Riddled TV Repair Forum

John1397 · Joined: 16 Aug 2007 Posts: 44

When AC (125 volts) power enters a circuit board that has a full wave bridge then as it is changed to DC and you place a capacitor (1000 mfd ) from plus to negative how much current in terms of AC millamps would this draw assuming no load condition?

John

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Davy · Joined: 04 Mar 2012 Posts: 13

Depends on the diodes and the leakage current of the capacitor... I feel more important is if we take 125V AC rectify it in a bridge or full wave rectifier you would end up with...

125V ac x 1.4 which equals and would give you 175V peak off-load.

In a half wave rectifier, that is just a single rectifier this would be 125V x 0.707 which is 88.375V peak.

The voltage in both cases would drop when you start drawing an appreciable amount of current.

So do remember to take this voltage in consideration when choosing your capacitor, the capacitor must be able to stand the applied voltage, the surge is another factor with such a high value capacitor which the rectifiers will have to handle as well.

Dave