[sdiy] Weird Ripple Voltage

[René Schmitz]

Hi Mike,

mike ruberto schrieb:
> More strange power supply problems. This time I have a high pitched
> whining in the audio. I traced it back to the devices power supply
> where it seems to be originating before the regulator. On the scope I
> see a ripple voltage with the usual saw shape but it is shot through
> with  lines. Increasing the volts division I can make out a tiny
> sawtooth wave riding on the ripple at several times the ripple
> frequency.
> 
> I disconnected the regulator to verify the origin and sure enough it
> coming form the rectifier/filter stage. That stage is a bridge
> rectifier with a ring of snubber caps and then the main filter cap and
> another 0.1uF cap. Am I looking at a problem with the bridge rectifier
> or is one of the snubbers bad?

That could be a resonance from the caps and the inductance of the 
transformer. I'd try to see if changing the snubbers capacitance makes a 
difference in frequency of that ripple.

Cheers,
  René