Something to do while watching some less engaging TV. Unwound another large toroidal mains transformer. Suspecting doubled up winding of the primary and then for UK use joining opposite ends and so relying on 2 thicknesses of lacquer to resist high voltage. Of course somewhere near the middle at some point it fails catastrophically. Yes, burnt spot weld buried in the middle of the primary. Anyone know what this duff winding technique is called ? (reduces the number of shuttle passes by 2 must be the reason). Is there a way of testing an unknown , but good , transformer for this winding pattern ? How come this wiring procedure is not outlawed ? More generally, someone in production told me that a "goodness" test for a mains transformer is an open secondaries, no load, monitoring of the primary current is useful, any truth/rationale in that. ?
-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on