Most makers find themselves in need of a benchtop power supply at some point or another. Basic models can be had relatively cheaply, but as your current demands go higher, so does the price. [Danilo Larizza] has figured out an alternative solution—repurposing old server hardware to do the job instead.
The build is based around an HP Common Slot (CS) server power supply. They can be readily had for well under $50 if you know where to look. Even better, they can deliver over 50 amps at 12 volts, which happens to be a very useful voltage indeed. All you need to do is some minor mods.
A jumper on a couple of pins will get the power supply running, and with the addition of some terminals for your hook-up leads, you’re ready to go. As a hot-swappable single unit, the power supply is already outfitted with a ventilation fan to keep everything cool. If so desired, you can even make some further mods to bump output voltage a little ways past 13 or 14 volts if you’d like to use them for certain battery charging tasks.
Sure, you’re not getting a variable power supply, but if you need 12 volts and lots of it, this is a great way to go. We’ve featured similar builds before, too, turning ATX PC power supplies into useful benchtop tools.
Server PSU’s tend to be quite loud. Changing Fans to get them silent is mostly not an option because they check rpm and unless it is an exact match the power supply will turn off in a fail mode.
Laptop Bricks on the other hand mostly get you 6 – 10 Amps of 19 Volts (moddable to 12 or 13.8 if you want) Without making any noise at all. They can be had for a similar price.
Those platinum ones with 94% efficiency are said to be mostly silent when you draw about 60% rated wattage, so if you need 400W get 750W one (HSTS-PL/PD29), see discussion here https://www.reddit.com/r/EtherMining/comments/pdug7c/hp_power_supplies_running_silent_on_66_load/
I cannot confirm myself yet but I just researched this topic too and few days ago ordered PL28 (460W) for BC-250 which draws about 220W and hope it will be silent too. some videos on youtube confirm this too like the guy here https://youtu.be/NndDN4fpq64?t=475
I got 9 of them powering GPU in my basement , I don’t hear them outside my lab
I have used one before as a basic power supply, it was not loud at all, given I wasn’t drawing much current from it.
I would think many people on HaD can make or acquire a little pulse generator to feed the fan connector with whatever frequency that tickles it.
And the rest can probably ask some AI to draw them a schematic and a give them a parts list right?
I almost vomited in my mouth, considering those could just buy a standalone pc fan controller module from their favorite purveyors of cheap far-eastern tchotchke.
Especially considering they’re guaranteed not to have the parts in stock themselves to throw something like that together anyway.
I bought a bunch of really old HP servers at a government auction about 10 years ago. The storage arrays were populated with 60 gig SCSI HDDs to give you an idea how old.
Anyway most of the fans were like 40 or 60 volt .5 amp or something crazy. I think I have a few of them still floating around somewhere because I don’t throw things out even when I really should.
There are more interesting ways of using server psu like patching firmware:
https://github.com/darwinbeing/HPServerPSUHack
and nice monitoring with data provided directly by PSU firmware:
https://github.com/darwinbeing/zpsu
I find these psu almost silent in many cases.
I fished a variety of PSU’s including some of these pout of some old servers a while ago – the hobby RC community have hacked various models to give them fast charging for their battery packs so the info is out there.
I’ve yet to find a fan speed control pin though – I’m sure some of them just run full speed all the time but I reckon at least a couple of models must be able to throttle down for quiet operation.
I use one of mine to run big 12v loads in the workshop – old 12v battery drills can be had for free, if you’re got a 50A 12v PSU handy you’ve got a good quality drill that will run all day.
Hmm I can buy these for real cheap, much less than what even a 700W a ATX PSU would cost me. Since my PC is basically a 170W GPU + 65W CPU, I currently have a 550W PSU in it but I do want to buy another couple of GPUs
Is it possible to get adapters for these server PSUs that will let me connect an ATX cables? Or will I have to cut and solder the ATX cables directly (do these even have 3.3V and 5V rails? or will I need converters to make them from 12V).
I don’t even mind designing a board, the price is really nice for 1200W PSUs
There are adapters that have the edge connector and break out all the cables to heavy gauge wire. I have a bunch of the HP’s that produce 200A with 220V input (100A I think with the 120V). I got them for some experiments 15 years ago. And some Bitcoin mining I should have stuck with! Much as I thought I wold find them very useful, I have not used them since. ……. Checking eBay the adapters have dropped way down in price. In fact $10 for one with 12 of the 6 pin connectors! Example https://www.ebay.com/itm/234438388098 and interesting, the PSU’s are now $15 to $20. I wonder how well they handle 12V stepper motor loads.
They do great running a 3d printer
Ive used one for that before.
Ofc 24v is more standard these days, but if you’re not chasing speed or have an older 12v unit they work great
Damn haha are you me?
I was doing the same in 2013. Bought some HP 2kw 12v supplies for $50, and 4 graphics cards initially to mine with running off a Z77 Pro3 (Litecoin and Feathercoin, but the idea was to swap them to bitcoin).
The plan at the time was to use it for heating in the winter, then sell off the cards come summer. Sadly I didn’t realize how unstable I was at the time, and I was always getting sick, so any project only had a lifetime of a month before I moved on from it, so I never managed to really make it work. Too bad because it would have worked out well. Sold off the parts, but I still have one of those supplies
I used a pair of Bitmain miners for supplemental heat for 3 years and earned a fraction of a BTC through a pool of cool guys in Australia. I should have kept even that little bit. Oh well, I should have kept my Apple stock from 1985, etc. etc.
You can get boards for them that were for crypto mining so they have connectors on them for GPUs. Make sure that your grounds are the same and you will probably be fine, just like when using multiple ATX power supplies.
Have a look over here:
https://www.knightli.com/en/2026/04/16/csps-common-slot-server-power-supply-pinout/
If you search for “CSPS” or “HP PSU Adapter” or “PSU Power Supply Board” chez the usual Asian interweb vendors, you ‘ll find exactly what you are looking for !
Another source for cheap high-current 12V supplies is those used by bitcoin miners. A Bitmain APW3++ 1600W PSU can be found for not too much, sometimes with an obsolete miner included.
You do actually get a module that allows controlling current and voltage. I just found this on AliExpress:
Ternary Lithium Battery Charger Control Module Is Suitable for Workstation Retirement Power Module
https://a.aliexpress.com/_EHGBURk
See video how to use control module: https://youtu.be/rRM_0THcy2U?si=-4Pth_sFNky1xm9u
These things are real work horses too… A decade or so ago I ganked an 800W unit that takes 110-240VAC and outputs clean regulated 12VDC from an e-waste bin at work (our lab had just moved to 48VDC distribution) and I still use it whenever I need a beefy 12V rail for something (from running a winch to lighting off fireworks to feeding a hungry flyback driver to make wild plasma arcs).