Loose Valve Cap - UK Vintage Radio Repair and Restoration Discussion Forum

sparkymike · 1st Sep 2014, 9:14 am

Can I use a dab super glue or hide glue to secure a top cap on a 6V6 valve that is slightly loose ?
Mike.

M0FYA Andy · 1st Sep 2014, 9:47 am

A 6V6 with a top cap? Errrrr.........

Andy

sparkymike · 1st Sep 2014, 9:55 am

6C6 (typo !!)

Station X · 1st Sep 2014, 9:57 am

I've always used Araldite Precision for this. I understand that super glue can cause the glass to crack when it heats up.

hansomcommon · 1st Sep 2014, 9:58 am

Probably not as I have never seen a 6V6 with one, I do use superglue to lock top caps on valves which have them, with no problems so far, but others council against as apparently there can be thermal stress problems on hot running valves.

cmjones01 · 1st Sep 2014, 9:59 am

I'd avoid super glue, if I were you. As I understand the issue, when it sets, it shrinks slightly, and bonds so strongly to glass that the shrinkage cracks the glass. I don't know how risky this is with the thin glass of a valve, but I wouldn't chance it. Other, softer adhesives (and hide glue may be one of them, but I don't know) will be safer.

Chris

threeseven · 1st Sep 2014, 11:17 am

What was originally used?

Station X · 1st Sep 2014, 11:25 am

I don't know, but I'm sure if you search the forums with suitable search terms you'll find out.

https://www.vintage-radio.net/forum/...ad.php?t=57584

richrussell · 1st Sep 2014, 12:20 pm

There is another formulation of cyanoacrylate (ie superglue) designed for use on glass. It's used for attaching rear view mirrors to windscreens for example. You can get it in motor factors (eg Halfords), but I suspect most DIY places would have it too. I've used it to repair a broken level gauge tube on an oil tank, which was still intact after several summers and winters where it must have cycled through a reasonable temperature range. That was about 0.5mm glass, so probably not too different to a valve top cap.

trobbins · 1st Sep 2014, 12:26 pm

I've found that RTV or industrial grade silicone rubber (with temp rating to circa 200C) is great for loose top caps and Bakelite bases.

1st Sep 2014, 9:14 am	#1
sparkymike Octode Join Date: Dec 2006 Location: Colchester, Essex, UK. Posts: 1,076	Loose Valve Cap Can I use a dab super glue or hide glue to secure a top cap on a 6V6 valve that is slightly loose ? Mike.

1st Sep 2014, 9:47 am	#2
M0FYA Andy Nonode Join Date: May 2007 Location: Preston, Lancashire, UK. Posts: 2,511	Re: Loose Valve Cap A 6V6 with a top cap? Errrrr......... Andy

1st Sep 2014, 9:55 am	#3
sparkymike Octode Join Date: Dec 2006 Location: Colchester, Essex, UK. Posts: 1,076	Re: Loose Valve Cap 6C6 (typo !!)

1st Sep 2014, 9:57 am	#4
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,289	Re: Loose Valve Cap I've always used Araldite Precision for this. I understand that super glue can cause the glass to crack when it heats up. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

1st Sep 2014, 9:58 am	#5
hansomcommon Pentode Join Date: Jan 2014 Location: Alton, Hampshire, UK. Posts: 170	Re: Loose Valve Cap Probably not as I have never seen a 6V6 with one, I do use superglue to lock top caps on valves which have them, with no problems so far, but others council against as apparently there can be thermal stress problems on hot running valves.

1st Sep 2014, 9:59 am	#6
cmjones01 Nonode Join Date: Oct 2008 Location: Warsaw, Poland and Cambridge, UK Posts: 2,679	Re: Loose Valve Cap I'd avoid super glue, if I were you. As I understand the issue, when it sets, it shrinks slightly, and bonds so strongly to glass that the shrinkage cracks the glass. I don't know how risky this is with the thin glass of a valve, but I wouldn't chance it. Other, softer adhesives (and hide glue may be one of them, but I don't know) will be safer. Chris __________________ What's going on in the workshop? http://martin-jones.com/

1st Sep 2014, 11:17 am	#7
threeseven Octode Join Date: May 2010 Location: Worcestershire, UK. Posts: 1,880	Re: Loose Valve Cap What was originally used? __________________ BVWS member

1st Sep 2014, 11:25 am	#8
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,289	Re: Loose Valve Cap I don't know, but I'm sure if you search the forums with suitable search terms you'll find out. https://www.vintage-radio.net/forum/...ad.php?t=57584 __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

1st Sep 2014, 12:20 pm	#9
richrussell Heptode Join Date: Jul 2008 Location: Selby, North Yorkshire, UK. Posts: 979	Re: Loose Valve Cap There is another formulation of cyanoacrylate (ie superglue) designed for use on glass. It's used for attaching rear view mirrors to windscreens for example. You can get it in motor factors (eg Halfords), but I suspect most DIY places would have it too. I've used it to repair a broken level gauge tube on an oil tank, which was still intact after several summers and winters where it must have cycled through a reasonable temperature range. That was about 0.5mm glass, so probably not too different to a valve top cap.

1st Sep 2014, 12:26 pm	#10
trobbins Heptode Join Date: Oct 2009 Location: Melbourne Australia Posts: 901	Re: Loose Valve Cap I've found that RTV or industrial grade silicone rubber (with temp rating to circa 200C) is great for loose top caps and Bakelite bases.