Project 001 – Fixing an old (Boss) power supply

If you’re like me, you have a whole bunch of these kinds of power supplies all mangled up and lying broken in a box or tossed in a drawer somewhere. Instead of throwing them out and buying a new one, here’s a simple 15 minute process for returning your power supply to good as, or better, than new working condition.

First thing to do is to open up the case of the power supply. Some are much easier than others to open, depending on how old they are and how badly they’ve been abused, but with enough convincing you should be able to open them up without cracking the case or doing any other damage. I found that a combination of a razor blade and a flathead screwdriver did well to pry the two halves apart. The bolts holding the case together will first have to come out using a 5/32″ socket.

Next thing you will have to do is to desolder the wires where the cord connects to the PCB. Take some desoldering braid and remove the solder around the holes and the wire should pull right out.

Save this piece of wire that was just removed, because it can be reused to support and protect the new piece of wire that will be going into the case. Score the piece of wire just behind the plastic piece and then pull the rest of wire out with a pliers. Now take this plastic support and drill an 1/8″ hole through the center. A drill press will help get a straight hole, but a regular drill would work just fine with a vise. I used a punch to push the remaining pieces of plastic out from the hole so that the wire would fit through.

As long as the rest of the wire on the power supply is undamaged, this can be reattached to the PCB to return it to working condition. The weakest part of these power supplies is the point where the wire goes through the plastic wire support piece, and the problem almost always lies in this joint. By placing some heatshrink over the cable, the wire will be better supported than how it is originally put together, and likely to be more durable.

First, trim the cable down so that all the damaged wire is removed. Then, strip, and tin the wires with a little bit of solder. Before resoldering this cable to the PCB, remember to put on a piece of shrinkwrap about one and a half inches from the end your wire and then slide on the plastic support piece. Another way to project this joint is to tie a knot in the wires just behind the plastic piece so that it cannot be pulled out of the case.

Last thing to do is to put the case back together and make sure it works! Close the case and reinstall the screws with the 5/32″ socket.  Once it’s all together, plug it into an outlet and test the output with a voltmeter. The center of the plug is negative on this type of power supply.

Here’s what it looks like when it’s all put back together. The joint connecting the wire to the supply should be much more durable now with the heatshrink and wire-through design of the support. To think I almost went and bought a new one…