Converting ATX into lab supply trouble

Question

I have been trying to convert an ATX power supply into a lab power supply and ran into some problems.

The first one was that the banana plugs I bought had metal nuts and screws, so I used electrical tape and drilled bigger holes to prevent them from being shorted to the case. This seemed to work I had also made a switch to turn it on and off by shorting the green wire to ground.

I plugged it in, flipped the switch, and the fan came on but there was no power out of any of the banana plugs (the wires are all soldered to the screws).

Then I tested the plugs and the +5 V wire was shorted to ground and then I tested and somehow every other wire that was not in a banana plug got shorted to ground (except the +5 V banana plugs; they were shorted).

So I have no idea what to do or how to even find more information to help myself. Could someone point me in the right direction or tell me what tests I can do to find the problem?

Answer 1

Some ATX power supplies are not stable without load and may not start or may turn off.

Double check your connections so that they are not shorted. Or any other loose wires dangling inside the supply. It would not be a good thing if some wire touches mains referenced things inside, such as heat sinks which may be live with mains. Usually it is not a good idea to go do connections inside power supplies if you already get the wires out of it.

Then check if it needs some load to turn and stay on.

If it does not work it may already be damaged.

And ATX supplies are finicky and poor as lab power supplies. They may need special tricks to turn on and stay on, and even then, they may not be used for powering any arbitrary loads you can think of, because it is easy to violate the ATX power supply specifications.

If you switch on a too high capacitive or resistive load, it might take too large inrush current surge and overcurrent protection might turn it off.

If you disconnect a too high resistive or inductive load, the power supply may not react quicly enough and output voltage may rise too high, and overvoltage protection might turn it off.

ATX power supplies are best powering computers which is their intended use. They start and stop consuming current within the defined ATX specs and load all outputs in some fashion so they are not difficult loads for an ATX supply.