leach amp power supply

[larryg]

a basic question? testing the power supply, 80vct@6a with rail
voltages of 56 to59 volts dc per specification. im checking the voltage from the
bridge rectifier dc +and -. the filter caps are not connected. i measure +and- 40 volts dc. the secondary ac is 42 vac. if the filter
caps were hooked up, would this bring the voltage to 56to59 vdc?
can someone explain this?

[paulb]

The filter caps charge up to the peak ac voltage, which is about 1.4 x the RMS ac voltage.
So yes. Even a fairly small cap will make a big difference in your reading.

[larryg]

thanks paulb! im a little confused. if the reading i get from the bridge rec is 40v, is this not dc volts?

[paulb]

No, it's not DC yet until it's smoothed out by a capacitor. If you had an oscilloscope you could see it. Your meter is kind of showing you an average value.
Some of these articles may help, although they don't address your exact question:
http://sound.westhost.com/articles.htm

[larryg]

thanks paulb very much! the site you show and your info helps me
to understand the answer to my question!

[Zero Cool]

The output of the rectifier is DC BUT has a large amout of ripple riding on top!

If you looked at the DC with a scope, you would see that the DC output is not perfectly flat, there will be large peaks still. your meter is reading the average of those peaks. the filter caps smooth out those peaks and flatted out the DC....



Zero

[larryg]

thanks Zero Cool!!