(https://www.vcfed.org/forum/forum/genres/pcs-and-clones/71625-xerox-6060-restoration) I have laid out a simple 3" by 3" PCB with the following features: - takes 20- or 24-pin ATX power supply connector as input - routes the GND, +5V, +12V, and -12V rails to appropriate connectors for attaching the original Xerox 6060 / Olivetti M24 / AT&T 6300 internal cables - boosts the 12V rail to 15V using a XL6009 IC (this can be disabled through a jumper if not needed) - has a 3-pin fan connector to power a 12VDC fan - has a jumper cluster to select four possible speeds for the fan - has a jumper for the ATX "power on" switch (if jumpered closed, the ATX power supply will turn on as soon as the mains switch is operated) - has three status LEDs (5V stand-by, main 5V, and boosted 15V) - has a 3.3V post for future expansion / in case you need this voltage for something else (low amperage only) In my mind it is meant to be attached to the side of the original power supply enclosure, with the ATX cable attaching from the back and the Xerox cables attaching at the front. This way it will also receive some airflow from the fan. ============================ The holes on the PCB for the thick Xerox/6300/M24 power cables are for M4 screws, which fit the metal connectors well enough (well, with a bit of persuasion for one of them... or you could use M3.5 screws). The PCB connectors for the CRT and +/-12V are not the same as in the original but they fit well - if anyone knows what exact model number the original connectors are (they are made by AMP) pls do let me know... The 15V voltage regulators works like a charm - it heats up far less that the pre-built version I originally got from eBay, probably because the PCB and the heat dissipation pads I put in are larger, and the support components I chose are over-specified. Also I originally intended to put in an “angled” ATX connector but I created the PCB footprint for a straight-up one I already had, assuming the angled one I had ordered (but not yet received) would have the same one, but alas... no. So straight-up it is. ============================ The ATX PSU innards are already inside the old M24 PSU chassis. The adapter board would most likely fit inside as well (maybe bolted upside down to the ceiling of the old enclosure) but it would make cable routing quite messy. What I plan to do eventually is to bolt the adapter board to the outside of the original PSU chassis with some metal standoffs, on its side between the PSU and the ISA slots. There is enough space there for the adapter board (maybe a couple of inches?), good access for the cables that need to reach it, good airflow (not that it needs it), plus the (very bright!) status LEDs would be easily visible, instantly telling me if the PC is on or not (just joking, but seriously, with the new fan even in a very quiet room you can’t hear the difference between the ON state and the OFF state) ============================ The problem with modern ATX power supplies is the depth - and there just isn’t that much space depth-wise inside M24s. The original PSU is just 112mm deep, which isn’t very much. A quick search on amazon shows this one which at 4” deep might just be thin enough to fit: https://www.amazon.com/300W-Power-Supply-Replacement-Dimension/dp/B0107GP8FS/ however the fan/mains connector/screw positions are likely to be in the wrong place with respect to the original case (which will be true of virtually every modern ATX PSU). However, at 25$ it might be worth a shot. If you have the time I quite like the way I did it, ie gutting the old PSU and replacing the insides - it’s not particularly difficult, but it’s a bit fiddly and time consuming (it took me a whole day) even if you have all the hardware bits at hand. If you are interested in going this way I can write down a list of bits you’d need (mainly some metal standoffs, screws, spade connectors, some wire, a drill, and a soldering iron). The advantage of doing it this way is that you maintain the look and feel of the original, and reusing the original PSU case means no problems with fixing screws, the switch/mains are still in the same place, etc. If you do decide to gut&replace, I would strongly recommend a Startech PSU - I have bought several and they are very reliable (and I know the PCB is the correct size), although twice the price (around 50$) of no-name ATX PSUs. So in answer to your question - I switch it on and off using the original switch at the back of the Xerox If you go the other route and put another PSU in, the M24-ATX board has a jumper called “PS ON” that, when closed, tells the ATX PSU to switch itself on. In my case I just leave it jumpered in the closed (on) position since I control the mains power via the original switch, but if you use a power supply without an external switch you can connect a simple open/closed switch to this jumper and use that to control the power supply (one of those old “turbo button” PC switches with a twisted cable that ended in a little 2-pin connector would work perfectly here). Also - a PicoPSU would probably work too, actually. I did consider it - and it would definitely solve the space problem - but the thing is that it just moves the problem further down the line. You then need to find an external 12V power supply of sufficient rating (not impossible, but quality in that field varies wildly). Also the PicoPSUs I have seen have a borderline sufficient current rating on the 5V rail - you’d be using it a max spec all the time - not something I am comfortable with (I like wide comfort margins in all my specs...).