Conductive paint: where from?

[WRCC]

This company Agar supplies a variety of silver loaded paints intended to create conductive paths on specimens examined in electron microscopes. Not cheap, but they have a very high silver content.

[singlepentode69]

Maplins used to sell this in spray and in the paint on form like a bottle of nail varnish if that is of any help . I used to use this to repair the keyboard cables on the early Sinclair cables and calculators .
Robin

[Radio Fixer]

Here is an extract from an article I wrote. This stuff is really good but only buy it from somewhere reputable (Farnell for me) as it has a shelf life of about a year from memory. It really does seem not to spray too well after this ...clogging I guess. It really does produce great low R screening and Yes! you really do need it this good for Philips SI sets.

"This is Electrolube Nickel Screening Compound, with a resistance of less than 1 Ohm / Square, from DC to blue light, sold by the larger electronic component suppliers. It’s expensive at about £20 a can but of course amortised over a few valves maybe acceptable.

I cleaned the valves, masked off and prepared a spray booth from a large cardboard box. This is essential, as is a proper respirator and goggles, as it's a dusty business. However, once sprayed and allowed to dry the results were impressive. From the metalising pin, to the top of each valve, a typical result was 1.5 Ohms with no wire wool pad needed for connection, just a probe.

From weighing the can before and after, and knowing how much the makers said was in there, it was apparent that it would only be good for four valves of this size, or possibly five, with experience and if used more sparingly than I did.

The same friend, who had used the spray before, told me that a primer is needed if it's used on the bare glass of stripped valves: without this it falls off. Not having any Weld Through Primer I phoned Electrolube Technical Sales but didn’t get a positive recommendation. They readily agreed with my suggestion that Zinser spray shellac, which seems to adhere well to everything, might work.

I had a good SG20 DC valve, which are very rare, that had almost zero metal coating left so it was ideal to try. After cleaning and scouring with emery cloth, I soldered a band of de-solder braid around it as a pickup to the old copper drain wire. Then, after cleaning with thinners and masking off, I tried a couple of coats of Zinser before the nickel spray the following day (after removing the masking over the pick-up band of course). Over a few weeks, a few cracks appeared in the finish but it hasn’t flaked off. Possibly a shrinkage problem with the primer and next time I’ll try putting the valve in the valve tester for a few hours before the nickel spray. On the valves that had secure metalising, and were nickel sprayed directly, then no cracks have appeared. "

Gary