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ATX Variable power supply circuit problems? Answered

I finished putting together the variable power curcuit board I had asked about earlier. I am getting 0-18volts with no load applied just my meter.
When I try to connect a small dc motor or anything to it , my voltage goes to 0. I used a 5k linear taper potentiometer and didn't notice untill after assembling that it is only rated for .5 watts. Could this be the problem? I also used a salvaged ceramic cap, and a salvaged 1uf cap, but dont know how to test them with a regular fluke multimeter. Could somebody please help! I'm a newbee, so I appologize for my electronics ignorance, but we all got to start somewhere.



Best Answer 7 years ago

There is a brown or pink "sense" wire that needs to be connected to one of the 3 v. wires or you won't get the power supply to work. IIRC.

Also "some" power supplies won't work unless there is some load on the 5 v. lines.

The power rating of the pot should not be a problem. It us just a control line and doesn't pass much current. IIRC.

Thanks for everyones help, I'll keep chugging along at it.

Try hooking it to a small light bulb or low current load. A motor, even a small motor is almost a direct short.

Is there a web site anywhere that shows how the components and wires of a circuit should be aranged in plain english instead of schematic form.

Without the regulator circuit hooked up the power supply works fine. I have a +12,+5, ground,and a -12 volt binding post, and they all work right. It's when I connect my variable voltage circuit up that Im having problems. With no load on it, it seems to work fine checking it with my multi meter, but when I hook up even the smallest little motor to it I lose everyting. It doesn't trip the safety or anything like a short, I just have no voltage. This is the second one I've built and both do the same thing. Help Please! I'm new to the forum but i'll try to get some pics on here.