Expensive control amp/ preamp Scratchy motorised/sevo volume control. Anyone been here before, any pifalls opening up etc ?
-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on
Not made to be taken apart. Long rivets and star circlip. Unusually , constant but fairly low level of crackle over 80 percent of one track. Presumably loss of plating on conductor track so varying different metal Seebeck voltage or chemical corrosion perhaps .
-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on
With this sort of problem cannot see resistance amisss by checking with a DVM. Worn track but only worn down, not through. 3 sets of wipers per pot and 3 circular paths, conductor, 100 K resistor and low resistance inner ring of about 20 ohms around. Probably problem due to corrossion over most of the wiper fingers and this central contact ring. The pitfall is a not noticed/seen, presumably cartouche shape widget, that locates that shape hole in the pot paxolin to the smaller same shape of axis shaft. I must have removed both together thinking they were one part and lost the widget before placing in tray or sticking to something else and losing. Had to fashion one from a couple of transistor insulated washers and epoxy.
-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on
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