How to build a $20 47A power supply

[BrianG]

Little update on boosting the output for those interested. I ended up using a couple of resistors to make the voltage divider instead of a diode; a 210 ohm and 20 ohm. This gets me ~13.2v. I was able to get to 13.6v, but the supply sometimes wouldn't turn on or stay on. 13.5v worked fine, but I brought it down to 13.2v just for a little extra wiggle room.


First, the stock power daughter board. There is a blue and purple wire which I cut. One is a 5v line, the other is a -12v line.



Then, I cut away where the 5v and -12v lines were to make room to run the wires for the voltage booster resistors. I soldered pins 6 and 10 directly to ground to turn the PS on. Even when these aren't connected, the PS is on somewhat so I figured I'd just hardwire them and use the mains plug as a power switch. I then soldered wires to a ground point, +12v point, and to pin 5 (v adjust pin).



On the other side of the daughter board, I attached those three wires to the resistors and hotglued the resistor pack to the PCB. I did have to remove the bolt lug from the case so the resistors would fit.



Here is a simple schematic to show how to arrange the resistors. The power ratings of the resistors, especially the 210 ohm one, should be 2w or more.



As you can see, I soldered the binding posts directly to the blade plugs. The soldering job is good, it just looks crappy because as I soldered one side, it would drip down. Since the pins themselves weren't being used, I ground them all down.

Here is another pic showing what I know of the pins: