hacked PC powersupplies

[dinges]

A few years ago, someone on this forum taught me a little trick to convert nearly-useless old PC PSUs into fancy lab powersupplies. Admittedly, it took a few years of him teasing me and proverbially kicking my butt to get into action and actually modify a PSU. But ever since, things haven't been the same anymore.

We're now a few years on and about half a dozen PSUs have been converted, and the tricks of the trade have been shared with a few friends who now have also modified a few PSUs of their own. And we've no one for it to blame but a fellow on a slightly-deserted island on the other side of the world....

Maybe he'd like seeing some of the stuff people have done, thanks to his gentle (and sometimes not so gentle....) prodding:

This is the PSU that gets used the most - doesn't look the part, but definitely a workhorse: 2.5-24V adjustable, at 0.25-10A current, also adjustable.



The more luxury and better looking variant, but used much less often:





A lab powersupply, consisting of one standard conversion, 2.5-28V @ 10A, and a 2nd PC PSU that has been modified with a full-bridge rectifier to yield 15-55V @ 5A. (there's a 3rd,  non-modified industrial PSU in it as well to supply standard +/- 5, 12 and 24V)





Above, another PSU; originally a 48V/30A phonecompany batterycharger, that has been hacked; only the power bits have been left in place, the actual controller has been replaced with a TL494 hack-job to give a 5-58V/30A powersupply.



And the above project is in the works: similar to the 30A PSU above, but this one for 100A. Originally a 3-phase 48V batterycharger (defect), that is being modified to 220V single phase and 5-60V output, at up to 100A (not 100A @ 60V.... at least, not without blowing the house circuit breaker....)

And then there are the various other projects, where an Oztules-modded PSU is powering everything.... as in this CNC controller....



Anyway, the reason for this post.... am now building a hotwire styrofoam cutter.... and guess what it will be powered by.... So figured some credit was due.

So thank you, Oztules. Your help and patience haven't gone by unnoticed in my life. And thought you might be interested in seeing these projects, which have been largely, or at very least partly, inspired by it.

Just wanted to say that.

[oztules]

Kinda gone teary eyed almost.... very nice work you do Dinges.

You know, once you have done a conversion, you can never walk past another computer power  supply without looking at it differently than pre mod days.

Did you find any better ways to do it than the down and dirty original system? I particularly like your boxed versions... darn fancy.

I have built/converted a lot of them over here for battery charging at constant rates for standby generating plants, but they are so versatile and darn handy voltage  and or current sources, I don't know what I did without them.

Glad to have helped Dinges ( in reality I thought I was just annoying him, didn't realise I was actually helping .... curses    )

Thanks for the show and tell....... Oztules

[dinges]

Kinda gone teary eyed almost....

Hehehe... did I embarrass you?

You know, once you have done a conversion, you can never walk past another computer power  supply without looking at it differently than pre mod days.

Yep, it was what you said back then and what you were entirely correct about.

Did you find any better ways to do it than the down and dirty original system?

For the PC PSUs it's the quick & dirty method, with a shunt resistor in the transformer's return line (flying lead). The 30A PSU didn't have such a return line (full-wave rectification) so used a shunt in the negative output line and an opamp (schematic: https://picasaweb.google.com/motorconversion/Mitra30AVoeding#5580650491770185202) to buffer the voltage and provide some protection against too much negative voltage to the TL494.

But it's basically always a slight variation on the same theme. And surprized it always seems to work so good, without having to mess with feedback loops, time-constants or determining poles and loop-stability (which is beyond my ability).

Maybe if you applied a very drastic stepped load that you see some over- or undershoot, or an under/overdamped oscillation as it settles to the new equilibrium.... but that's not really much of an issue for me in practice.

They just do the job - period. No fuss. No damage when I make the occasional (usual?) goof. So pretty foolproof, once you've made the mods.

And yes, can't help but snicker every time I leaf through the electronics stores' catalogs and see all those fancy and expensive power supplies, and seeing a 1000+$ apparatus that has worse ratings than the thingy I threw together myself. That gives me some satisfaction

Haven't yet tackled rewinding a transformer yet, but that'll come too, in time. Still would like to have a variable 50-300V dc supply with a bit of ooomph.....