As a person who knows only enough to do some basic electronic repairs and diagnostics, not an engineer of any kind, I just wanted to give my 2 cents on this... I think having updated guts for retro PSUs is a really cool idea. That said, these would need to be certified in some way or be successful and widespread before I'd feel safe running something like this long term.

I assume that only people who know what they're doing could complete a project like this, but when you're dealing with mains voltage and hundreds of watts distributed to what could be hundreds or even thousands of dollars worth of vintage components... not to mention having it possibly hooked up long-term in my home... yeah. From the beginning I would prioritize safety and maybe even look into some kind of certification, if at all possible.

Sure, and therefore I'm against designing mains powered AC/DC PSU, and thats why I took DC-DC approach, where everything stays low voltage (you need an external brick, but I don't think its a big issue).

You could put DC DC board inside hollow AT PSU case and just put a barrel jack or USB-C connector instead of mains plug.

Ozzuneoj wrote on 2026-10-28, 13:41:

I assume that only people who know what they're doing could complete a project like this, but when you're dealing with mains voltage and hundreds of watts distributed to what could be hundreds or even thousands of dollars worth of vintage components... not to mention having it possibly hooked up long-term in my home... yeah. From the beginning I would prioritize safety and maybe even look into some kind of certification, if at all possible.

Which is why I'd take ready to get AC/DC power supplies and then just do the low voltage stuff. It's a tough nut to crack for such a project. Who do you want to appeal? And how are people supposed to use it - especially one that are into retro computing, but have no interest or knowledge in soldering etc. That brings me back to the original question I asked earlier.. "How diy do you wanna go?".
Nobody would seriously want to go through the hassle of getting certifications for a niche thing like that. That's where already made parts from LiteON, MeanWell, Delta etc. could come into play. Or any other free marked external power brick.
There you'd have the most dangerous part out of the way.

adalbert wrote on 2026-10-28, 14:17:

Sure, and therefore I'm against designing mains powered AC/DC PSU, and thats why I took DC-DC approach, where everything stays low voltage (you need an external brick, but I don't think its a big issue).

You could put DC DC board inside hollow AT PSU case and just put a barrel jack or USB-C connector instead of mains plug.

Again, boils down to the question what you want in the end? original experience with the mains going into the system? Then you'll need to have the AC/DC part in there as well. Which form ever.
I'd take off the shelf hardware for that and do the 12V to rest myself.. others have solved the AC/DC game already, no need for me to hassle around with topology, parts choice, PFC, transformer design and production etc..

Overall then you're back at the point of having DC already, so why not use one of the already existing DC/DC solutions out there that work happily with 19(or 20) volts and adapt from there.

tehsiggi wrote on 2026-10-28, 14:24:

Again, boils down to the question what you want in the end? original experience with the mains going into the system? Then you'll need to have the AC/DC part in there as well. Which form ever.
I'd take off the shelf hardware for that and do the 12V to rest myself.. others have solved the AC/DC game already, no need for me to hassle around with topology, parts choice, PFC, transformer design and production etc..

Nope, I don't want mains going into the system, basically what I want and what is sufficient for me, is a better version of Pico PSU, with additional protection circuits (that protect the mainboard from overvoltage/converter failure) and beefier converters for 5V and -12V/-5V rails. So there will not be any AC connector in the system at all. AC/DC conversion will be done by a certified power brick/charger. So there will be no electrocution risk for the user, and everything is considered extra-low-voltage, safe to touch. It will look like on the image below, you can 3D print mechanical adapters that allow to fit different PCB and connectors in original case. So it will be different than the original, but should still look clean.

tehsiggi wrote on 2026-10-28, 14:24:

Overall then you're back at the point of having DC already, so why not use one of the already existing DC/DC solutions out there that work happily with 19(or 20) volts and adapt from there.

