Electrical connections without soldering
Making electrical connections when soldering is not easily possible or may cause damage.
Repair to a broken valve cap, for example, when the protruding wire is too small and non solderable, an alternative is to use conducting cements. This could be silver loaded two component epoxy.
Abrade the remaining wire with 600 or finer mesh carbide or alumina paper, and clean the tip with alcohol or any other suitable solvent, remove the old cement in the cap with a needle or steel point, clean the metal cap. Mix the two part conductive epoxy, fill the cap and press it on the valve tip. Wipe off the excess epoxy and allow to cure overnight. In this way, even if no protruding wire, a permanent electrical connection to the cap is obtained.
Conductive air drying silver paint can be used in place of epoxy in the same way, but it will have much reduced mechanical strength.
Broken connection to metal coated glass valves can be repaired in the same way, without any risk of cracking the glass envelope of the valve by soldering.
Conductive epoxy and silver paints are available from Maplin, RS, Farnell and many other suppliers.
Refrigerated storage is recommended; keep these away from children.
Hope you find it useful.
this article is an interesting topic and indeed has already earned some good voting from fellow repairmen. I think it truly deserves to be expanded and turned into a full article. What about adding some detailed pictures of your repair process? A list of the products you use could be very helpful for other people as well. Among others, you mentioned RS; what about adding a list of their catalog numbers to let us know which products specifically you tested and found to work fine?
Cheers - Marco.