New FM Towns Tower power supply project

[mez]

it looks like same as a HR one
i have replaced my entire HR PSU with a (poor) Pico PSU + Arananet adapter. It works fine but yes I'm waiting for another CYO new project

[Cyothevile]

There are 3 different desktop power cards and they are DIFFERENT. Don't assume until you check the connector and specifically color order of wires. Towns for some reason like to mix up brown wires which have 12V and 5V.

I don't be making a power card for desktops. I learned a lot from the failed project though. Specifically there isn't a pico that outputs enough power on 5V rail. Fake/clone pico can output enough current in my tests but I can't recommend fake pico. I don't use fake pico those are shit.

I have been meaning to make a photo guide of ATX conversion and use my HR100 as the example. I've just been really busy with other projects but a clever person again can use my Arduino pro micro script and a flexATX, taken out of its case and fit it inside the stock desktops PSU case. It's the same Arduino code that works perfect on the tower models. I must say though a flexATX won't fit inside a Pentium desktop.

[kamiboy]

How much power does the towns desktops need on the 5V rail?

[Cyothevile]

How much power does the towns desktops need on the 5V rail?

There are so many different ones I didn't even attempt to lock onto that.

[Cyothevile]

I have updated the Tower card and added mounting holes specifically for using a slightly cheaper AC/DC converter such as the EPS-120-12.  Any converter in a 2x4 (inches) form factor will fit.  Also reposition it closer to AC cable. 

I still need to verify the measurements of the original card (which I don't have anymore RIP) specifically the screw holes.  Heard a report here and one other spot that it's troublesome and filing the holes was required.  If anyone here would like to give me a dead tower PSU out of charity I would appreciate it.

https://github.com/cyo-the-vile/FMT-ATX-TOWER

I will update it one more time in a few weeks and have a store online to sell some cards.

If there is demand for a GEN1 card I will revisit that.

Update: Modified Gen 1 card requirements and sizing.  Now the card is 2 layer but requires expensive ACDC converter. Untested. If you plan to use this I can help in the assembly via DMs so you don't fry the pc

[UnbornApple]

Thanks for sharing all of this. My CX20 worked beautifully for a few hours after I recapped it. Then the next day it would no longer turn on, and I found a toasted resistor on the power supply. I'm going to order all of the parts and give this a try.

[amazin]

Update: Modified Gen 1 card requirements and sizing.  Now the card is 2 layer but requires expensive ACDC converter. Untested. If you plan to use this I can help in the assembly via DMs so you don't fry the pc

Hey Cyo!

I've had your (updated) Gen1 card made at JLCPCB, I have a PicoPSU (original) and a Meanwell 12V ACDC that I've already used before successfully on X68000s.



I'll be following your guide here:
https://ascendance.systems/2021/06/01/fm-towns-power-supply-generation-1/

Do you have anything to add other than the post above and github?

Thanks in advance

[amazin]

Gen1 PSU (almost) fully built. Triple-checked the pins on the Centronics-14 connector to the motherboard.



Just waiting for the Arduino Pro Micro (I had several Minis, no Micros) to arrive tomorrow, program it, and see how it goes. So far so good.

Cheers

[opooly]

Hi all,

I m looking to order 5 board to build a PSU for my FMT 2F in the coming days, if anyone is having spare board please let me know, I m happy to buy it

[kamiboy]

I have updated the Tower card and added mounting holes specifically for using a slightly cheaper AC/DC converter such as the EPS-120-12.  Any converter in a 2x4 (inches) form factor will fit.  Also reposition it closer to AC cable. 

I still need to verify the measurements of the original card (which I don't have anymore RIP) specifically the screw holes.  Heard a report here and one other spot that it's troublesome and filing the holes was required.  If anyone here would like to give me a dead tower PSU out of charity I would appreciate it.

https://github.com/cyo-the-vile/FMT-ATX-TOWER

I will update it one more time in a few weeks and have a store online to sell some cards.

If there is demand for a GEN1 card I will revisit that.

Update: Modified Gen 1 card requirements and sizing.  Now the card is 2 layer but requires expensive ACDC converter. Untested. If you plan to use this I can help in the assembly via DMs so you don't fry the pc

I downloaded your Kicad files and made some modifications for a custom version of the PSU for my own use. I decided to use the Meanwell RM-90-12 AC/DC converter, which is only 80Watt and swapped the Arduino for an Attiny85. The reasons for the changes are not exactly what I would call, rational, but it is more of an experiment anyway.

