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 Post subject: fm towns Marty universal PSU
PostPosted: Wed May 20, 2020 5:56 pm 



Joined: 30 Jun 2017
Posts: 27
Location: The Netherlands
Howdy!

For my fm towns Marty I am trying to work on its power supply (Tamura version!!!).

Since I have to wait for my replacement ELCO's for quite some time I decided to try and unravel the schematics for it (I think they don't exist on the web)

Here they are... I was wondering if some PSU gurus could take a look at them since I am not sure they are entirely correct :-)
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Furthermore... I decided to get crazy, remove all components and scan the empty PSU pcb. This way I can use it's dimensions to create a pcb in Eagle that uses the original on/off switch, AC mains input and metal bracket but has modern power Modules installed on it. In theory we could have a "drop in" PSU without the need to cut into the case.

Solder side
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Component side
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Curious to see what you guys think. I'll make the Eagle file public as soon as they're done :-)

Cheerz!


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 Post subject: Re: fm towns Marty universal PSU
PostPosted: Wed May 20, 2020 7:18 pm 



Joined: 04 Sep 2010
Posts: 1812
Location: Denmark
Neat, I am a fan of clean drop in PSU replacements like this for vintage Japanese computer systems. Someone did a similar thing for the X68000 as well. While both my machines work well after I replaced their caps, it is nice to know there are neat alternatives to resort to in the future if need be.

Always makes me sad to see a laptop adapter hanging out of a system that originally came with an internal PSU. Especially if getting the whole wonky thing to work the owner had to hack things apart, leaving a general mess.


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 Post subject: Re: fm towns Marty universal PSU
PostPosted: Sat May 23, 2020 5:44 pm 



Joined: 30 Jun 2017
Posts: 27
Location: The Netherlands
Here is what I have so far.

The power switch, AC input and metal bracket will need to be stripped from the original PSU, unless I can source them. Even though the power modules have their own build in protection I decided to go with a fuse anyway. Wouldn't feel good without it. Also added some caps on the output lines to filter a bit more ripple away.

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 Post subject: Re: fm towns Marty universal PSU
PostPosted: Sun May 24, 2020 3:20 pm 



Joined: 04 Sep 2010
Posts: 1812
Location: Denmark
I suppose that since the Marty is just a FM Towns386SX PC in a smaller box this replacement PSU design should be relatively easily translated to work in regular FM Towns computers as well. They have really dodgy PSU’s, let me tell you.

The form factor would be different but I imagine the output voltages and general functionality should be the same.


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 Post subject: Re: fm towns Marty universal PSU
PostPosted: Sun May 24, 2020 3:47 pm 



Joined: 30 Jun 2017
Posts: 27
Location: The Netherlands
kamiboy wrote:
I suppose that since the Marty is just a FM Towns386SX PC in a smaller box this replacement PSU design should be relatively easily translated to work in regular FM Towns computers as well. They have really dodgy PSU’s, let me tell you.

The form factor would be different but I imagine the output voltages and general functionality should be the same.


I don't think the output voltages are thesame. I have no experience with the FM towns PC's, but from the little info I read they require +5V, +12V and -12V. The marty is on +5V, +9V and -9V. Not that it is harder to create those voltages since it is a matter of putting on the appropriate power modules. Creating the dimensions of the board is easy enough. My main motivation was the fact that this machine was designed for Japanese voltages. I'm on 230V here, so with the re-use of some of the original components the idea is that the outside of the console is unchanged while I will still be able to directly connect it to the mains without a stepdown transformer :-)


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 Post subject: Re: fm towns Marty universal PSU
PostPosted: Tue Jun 02, 2020 8:32 pm 



Joined: 30 Jun 2017
Posts: 27
Location: The Netherlands
I made some progress on the Marty uni psu. As you can see, this is what it became. Unfortunately it did not revive my Marty and I will have to resort to reflowing as my next step to get my unit workin again. As soon as I can verify that this psu works I can upload files and part numbers. As you can see it is a non invasive, fully reversable mod.

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