Quote:
Originally Posted by Herald1360
Could the twisted pair lines be transposed giving wrong polarity dc? .
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Quote:
Originally Posted by russell_w_b
Pretty sure there'll be a bridge-rectifier across the line feeding the ancillary circuits, given that line polarity can change arbitrarily or determined by switching sequences, without ill-effect.
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I did open the 'phone up, early in my investigations. I did see four diodes on the pcb that were located near to where the incoming line meets that pcb.
Al.