(08-12-2011, 08:04 PM)ThePillenwerfer Wrote: Putting capacitors across it gets a nice flat line . . .
(a) Would they be capacitors (a) across the d.c. O/P, or (b) across the input primary winding?
If (a) then there is a serious failure of the rectification and filtering of the d.c. voltage.
If (b) then there is severe harmonic distortion, probably caused by a partially-failed mains transformer or one with an inadequate core size.
The whistle is due to the high harmonic component of that waveform. Cases (a) and (b) will cause this.
Al.
