New FM Towns Tower power supply project

Started by Cyothevile, January 06, 2021, 01:07:42 AM

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I have made some progress with a Tower power supply replacement. The 44 pin connector is not proprietary and is a modern sourceable part and it's still manufactured. The design will be open sourced once it works and I have a reseller willing to sell them once working so people can get them. The end state is a beginner level soldering installable replacement for these computers. We know those tower PSUs are a pain even after a recap they seem to die. This has happened to me twice.

At this time my board simply functions as an ATX adaptor where you need the second switch in the back for it to function. However I'm exploring circuits at this time to turn the PSU on with the original power button and an operating system shutdown function through townsOS. This would place this PSU as a direct 1:1 replacement in terms of functionality.

A shorter version without the 12V DC converter is also possible if you can fit an ATX inside the original metal shielding. For the 220V countries this means you won't require a step down converter.

Attached is photo of my current board. The circuit onboard doesn't work. I have the proper pin out for the 44 pin backplane connector and the computer does turn on if you force the power on. However the original power button isn't working to turn it on. I attempted a latching circuit and unfortunately it isn't enough. I'll be attempting a new circuit later this week.

For those with electrical engineering experience I would love some input with this. If this project is completed a solution can be made for the desktops as well with the same circuit if it works for towers. Towns seems to use two different power supplies all together.


Great Project.

I managed to use the powerbutton and softpower via an ATX Adapter designed by Ian Steadman for Amiga Computer.
The lower 2 pins from the 44 pin connector are for that. One ist power button the other softpower. I mean they switch to GND. I use the Ian Steadman adapter with momentary so the power switch works.
Can you use this circuit on your PCB ?



Quote from: Jehuty on January 06, 2021, 05:56:07 PMGreat Project.

I managed to use the powerbutton and softpower via an ATX Adapter designed by Ian Steadman for Amiga Computer.
The lower 2 pins from the 44 pin connector are for that. One ist power button the other softpower. I mean they switch to GND. I use the Ian Steadman adapter with momentary so the power switch works.
Can you use this circuit on your PCB ?

I tried it a while back but haven't revisited. I think I was programming MCU incorrectly. I should get parts this week to try a different circuit. If it doesn't work I will revisit that one


looking good so far, and very cool that you are doing something like this!


Leyline power supply board seems to work as untended so far... Well it passes LED test. So I will try to add it into a dead HR100 that arrives at my house soon. If it works the circuit can be exported for use for the tower models also. This PSU card works for all Desktops to include HG, HR, MA, MX, ME and Fresh models. It won't work with HA family of parts Pentium series and won't work with FMV as I don't own these PC to test them.

It takes some inspiration from mattsoft's project for X68 where it uses ACDC converter and pico. I made an on board circuit so you can keep use of original power button. I also added connector for noctua fan and stock fan. Has 5Vstandby LED and power-good LED indicating it turns on when the on-off line hits ground... Or when you push power button on front of the PC. I believe it should work but I'll test in a few days/weeks on my dead HR100. This will also work for 220V countries as the ACDC converter I used is 220V compliant as well.

Following the BEEP Magazine scans of the power wire pin outside, you cut the wires from your Dead PSU and use block terminal which is clearly labeled. I would personally recommend just soldering the wires without block terminal but I will test both before releasing this. I find this better than the ATX wiring methods. 

It's very expensive to assemble and I won't be selling this as I only made it for a few friends of mine. However it will be open source and I will include assembly instructions that must be VERY carefully followed and bill of material. The only stock functionality that isn't implemented is operating system shutdown funtion when you select power off in townsOS and you will lose functionality of the power receptable in the back. However for most users it shouldnt be an issue.

I think more people want to see tower PSU card more :)


April 03, 2021, 04:11:31 AM #6 Last Edit: April 13, 2021, 11:26:26 AM by Cyothevile

I have finally made a PSU that keeps the integrity of the original power button.  I added noctua connector to tower and desktop PSUs.  I tested the script with my Arduino on my HG/HR and plan to replace all my Towns PC with this PSU I designed.  I personally cannot stand that 12V standby that wrecks these 30 year old ICs and diodes hanging by a thread. Fits almost all desktop except I can't verify FMV Towns.

