Securing a loose anode cap ?

[Yorkie]

Wasn't the original cement wood-flour and shellac? As you say epoxy is fine and I'm chiefly just curious as it's always interesting to know how things are/were made.

- Joe

Yes Joe - got it in one.

If ever you wish to remove a valve base or top cap (having unsoldered the connections such as at the valve pins or top cap of course), if you soak the base or cap in meths, which is a solvent for shellac, it will dissolve the cement and you can tweak the base or cap free. To make up a similar cement, you need a small amount of shellac (French polish or shellac sanding sealer - NOT cellulose) and some wood flour, which you can obtain by using say 80 grit sandpaper on a piece of scrap wood. Make a stiff mixture, and use some elastic bands to hold the top cap or valve base in place overnight until the cement sets.

Initially, when rehabilitating an EBL31 valve, I tried cellulose thinner as a solvent for the original cement, which didn't work. It was only when I researched it further that I learnt that originally, they used shellac and wood flour and that meths would dissolve the cement, as indeed it did, though no doubt as time progressed - in the post-war era - they used other types of cement, perhaps epoxy based, were used.

If using Araldite, various types have various upper temperature limits before they will dissolve, so if the valve is going to get quite hot, it's worth checking the spec. I'd concur with advice about not using superglue as it isn't flexible, and I've heard of cases where (allegedly), it has cause the glass to crack on heating up. Whether htis is just an 'urban legend' Ive no idea but on a rare and costly valve, it is't something I'd want to put to the test.

Hope that helps.

David