power supply hum problem

[al]

i have a 0-600vdc 0-200mA solid state power supply, hums when i raise voltage with no load to 250vdc & above and hums noticeably with a load. I replaced can electrolytics with new computer grade, i had to replace with larger values, i.e. 300uF were replaced with 470uF same WVDC. Any ideas?

[viveguy]

The transformer may not have enough current available to keep the caps filled up.If you have a scope, check the output ripple.Be careful that you don't exceed the input voltage rating of the scope though.<p>AL

[russlk]

look for rivited or corroded connections. Resistance in the ground return will cause hum.