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Combining PSU rails together

R

Red Squirrel

[H]F Junkie
Joined
Nov 29, 2009
Messages
9,217
I have an old PSU I tend to use for testing, powering 12 volt stuff, and overall just messing around with.

Would it work if I cut all the wires, and just combined all the rails together, so I have a single 5 volt and single 12 volt rail? I don't really care about the others, I'd probably cap them off, and ensure the power button portion is solderd together. Would this actually give me more power in a single rail?
 
You can connect multiple 12v leads together that are from different rails if you really need that much power to power a single 12v device.
 
cool so that will work? I was not sure if it would just maybe damage it. Obviously all - to - and + to +.

I basically want to make it cleaner instead of having so many cables and rather then waste rails, may as well combine. This will be a workbench PSU for anything from testing fans, to powering up random electrical experiments. :D Electrolysys and such too.
 
Google power supply mod or some such, there is an article on conversion to either a lab supply or all 12 volt.
 
It should be safe to connect multiple +12V rails together. There will be a bit of current flowing backwards due to small voltage differences between wires, but it won't be very much.
 
I ended up doing it and just used one wire per. I pulled up the board and it looks like all the wires are actually soldered together. Would it be typical for a cheapy PSU to actually be single rail? I thought only the more expensive ones were like that. I also never realized there was a -12v connection. It tickles when I touch that and the +12v at the same time. :D

I used romex wires sticking out of the grill as terminals and put a label for each. I have +3.3v +5v +12v 0v -5v and -12v. Plenty of combination for various needs. I think I will buy some crocodile clips and modify a few molex female connectors as well. I was going to just make them built in, but I like the clean look of no wires sticking out at all. I can clip on the connectors as I need, for testing fans and what not. Also makes it easy to test fans at various voltages such as 5v instead of 12v.

I also have this coil I made with spare cat6 wiring. Woah, I can magnetize a screw driver in like 5 seconds. :D
 
It is extremely common for cheap PSUs to be single-rail units. In fact, it is more expensive to manufacture a multi-rail PSU than a single-rail PSU, because single-rail PSUs do not require any OCP circuitry.
 
Oh that's good to know, I figured it was the opposite. The PSU I used was marked defective, I forget why but think it had tendancy of browning out or something, so at least I know to just buy a cheap one if this one goes. This one is good enough for my uses, and so far it's stood up to some pretty nasty loads like a 2.2 ohm coil I made to magnetize screw drivers. It makes a funny noise but it works lol.
 
In general, cheap PSUs 1) passthru power line irregularities to powered components, 2) are sensive to temperature[ may lose performance, quality of power, or both], 3) do not meet ATX standards, 4) are labeled with lies.
It is not unusual for the only "real" circuit protection to be the soldered in fuse.
 
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