What does this "knob" do ? [twist] - Overclock.net

yuandrew · 10-24-06

While cleaning the fan in my PSU; (an inexpensive 400 watt unit made by SuperPower) I spotted a potientiometer similar to this one

hidden between some components. Being a little curious, I decided to give it a twist just to see what would happen. Nothing happened much on the 12 volt rail but I did notice a slight change on the 5 volt. Without anything connected, I adjusted it to 5.00 volts from the original 4.97. However, back in the computer, I took readings again with my multimeter and it reads 5.04 volts.

3.3 rail still ranges from 3.35-3.40. The 12 volt rail still seems to go anywhere from 11.89 to 11.98 all the time depending on load.

Anyone ever messed with hidden potientiometers before ? I know common sense would suggest you don't just go and start turning whatever pot you see on a circuit board but I'm sure some have been curious or knew they were doing.

accskyman · 10-24-06

I've seen a few posts about having POT's inside PSU's, it could just be an easy way for the manufacturer to adjust the rails to the correct power. Could be useful to overvolt things, but theres obviously a high risk to that.

Dryadsoul · 10-24-06

It's a trim pot for one of the rails. Put a load on the PSU and measure the volts in both extreme positions to find out which rail. There are several mods on the net that show you how to add trim pots to all your rails, if you add holes to the side of the PSU you can adjust them on the fly.