FM Towns PSU

[caius]

I successfully replaced the PSU in my FM-TOWNS II MX with a standard ATX :

https://www.youtube.com/watch?v=87RLYVn58A4&feature=youtu.be

The adaption was easy, I quickly figured out the pinout of the connector on motherboard (16PIN molex but it can differs in other FM-TOWNS models).
The voltages needed (+5V, +12V, -12V) for powering the FM-TOWNS are present on a ATX PSU along with the +5VSB but colors of wires of the FM-TOWNS PSU mean different voltages compared to ATX.This is the adaption diagram valid for all FM-TOWNS models (but check always with a multimeter)

BLACK=GND ---------------------->same of ATX
BROWN=+5V---------------------->RED ON ATX
RED=+12V------------------------->YELLOW on ATX
ORANGE=-12V--------------------->BLUE on ATX
YELLOW=+5VSB------------------->PURPLE on ATX

On the FM-TOWNS PSU there is also a white wire, this seems to be connected (but not used) to the rear fan connector, we can omit it in this adaption.
As said, the original power switch cannot be used since the FM-TOWNS power up works in a different way, specifically the original switch is a momentary one which briefly shorts the PS-ON signal (BLUE wire on the FM-TOWNS PSU) to GND.So you have to install a simple ON/OFF switch that keeps shorted to GND the PS-ON signal of the ATX PSU (GREEN wire) for the time the PSU must be ON.Here's a picture :




I hope this can help you all to replace your faulty FM-TOWNS PSU.If you have any question, don't hesitate to ask.

[kamiboy]

Great work documenting this stuff. With how rickety Towns PSU's are I am sure this will be of great use to many.

[Tw3ek]

Tested this today with a previously broken FM Towns unit and it once again powers on. Thanks so much caius for the work and the help!

[caius]

Thanks to you for your feedback.In the next days I will post a more detailed tutorial on www.jammarcade.net

[famiac]

Cracked a couple of power supplies open and found that the notorious IC51 appears to be labeled on one of them.

Here's a photo:


Here's the datasheet

[caius]

Very good find.

[gypsie]

Hello Caius,

Do you have more picture of your ATX psu modification please ?

[caius]

Hello Caius,

Do you have more picture of your ATX psu modification please ?

Sorry for late reply.No, I have no futher pictures of this modification.Anyway, I posted the connection diagram, you can't go wrong if you follow it.The only difference could be different cloors of wires in your FM-TOWNS PSU especially if you have a differerent FM-TOWNS PC model.As for colors of the ATX PSU, they are standard and don't change.

[gypsie]

ok thank!

I m trying to repair the original psu from FMT II HR.

Symptoms :

Shutdown 10 sec after the first power up.
After the first shutdown, the FMT can't stay "on" more than 1-2 sec.

I ve opened the psu, very good condition inside ( no dead diode,resitor etc..). I will change the capacitors to start.

[hungar]

Hi all Im trying to get to the power supply on my FMT II tower(2f) I can get all external plastic panels off and the main metal chasis but for the live of me I can't seem to get the main board out to reach the PSU  ( outside of a hammer ) has anyone done this before?

[gypsie]

I ve replaced the psu on my FMT 2HR with an ATX one. Sadly, computer boots fine but can't open the cdrom drive ( nothing happen when pushing the open/close button).

I don't understand, i ve checked all the wires.

Need some help please...

[caius]

CD drive tray should need 12V for proper operation so my advice is to check if they are present.

[gypsie]

Hello Caius,

Yes i will check the 12v on cd drive, i will put result on this topic.

Thank for your reply Caius

[raizing77]

Hi
I have same problem
when I press the cd rom button I hear a click but it does not open

I tried to insert a CD but it does not turn .... it seems without power

the cd rom before the breaking of the psu worked

I tried to change capacitors and the nec integrated c1099 but this is not the problem

some ideas to work the original psu.

or how to give power to the cd rom


Thx

[mattsoft]

Was anyone able to figure out the pinout of the PSU on this model? If so, could you please post? Thanks!

[Jehuty]

Diggin old topics - but i now have a FM Towns II (Model CX20) too
On mine the PSU was completeley dead - after some Recap and fixing some Resistors its back to life.
But if i conect the powerplug in the FMT starts immediatley - the Powerbutton on the front doesnt do anything.
Measured the Vootages are 12V, 5V, -12V on the connector. And there are two other Pins - both have the 12V and one of them goes to 0V if i press the powerbutton. So i think the fault why the fmt doesnt power off is on the psu.
Checked the Transistor but they are ok so it could be that "Mysterious" IC51.
But the IC isn´t so mysterious if you desolder it - the name is printed on the PCB :-)



So my quastion could the IC be the fault ? i desoldered it, but i have no spare part, not yet.

Another question - if i build a atx PSU - there are Voltage Pins on the mainboard - could these be used to power up the system ?

[Jehuty]

No it wasn´t the IC51. Replaced it but doesen´t change anything.
And meanwhile it doesn´t power on at all.
One evening played a little bit arround with the FMT and turned it off (Plug)
Next day nothing - no power up. On the 2 Pins down one has 12 V the other nothing.
Seems that it is now comlpetly dead. But i have replaced it now with an ATX.

[Jehuty]

FYI - i replaced the PSU with a ATX and an ATX adapter normaly used for Amiga computers.
You just need a method to switch a ATX PSU with a momentary switch and you could use the 2 Pins to
Power on the FM Towns with the switch and Softpower from Software.

[cageman]

I just received a defective FM Towns II (CX20). I already own a working one, but will be troubleshooting this one's power supply. I'll try to determine the pinout of the large connector and document it (here?).

I hope the current PSU can be resurrected

[Jehuty]

From one side the first (i think, not sure) 14 are +5V - then 5 Pins are 12V, one Pin (the single pin) is -12V then come GND until the last (Pin 43 + 44) both. They are Power On/off from switch and the other from software.
I use a ATX adapter, normaly designed for Amiga, with the momentary switch method on these both last pins. So i can Power On / Off via the Switch on the front and when i shutdown TownsOS it also powers off.

[mez]

if nothing happens after re-caping and re-resistoring then PICO PSU could do the job







fitted inside

[Cyothevile]

if nothing happens after re-caping and re-resistoring then PICO PSU could do the job







fitted inside

Two questions:

Do you require adding a second switch?

Are you still able to perform software shutdown in TownsOS with that power supply?

[mez]

1° Yes
2° Didn't try but sure No

[Jehuty]

A solution is in my posting before.