Existing DC-DC solution like Pico PSU usually have pretty basic protection circuits and are not tailored well for load on rails used on old PCs. Also, I don't think I have seen an open hardware design of such PSU yet.
Most common failure mode of DC-DC converter is a MOSFET switch going short, and then you get full 20V going into 5V rail. Sure, it doesn't happen often, but it can happen, and if you are paranoid about safety, you need to use extra precautions (you can't RMA a vintage mainboard and get a new one in case of failure).

adalbert wrote on 2026-10-28, 14:35:

tehsiggi wrote on 2026-10-28, 14:24:

Again, boils down to the question what you want in the end? original experience with the mains going into the system? Then you'll need to have the AC/DC part in there as well. Which form ever.
I'd take off the shelf hardware for that and do the 12V to rest myself.. others have solved the AC/DC game already, no need for me to hassle around with topology, parts choice, PFC, transformer design and production etc..

Nope, I don't want mains going into the system, basically what I want and what is sufficient for me, is a better version of Pico PSU, with additional protection circuits (that protect the mainboard from overvoltage/converter failure) and beefier converters for 5V and -12V/-5V rails. So there will not be any AC connector in the system at all. AC/DC conversion will be done by a certified power brick/charger. So there will be no electrocution risk for the user, and everything is considered extra-low-voltage, safe to touch. It will look like on the image below, you can 3D print mechanical adapters that allow to fit different PCB and connectors in original case. So it will be different than the original, but should still look clean.

The attachment connectors.png is no longer available

That question was more general to the original poster of this topic. It appears that his goal is to have the mains going into the system like before. Thus he mentioned the AC/DC part explicitly. And that's why I've raised the question about it more than once, because I'm not sure what the hard requirements of this project here are.

That your project does not want AC in the system is clear from the get go and was not in question.

adalbert wrote on 2026-10-28, 14:35:

Existing DC-DC solution like Pico PSU usually have pretty basic protection circuits and are not tailored well for load on rails used on old PCs. Also, I don't think I have seen an open hardware design of such PSU yet.

That is true. As much as I like the idea of an open hardware project like yours, the question remains on what users without the capabilities to manufacture it themselves will do, right? That's again the question of "how much diy do you want to get".
I wouldn't mind going all in from my end, but that's easy said because I have the knowledge, tools and skills on that. But others might just wanna get their beloved old machine going and can't go that route.

adalbert wrote on 2026-10-28, 14:35:

Most common failure mode of DC-DC converter is a MOSFET switch going short, and then you get full 20V going into 5V rail. Sure, it doesn't happen often, but it can happen, and if you are paranoid about safety, you need to use extra precautions (you can't RMA a vintage mainboard and get a new one in case of failure).

I can understand that fear, though I myself hadn't had no PicoPSU (like) models fail on me like that, the oldschool designer in me would think about putting a crowbar circuit in between the PSU and the rest of the hardware.

Again, this is not a question of "does it make sense". It really depends on what you wanna achieve. Which is why I repeat myself with some questions trying to figure out what the OP wants with his project idea in the end.

tehsiggi wrote on 2026-10-28, 14:38:

That question was more general to the original poster of this topic. It appears that his goal is to have the mains going into the system like before. Thus he mentioned the AC/DC part explicitly. And that's why I've raised the question about it more than once, because I'm not sure what the hard requirements of this project here are.

Okay sure, I just wanted to add my two cents and the AC/DC part concerns me too, so I may address the original poster as well with my concerns and just throw that issue into the discussion.

Speaking about the DIY and technical skills concerns, i think the design could be optimized in such a way that someone just could order a ready-to-use board from a PCBA manufacturer, assembled on demand, with a group buy or something like that.

adalbert wrote on 2026-10-28, 14:45:

tehsiggi wrote on 2026-10-28, 14:38:

That question was more general to the original poster of this topic. It appears that his goal is to have the mains going into the system like before. Thus he mentioned the AC/DC part explicitly. And that's why I've raised the question about it more than once, because I'm not sure what the hard requirements of this project here are.

Okay sure, I just wanted to add my two cents and the AC/DC part concerns me too, so I may address the original poster as well with my concerns and just throw that issue into the discussion.

Speaking about the DIY and technical skills concerns, i think the design could be optimized in such a way that someone just could order a ready-to-use board from a PCBA manufacturer, assembled on demand, with a group buy or something like that.

