto octal valves . It works very well.
Cheers
Tim

Re: Superglue Warning
 

I secured a lose Bakelite base to a CRT about 25 years
ago using car filler (Plastic Padding) and whilst the set
hasn't had a lot of use the base is still secure and the tube still works.

Peter.

Re: Superglue Warning
 

Car filler is good stuff you know.
It sticks well to metal, bakelite and glass, you can drill and tap it, it is heat and moisture resistant.
It's even better than Araldite!! I must confess I never thought of using it for mending valves. That's what makes this forum so wonderful!
I have repaired bakelite knobs and support pillars etc. with it.
Every workshop should have some!