I am trying to upcycle an old bit of tech I had lying about. The main part I am looking to recycle is the power supply however I do not have specs of the power supply itself. I have measured an output of about 5.5V with a multimeter but what more can be done to calculate/determine, the maximum load of this component.
Below you will see a photograph of the said PSU, the device actually has dual PSU (presumably for redundancy as the two were wired in parallel).
I have googled any distinguishing marks on the PCB with no avail: this was probably a proprietary board built for this machine.
With regards to components there are your standard capacitors, transformers, fuses and such as well as two components which I have been successful in finding datasheets for: PC123 and 30GWJ2CZ.
I am hoping someone can suggest which components I should look at to determine what the maximum load is or a practical method to test.
In terms of what I would like to achieve I would like to use this to power two raspberry Pis that would fit nicely in the chassis of this device. I am fairly certain there is enough power but I would like to determine more about this PSU before hooking it up and possibly look into ways of protecting the Pis from over voltage/current.
Best Answer
Most modern power supplies are not damaged by loading them more than intended. They will usually go into current limiting, shut down for a while, or at worst, blow a fuse. Some high volume OEM supplies designed for a specific use might blow up, but encountering one of them is unlikely. If you do, oh well, you're not worse off than before since you never actually had a power supply you could reliably use anyway.
Therefore, start at a relatively low load and keep increasing it (meaning drawing higher current or connecting lower resistance). While you do this watch the output on a scope. At some point it will start to sag or the supply will otherwise obviously object, like shutting down for a short while. Since the supply will be designed to the worst case, you will see this limiting behavior at a bit higher load that whatever the rating really is. I'd probably back off 20-25% or so and consider that the maximum rating. For example, if things start acting flaky at 10 A, then consider 7.5 or 8 A the maximum for your purposes.
If the supply has multiple output voltages then it gets more tricky. However, from the looks of it, your supplies have a single output. I'm guessing that each pair of wires (red and black) at the output are actually tied together.
From the general look and size of these supplies and the size of the output wires, I'm guessing around 100 W each.