I originally wanted a ATtiny4 since it has the fewest number of input/output pins but I don't think that series can be programmed using Aruduino code and I wasn't keen on trying to figure out how to code for it. There is no benefit to using an ATtiny really, but I feel an Arduino is a bit overkill for just on/off functionality. I actually wanted to see if I could make the on/off circuit using old fashioned IC's such as flip flops and and gates, but after a bit of research I think that would have been too much work to get the same functionality.

The RM-90-12 is quite cheap, but I want it mainly because it is a neat self contained module. I originally wanted to just circumvent the AC/DC + PICO combo and use several TRACO modules plus the optocoupler from the original PSU, but the cost would have been very high.

80W might be too little for what the TOWNS might pull out of the PICO, though...

Anyway, I'll report back how things go.

[kamiboy]

Well, I think I am just about done with the modifications. I decided to repurpose the relay to enable the switching on/off of the power output port from my 20F PSU.

However, that should obviously not be used when connecting to 220V so I added a jumper to disable the relay functionality.

I also incorporated the fuse and three input filter caps that were connected to the voltage input from the old board. Not sure they do anything useful on this modern system, but hey, they are optional, so they can be skipped.

I also added in the three screw holes in the middle of the board. I am certain my measurements will be off by a bit and some things are likely not optimally placed, but I think getting it right on the first try is not realistic. I'll try to order a print and see what happens.

[kamiboy]

I got the idea to print out the PCB layout and see how things lined up. To my surprise the board width seemed to be off by 2 mm on one side, which is fine, but all the screw holes also seemed off by degrees.

Now, I am not 100% sure I can trust the print, but after careful measuring of the board I am convinced that the print is an accurate representation of where things will go on the PCB. So I just repeatedly adjusted the screw holes and printed out the results for comparison. After 10 or so iterations I think I have them more or less dialled in now.

There are these metal pegs that the PCM falls into and the tolerances there are quite tight, of they don't light up exactly I think the PCB won't go into place. Additionally the alignment of the exit port is very crucial, and on my model it slides into place and I think the pins need to align up exactly or it prolly won't slot into place.

Can anyone with a later revision tower PCB attest to how well the screw holes, metal pegs etc. lined up in their case?

Some early responses mentioned needing to file down holes, but I am wondering whether my adjustments are just screwing up an already perfectly dialled in placement or not.

Seems getting the mounting hole placements right might be quite tricky...

[Cyothevile]

I got the idea to print out the PCB layout and see how things lined up. To my surprise the board width seemed to be off by 2 mm on one side, which is fine, but all the screw holes also seemed off by degrees.

Now, I am not 100% sure I can trust the print, but after careful measuring of the board I am convinced that the print is an accurate representation of where things will go on the PCB. So I just repeatedly adjusted the screw holes and printed out the results for comparison. After 10 or so iterations I think I have them more or less dialled in now.

There are these metal pegs that the PCM falls into and the tolerances there are quite tight, of they don't light up exactly I think the PCB won't go into place. Additionally the alignment of the exit port is very crucial, and on my model it slides into place and I think the pins need to align up exactly or it prolly won't slot into place.

Can anyone with a later revision tower PCB attest to how well the screw holes, metal pegs etc. lined up in their case?

Some early responses mentioned needing to file down holes, but I am wondering whether my adjustments are just screwing up an already perfectly dialled in placement or not.

Seems getting the mounting hole placements right might be quite tricky...

Those mounting hole placements are an extreme pain in the ass and I never got it right. Optimally, you would want to desolder every single component on the PSU card and scan it. Upload it as a graphic in kicad and move the mounting holes accordingly. Me using a caliper isnt perfect as usually only ~4 mounting screws work properly and sanely.
If you do end up making a sane card that has mounting holes that arent insane please push a commit so I can update it.

[kamiboy]

I did get the metal post locations more or less correct, except for one which ended up being off by a millimetre. Luckily the metal posts on my housing can be bent a bit to make them fit, which I did and fit it did.

I have soldered just about everything in but have yet to actually test the PSU as I need to find a way to program the ATtiny85 with the Arduino code. I have a USB programmer but it seems to require a Windows machine to work, which I do not have nor can access at the moment.

In any regards, I won't upload my modified files to the GitHub repository as I did the modifications in a haphazard way because I was not familiar with the software. So I am afraid I might break something if they are just uploaded as is. However, the files are attached here to do with as you please. Perhaps you can copy over the post locations from it.