I'm sending to fabrication for final testing before releasing this into the wild for everyone to use and it will be on my github.  For the Desktop PSU you need to cut the wires from your dead power supply and then solder them to the new card.  Follow the BEEP manual scans I posted a few months ago and you will be fine.

I also added connection for "TownsOS power off" function if someone wants to program Arduino later on to add that feature.  My script doesn't have it implemented because I can't be asked.... I believe 99.999% of people don't really care though :p

Also this is 220V and 120V compliant because I use the Meanwell EPS-120-12.


Oh quick update.
The script is updated and it can now turn off via TownsOS. So this is true 1:1 replacement. I would highly advise at this point to consider throw your 30 year old PSU in trash.

Give me a week or two to final test new boards when they arrive.



Just joined this forum for this great initiative.

I have an FM Towns 2F sitting on my desk that had a dead PSU, although I had changed all the capacitors, before the PSU died some hours of use later.

Jehuty has supported me in connecting an external ATX PSU to the original PSU board, but this is far from original and requires a lot of space on the desk - plus complete immobility of the entire system.

I am hoping to get one of your new PCBs.

Good luck.


The Tower PSU card 100% works turning on and off. I'm sending it to my tester for final stress testing.

Provided it works fine as it should I will have 3 left for sale without ACDC converter and pico PSU. $40 before shipping. After that the tower PSU bill of material and board files will go to GitHub for everyone to use. I will also try to get an eBay seller to have some in stock eventually

Arduino controls the power supply on and off button as it runs on 5V standby from the pico PSU. It also can perform TownsOS power off function when you select it in TownsOS.


And again like all things one more revision is needed. Well I want to get screw holes perfect. Here is few photo of tower PSU test unit. I ordered 50 PCB with slight adjustment and I will hand assemble. The final material cost to include pico and ACDC converter is $95 USD and only that low because I buy in bulk. This was very long on and off project of mine but it's finally coming to a close. It uses high quality components no fake pico to destroy Ricoh sound chip :)

If anyone wants to buy it's $140 shipped in USA. I'm not sure price to ship to friends in Europe but I will take a look later.
Hopefully people can appreciate the time, testing, R&D it took for me to make this. I will have installation guide later for it also. Only 4 wires are required for soldering. The only difference between this card and stock card is that it is 86-286VAC compliant (yes for you 220V country you don't need step down) and receptable in the back is based on your country power. So if you're in Europe don't connect FMT monitor to that receptable. You have been warned.

Here is some photo from test card.

It was tested running super street fighter 2 for 24 hours. Floppy drives work find also and hard drive loading also works fine from my tester and myself. Double goteks inside CX20 also work fine. Wizard ODE also work fine.

Desktop revision card is also coming from factory next week. It fits inside HG/HR and EA type desktop metal shields. It should also fit inside the desktop between those (4 expansion slot type). Won't work for Pentium towns or FMV. Unless someone want to sell me HC53M Pentium to study and make something. Everyone this is now your chance to let me know you want it because BEEP store.... I don't know what their markup is going to be.


Please check it.

I have a few fully assembled cards.  Assembled, cleaned and tested ready to ship.  It's 140 USD shipped in USA.  Overseas I think is only $20 more and don't worry about VAT.

Still working on porting this concept to desktop card.  So far desktop card plays FDD and sound totally fine.  It won't load hard drive or CD ROM at all.  So have to troubleshoot that.


My 20F has a PSU rated at 90W. But do you know the wattage load distribution of this 90W is on each of the three power outputs (5V, +12V,-12V) from the PSU?


Quote from: kamiboy on May 12, 2021, 12:03:22 AMMy 20F has a PSU rated at 90W. But do you know the wattage load distribution of this 90W is on each of the three power outputs (5V, +12V,-12V) from the PSU?

All towers are 90 watt.

You can check the manual for ITX PSU from the website.  It's enough amps to drive everything.


I bought a model 2 (gen 1) tower to see if my card can work.

It can't.
However I'll design something that can fit inside the metal shield. Connector is totally different but it can be recycled into a new card.


Generation 1 card is done. Surprised I nailed it first time. Well a few holes don't line up 100% but that is trivial to correct.

Anyway it works in my MODEL2 perfectly which had a dead card inside it. Of course I have learned my CD Rom drive laser is trash and barely (mostly doesn't) read pressed CD.

Anyway I have 4 more of these PCB and they were expensive since they're very large. If you need any just message me.

Still working on desktop card