[sdiy] Weird Ripple Voltage

[mike ruberto]

Got it! I case I missed something I started working my way back into
the power supply from the rectifier and noticed a very large spike on
the base of a pass transistor. Changed the transistor and problem
solved.

Very strange, because the output voltages were correct with the faulty
transistor. This turned out to be an interesting challenge. Learned a
little something about snubber circuits because of it too.

Mike

On Sat, Apr 5, 2008 at 9:06 PM, mike ruberto <somnium7 at gmail.com> wrote:
> no luck changing the snubbers. I've replaced them all with no affect.
>  Looks like I need another strategy.
>
>
>
>
>
>  On Sat, Apr 5, 2008 at 4:21 PM, mike ruberto <somnium7 at gmail.com> wrote:
>  > And according to Cornell Dublier Metallized caps are not recommended
>  >  for this application due to limited pulse current handling.
>  >
>  >  Good thing I checked. I was about to use the metallized ones in my
>  >  parts box. I'll have to cannibalize the ceramics off an old television
>  >  motherboard I have and test them now.
>  >
>  >  Mike
>  >
>  >
>  >
>  >  On Sat, Apr 5, 2008 at 3:53 PM, mike ruberto <somnium7 at gmail.com> wrote:
>  >  > I'm thinking I have a bad snubber cap. However, before I take any
>  >  >  drastic action I am trying to educate myself in the topics of ringing
>  >  >  and snubber design. So far this has been most helpful...
>  >  >  http://peufeu.free.fr/audio/articles/Snubber%20Networks%20in%20Power%20Supplies.pdf
>  >  >
>  >  >  The math is quite above me though for the most part. Still at least I
>  >  >  have a better idea of what's going on.
>  >  >
>  >  >  Considering the negative rail is not having this fault at all I will
>  >  >  assume the proper values are being used for this supply and start
>  >  >  replacing the snubber caps one by one in the positive rail rectifier.
>  >  >
>  >  >  This whole experience makes me wish I had better test equipment ;-)
>  >  >
>  >  >  Mike
>  >  >
>  >  >
>  >  >
>  >  >  On Sat, Apr 5, 2008 at 3:40 PM,  <KHeck73 at aol.com> wrote:
>  >  >  >
>  >  >  >
>  >  >  >
>  >  >  > I've had some weird experiences using the same AC power circuit that powers
>  >  >  > dimmer controls for lighting. If your lighting is usually on, try switching
>  >  >  > it off and see what happens. For my circumstance, I think it was the square
>  >  >  > wave off the triac making harmonics...  -Karl.
>  >  >  >
>  >  >  >
>  >  >  > In a message dated 4/4/2008 9:41:25 P.M. Eastern Daylight Time,
>  >  >  > somnium7 at gmail.com writes:
>  >  >  > 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?
>  >  >  >
>  >  >  > Mike
>  >  >  >
>  >  >  >
>  >  >  >
>  >  >  >
>  >  >  >
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>