Yeah, jlcpcb and others have full assembly services, so that could be an option. Which adds more questions to the dreamy idea of the OP 😀

Also worth mentioning here: AT(X)Anything: a modular DC-DC PSU for old PCs (open hardware)

Something like this would be ideal for a high expense/high safety angle.

MEAN WELL NMS-240-5. Input AC lines. Output 180W 5V 36A. Has every certification. $66USD
https://au.mouser.com/en/ProductDetail/MEAN-W … 5zXDDhlvA%3D%3D

There's a 12V module as well at a similar price, but two of those would mean the price starts at $133USD before PCB costs ($30-50), but there is practically nothing else remaining cost-wise because the modules do everything.

It was part of a modular PSU.

For an OEM design, another issue is the cables. Is the user now tasked with cutting each cable at the old PSU internals, keeping track and inserting into a new connector or soldering... or are the cables pre-soldered and come with the new PCB, adding to cost.

I recently came across to this:

https://github.com/neo-internalforce/ATX5Vbooster

From this video

https://youtu.be/BrJlWmi3LqU

Any thoughts?

tehsiggi wrote on 2026-10-26, 06:49:

The overall topology appears to rely on finding a good, already done 12V PSU (AC/DC). Depending on how much power you need for t […]
Show full quote

The overall topology appears to rely on finding a good, already done 12V PSU (AC/DC). Depending on how much power you need for the system, it might be already a tough task to find one that fits well.
I suppose whenever you design a backplane for your “dead PSU” form factor (speaking of non ATX/AT) you’ll might have to jump for a different base PSU.

---

bitslasher wrote on 2026-10-26, 05:42:

The last part of your post is a little confusing. It almost sounds like something an AI would respond to a prompt about "A "+5V strong" ATX "set of PSU guts" -- what does that mean?

He basically appears to think about designing a ATX power supply board that is strong on the 5V rail to fit into existing modern ATX PSU housings. To get good 5V performance with reliable components, rather than refurbishing old PSUs.

Tons of 19.x volt laptop psus are made into waste every year, needing 12v specifically leaves a ton of donar equipment be it classic 19 volt barrel or USBC which could plug externally to fire up the internal PSU bits

rmay635703 wrote on 2026-10-31, 16:49:

tehsiggi wrote on 2026-10-26, 06:49:

The overall topology appears to rely on finding a good, already done 12V PSU (AC/DC). Depending on how much power you need for t […]
Show full quote

The overall topology appears to rely on finding a good, already done 12V PSU (AC/DC). Depending on how much power you need for the system, it might be already a tough task to find one that fits well.
I suppose whenever you design a backplane for your “dead PSU” form factor (speaking of non ATX/AT) you’ll might have to jump for a different base PSU.

---

bitslasher wrote on 2026-10-26, 05:42:

The last part of your post is a little confusing. It almost sounds like something an AI would respond to a prompt about "A "+5V strong" ATX "set of PSU guts" -- what does that mean?

He basically appears to think about designing a ATX power supply board that is strong on the 5V rail to fit into existing modern ATX PSU housings. To get good 5V performance with reliable components, rather than refurbishing old PSUs.

Tons of 19.x volt laptop psus are made into waste every year, needing 12v specifically leaves a ton of donar equipment be it classic 19 volt barrel or USBC which could plug externally to fire up the internal PSU bits

I repeat myself: My statement is based on what the OP has written. If he wants to keep the AC still going directly into the PC, I'd go with 12V as the base voltage of the AC/DC unit. Using an external power supply is a completely different story.

His project idea sounded like keeping the behavior of the original PSU the same while replacing the guts of it.

rmay635703 wrote on 2026-10-31, 16:49:

Tons of 19.x volt laptop psus are made into waste every year, needing 12v specifically leaves a ton of donar equipment be it classic 19 volt barrel or USBC which could plug externally to fire up the internal PSU bits

The median output of those is 65W though with a lot of lower 45, even 30W ones around now. It's getting difficult to find the 95 or over 125W ones from the "Desktop replacement, also Intel can't make a decent mobile" days.

Anyway, stick that through your 20% de-efficienciser to get 12V and you're down to worrying if you'll blow things up if you run more than 2 or 3 drives.

