So much for all that palaver, reassembled but there were even less operative keys. Which left just the conductive plastic that miust be causing problems. I prized out one of these conductive plugs from its plastic well under the glass. There is a ledge in these wells, and now removed, the conductive cylinders are not solid all the way down but open to a hollow cylinder at the ledge which is very weak and splits at that point, even before my getting to it. The glass has some metalisation , perhaps nickel spray, on the rear of the glass. Screwing up some aluminium foil in these wells to make contact with the frail and resistive , order 1K across 5mm, and then fixing compression springs to the base pins to touch the aluminium has solved the problem.
Also soldering a piece of 26mm square brass to the 10mm diameter drawing pin then stuck in a base pin, shows that the variable base pins probably vary according to the (unseen as glass is glued to the plastic) variable areas of metalisation under each legend. With larger contact area (higher C ?) then finger injected rf would trigger easily through 1.5mm of glass or even 4mm of perspex.
As a refinement can anyone think of phospher bronze springs or something non corrodable for this application. I used ordinary steel springs. I tried fine heater element , whatever metal that is, but although it looks springy it is not reliably so - it relaxes. Or even where to find phosphor bronze wire from a non specialist supplier, to make some springs.
In the archives its obvious that a lot have people have been defeated by these B&O touch sensors - but the solution is now in the public domain.
-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on
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