Loose valve bases

[SPCh]

Back in ancient times we used to have a very effective glue-free fix.
If the plastic-with-pins base was simply loose (i.e tension on the pinch wires was just slack) we'd wind a piece of 16swg copper wire round the glass at base level. This would force the base downwards, take up the slack, and stiffen the whole thing up. The shape of the glass was invariably "sympathetic". One or at most two turns, with a drop of solder on the twist to hold it firm, usually solved the problem.

[Nickthedentist]

Doesn't that put a lot of stress on the wires (and the seals where the wires enter the glass) though?

N.

[PJL]

I rebased a PM24A which had a badly cracked base. Although loose, the base had to be cut off as the glass has a substantial rim. Using the wire as a wedge would possibly only pull the rim back against the shrunken adhesive.

I have also successfully used the acetone and nail varnish trick recommended in an old thread.

[Dillen_de]

What did the factories use for securing the bases ?
Can't we use the same ?

Martin

[XTC]

I believe they used a shellac based cement. It softens or disintegrates completely if you soak it with an organic solvent such as meths or acetone.

I don't know what the filler was, but it may have been wood flour.

You can get shellac sanding sealer at DIY places.

Pete.

[G8DLG]

Why not use ceramic tile cement,this has worked great for me!

[Tim]

Car exhaust filler?

[FrankB]

I have re-attached the loose plate or grid caps using furnace cement- (Used here to repair cracks in stoves & furnaces. Very high heat stuff).
No problems so far on horizontal ouotput tubes, or transmitting tubes like 807 & 6146's.
I resolder the wire with silver solder also.

[russell_w_b]

Originally Posted by mickjjo

Hi Neil, I think the general opinion here is that two part epoxy type adhesives are best for this job, I tend to use the quick setting variety and have had no problems. Superglue is definately not reccommended! see here :-

https://www.vintage-radio.net/forum/...read.php?t=400

Regards, Mick.

There's some high-temp epoxy called 'J-B Weld', available, I think, from CPC amongst other places. I've used it in the past for attaching heat-sensors to Iron transformer core laminations and it (allegedly) withstands 500 degrees farenheit. If you do use it, though, take special care and protect your eyes from coming into contact with it.

[brymac]

I've got the problem with one of the PX4s in my Beau Decca amp - but there's also a loose connection which responds to the valve being moved. How do I repair the wire to pin connections - simply resolder them?? Bryan

[KEITHW]

An old way I read about of securing a loose base back to a valve is to make a collar from a bicycle inner tube. If you cut out a piece across the section, about a 1 1/2", you end up with a wide rubber band that can be slipped over the base and up over the glass, so half of the rubber is over the base and half over the glass.

Fully reversible too. Never tried it but it should be OK as long as the valve doesn't get too hot.

Keith

[brymac]

Thanks - but what about the electrical connections?? Bryan

[Ed_Dinning]

Hi Bryan, it is sometimes possible to re-flow the solder at the end of the pin. However if the base is also loose it would be better to remove the solder from all pins, remove the base, extend the wires (suitably insulated) and then resolder to the clean wire.
This trick is in several of the FJ Camm books

Ed

[FrankB]

I have had good luck using both Super Glue and GE RTV silicone seal ( aquarium grade- as the outgasses from it don't harm electronic parts) to tighten up the bases.

As far as the grid/plate caps go, I found using furnace cement (Handles high temps very well) to glue the caps back on works well, and then silver soldering the wire back on to the cap if needed.

I personally know one "local" used tube dealer who uses Super Glue on all the ones he sells here in the States.

[Phil G4SPZ]

I must admit, I was worried by the report that 'superglue' was the worst adhesive to use on loose valve bases I superglued the base of an original GEC KT66 recently, before I found this thread, and I only started operating the valve yesterday. Fortunately, it seems to be fine, and it hasn't shattered... yet!

Phil

[FrankB]

I have used furnace cement with good luck to glue the top plate/grid caps back on the tubes.
I don't see why it would not work on the bases as well.


The 807's & 6146's I tried it on have held up real well running "slightly" over the recommended current for plate load design ratings. Watching the plates turn from red to white with the key down is entertaining (Boy, do I need a real life.)

[brymac]

Thanks - I fixed this (some time ago!) by carefully unsoldering the base, fixing the loose connection, resoldeirng it and then runnig Araldite around the base. Job done!! Bryan

[maitiustandun]

hello, ive used fernox ls-x , on an old mullard valve in my philips 525a , also the top connection which was also loose , seems to have done the job no sign of melting , this compound is really for sealing plastic water pipes , best regards maitiu.

[ppppenguin]

Originally Posted by maitiustandun

hello, ive used fernox ls-x , on an old mullard valve in my philips 525a , also the top connection which was also loose , seems to have done the job no sign of melting , this compound is really for sealing plastic water pipes , best regards maitiu.

Fernox LS-X is a silicone sealant with quite a strong vinegar (acetic acid) smell. It's designed as a plumbing leak sealant and jointing compound though I would have doubts about using it on plastic pipes. A light smear on a compression joint or fibre washer can work wonders. I don't know if the acetic acid could be harmful to a valve.

[valveaudio]

I have succesfully used Loctite Body Filler (from Halfords) for some years on KT66s and the like. It's easy to get and dries quickly.

Take care with the silicone sealants most of them give off gas that is corrosive to copper although you can get special types from Farnell.

Trevor