MikeSG wrote on 2026-10-29, 06:43:

Something like this would be ideal for a high expense/high safety angle. […]
Show full quote

Something like this would be ideal for a high expense/high safety angle.

MEAN WELL NMS-240-5. Input AC lines. Output 180W 5V 36A. Has every certification. $66USD
https://au.mouser.com/en/ProductDetail/MEAN-W … 5zXDDhlvA%3D%3D

There's a 12V module as well at a similar price, but two of those would mean the price starts at $133USD before PCB costs ($30-50), but there is practically nothing else remaining cost-wise because the modules do everything.

Those modules don't have a rectifier or filter cap, so they're DC input. The main chassis will contain the rectifier and PFC circuit.

Dropping that entire power supply into a case would be interesting (and expensive).

MikeSG wrote on 2026-10-29, 14:38:

For an OEM design, another issue is the cables. Is the user now tasked with cutting each cable at the old PSU internals, keeping track and inserting into a new connector or soldering... or are the cables pre-soldered and come with the new PCB, adding to cost.

That's another question. If you don't want the buyer to solder and they're replacing something proprietary, you could use common crimp terminals since the crimp tools will cost a lot less than the tools to install a full connector. Screw terminal blocks have lots of issues with loose connections or stripped screws if you aren't careful.

lti wrote on 2026-10-31, 19:35:

MikeSG wrote on 2026-10-29, 06:43:

Something like this would be ideal for a high expense/high safety angle. […]
Show full quote

Something like this would be ideal for a high expense/high safety angle.

MEAN WELL NMS-240-5. Input AC lines. Output 180W 5V 36A. Has every certification. $66USD
https://au.mouser.com/en/ProductDetail/MEAN-W … 5zXDDhlvA%3D%3D

There's a 12V module as well at a similar price, but two of those would mean the price starts at $133USD before PCB costs ($30-50), but there is practically nothing else remaining cost-wise because the modules do everything.

Those modules don't have a rectifier or filter cap, so they're DC input. The main chassis will contain the rectifier and PFC circuit.

Dropping that entire power supply into a case would be interesting (and expensive).

You're right I misread the module specs.

This is another, lower cost module at $15 USD. Board mount, 5v @ 10 Amp = 50W. There is a 12V module for the same price.
https://au.mouser.com/en/ProductDetail/MEAN-W … ew-254754677759

Not sure how much power is required, but could easily fit multiple and split power delivery.

Could be a sub $150 project with cables/connectors included, but there is going to be soldering somewhere if the original case is retained. There is still the fan and on/off switch.

adalbert wrote on 2026-10-28, 09:02:

Hi, I've been thinking about this issue on-and-off for a couple of years actually, and I just made a first working prototype of […]
Show full quote

Hi, I've been thinking about this issue on-and-off for a couple of years actually, and I just made a first working prototype of custom DC-DC PSU board, I posted this in another topic (AT(X)Anything: a modular DC-DC PSU for old PCs (open hardware)).

Basically it's a supervisor and power distribution board, which can be set up to work in AT or ATX mode, it generates 5VSB and -12V/-5V rails, has multi-stage OVP protection, and for 12V, 5V and 3.3V converters you can put anything you want through screw terminals, or solder smaller modules directly to the PCB. That should mitigate any supply chain issues, because the parts on supervisor board are common and easily available, and it is easy to change what kind of converter you want to use.

I designed it around 20V input, though it also could be scaled further, should work up to 24V with no changes (so USB-C PD 20V or 24V industrial bricks should work).

The attachment photo1.jpg is no longer available

Oh wow! That's amazing! Yes, so it seems like our ideas are almost identical! So my design is based on a 12V source, that should be equivalent of a 200W PSU. That seemed like a good starting point, allowing enough power to run some old hard drives if someone wanted.

