SMPS troubleshooting

[Loial]

Hi again
I need a little help from someone who knows SMPS...
I've got a small 24 VDC/3.3VDC converter, and i think the regulation is out of order... I'm attaching how the pulsewave and FB-voltage looked like on the PWM-circuit before it died on me.
( forgive my bad painting skills 🙂 )


And does anyone know any forum about SMPS only?

 

[tekman]

Did you already look in sci.electronics.design?
A couple of SMPS guru are there

hth,
Andreas

 

[Eva]

Could you describe your circuit in detail or post an schematic? There is by far not enough information in your post in order to help you, and your picture shows just RF undamped diode-transformer ringing that gets radiated everywhere.

 

[Loial]

looks like i solved this one...

the secondary winding was open, resulting in no current flow, just a ring on the feedback.