My mindset was to not take on the risky/dangerous high voltage part, at least not at first. With the modularity of this design, any 12V AC/DC PSU can be used. But I've found that there are a category of PSU that's 4x2 inches square, and have a somewhat "standard" stand off locations. Here's a Mean Well LOP-200-12, priced around $50 and less, depending on source and quantity:

So you'd have a lead from that guy carrying the amped up 12V current to the DC 12V converter (connecting to that big green connector). The DC converter then has the +12/-12/+5/-5V legs coming off a 40-pin connector that plugs into the replacement PCB with the appropriate system-specific connectors on it.

kwyjibo wrote on 2026-10-31, 15:52:

I recently came across to this: […]
Show full quote

I recently came across to this:

https://github.com/neo-internalforce/ATX5Vbooster

From this video

https://youtu.be/BrJlWmi3LqU

Any thoughts?

This is very encouraging. His design works, so it shows me that home-brewing PSUs is possible. 😀 His design though plugs into the motherboard and is quite large. My design is trying to keep all that in the original PCB case. We'll see how it turns out. 😀 I may reach out to him for advice and help!

rmay635703 wrote on 2026-10-31, 16:49:

Tons of 19.x volt laptop psus are made into waste every year, needing 12v specifically leaves a ton of donar equipment be it classic 19 volt barrel or USBC which could plug externally to fire up the internal PSU bits

That's a valid point! I had originally considered this, but the lack of standardization around those power bricks discouraged me. The voltages, the amount of power they put out, the type of jack that it has... it's all over the place. I was attempting to at least at first come up with the simplest most generally useful components, like the DC converter part.

So the high-voltage part of the design at the moment is placed on a pre-made AC/DC 12V internally installable unit. There can be a variation of this design that can adapt to a barrel though. So let's say one could have in place of the AC/DC module another smaller module that adapts the 19V down to 12V? Then one could replace the C14 AC plug on original PSU with a 3D printed component that houses a barrel jack to accept the external PS.

Is there a way to make something that can auto-sense the incoming voltage and regulate it down to 12V? And as for the barrels, is there a "generic" barrel form factor that is easy to find adapters for?

bitslasher wrote on 2026-11-01, 17:00:

That's a valid point! I had originally considered this, but the lack of standardization around those power bricks discouraged m […]
Show full quote

rmay635703 wrote on 2026-10-31, 16:49:

Tons of 19.x volt laptop psus are made into waste every year, needing 12v specifically leaves a ton of donar equipment be it classic 19 volt barrel or USBC which could plug externally to fire up the internal PSU bits

That's a valid point! I had originally considered this, but the lack of standardization around those power bricks discouraged me. The voltages, the amount of power they put out, the type of jack that it has... it's all over the place. I was attempting to at least at first come up with the simplest most generally useful components, like the DC converter part.

So the high-voltage part of the design at the moment is placed on a pre-made AC/DC 12V internally installable unit. There can see a variation of this design that can adapt to a barrel though. So let's say one could have in place of the AC/DC module another smaller module that adapts the 19V down to 12V. Then one could replace the C14 AC plug on original PSU with a 3D printed component that houses a barrel jack to accept the external PS.

Is there a way to make something that can auto-sense the incoming voltage and regulate it down to 12V? And as for the barrels, is there a "generic" barrel form factor that is easy to find adapters for?

You have to consider complexity. If you want to be universal, it has it's price.

That's why I asked the questions on what you wanna achieve with the design. Internal or external power supply etc.

And if you want to "auto-detect" if the input are 19V instead of 12V, you'd have to have an additional step down from 19V to 12V.

If you consider this, you should directly chose 24V for the input voltage, even from the AC/DC part. Then using 19V instead is a breeze. You can then go from 24V to everything else.

For your design: I'd go with angled connectors so the module can stand vertically. This helps to use space more efficient.
Why would you go directly with the 12V into the module? Why not into the backplane and from there via the single connector to the DC/DC part?

Those pin headers are, depending on the manufacturer, rated with around 3A per pin. I'd not exceed 1,5A or 2A per pin.
Which then begs the question, how much output current do you want to transfer from the DC/DC boards per rail? 20A-30A per output voltage? (the 3.3V and 5V)
That would mean (if you go with 3A) up to 10pins per rail (when going for 30A) + 10 corresponding GND return pins per rail (because the current has to come back.

That doesn't leave much on the 40 pins.
What is your desired power rating? I've written a lot of questions in the previous posts for which we still seek answers 😉

Do you have some kicad files to review? some traces look interestingly thin 😁