How would you replicate this PSU

[rthorntn]

Hi,

Would really appreciate some advice.

I have a failed Phihong PSM-5341, basically I want to build a modern replacement.

https://www.exxoshost.co.uk/atari/last/psu/PSM_5341_MegaSTE-TT030_PSU.pdf

+5V - 7.0A
+12 - 2.0A
-5V - 0.4A
-12V - 0.3A

Just spitballing... I could take say a standard AC/DC fixed voltage PSU, I would only need around 3A at 24V and convert it down, or maybe get two 30W dual output (5v/12v) to get the negative voltages?

People are replacing them with power brick + Pico-PSU + a little -5V converter thing from a guy in the UK called Ian, there has to be a nicer way.

http://www.ianstedman.co.uk/Amiga/designs/Amiga_ATX_Adaptor/amiga_atx_adaptor.html

The only thing interesting on this PSU is it has a "power good" signal, I guess that would have to be replicated.

Thanks for looking.

Cheers
Richard

[wraper]

People are replacing them with power brick + Pico-PSU + a little -5V converter thing from a guy in the UK called Ian, there has to be a nicer way.

Repairing faulty PSU 

[rthorntn]

Thanks, it has 65% efficiency, I would like something fanless and a lot more efficient.  Over 90% is fairly normal nowadays?

A side question can I damage a PSU like this one if I tested it without applying it a load?  The readings would be off but can you kill the PSU, some web pages are saying it's bad?

[wraper]

It has 65% efficiency, I would like something fanless and a lot more efficient. 

If you slap together that crap, I doubt you'll get much better efficiency. There is nothing fundamentally outdated in this PSU, UC384x based PSUs are produced till this day.

Over 90% is fairly normal nowadays?

Only if you buy something like 80+ titanium rated ATX PSU. And it's still won't be in a full load range. Not to say it's ridiculous to seek power savings in something like this.
If you want to replace it based on reading this: https://www.exxoshost.co.uk/atari/last/psu/index.htm, then you should know that autor is an idiot as he estimates efficiency based on BS assumptions.

Looking at a Phihong switchmode of 240V 0.6A input is 144watts input. The maxium output wattage is stated as 39watts. This would yelid a efficiency of about 56%.

And then builds PSU based on toroidal transformer and buck converters with around 75% typical efficiency  . What an upgrade, my ass.

[james_s]

You won't reasonably be able to build something that works any better. Would an off the shelf micro ATX PSU fit?

Personally I would repair the original, I like to keep vintage gear as original as possible, efficiency is not really an issue since it's not like you're likely to be using a vintage PC daily.

[JS]

Hi,

Would really appreciate some advice.

I have a failed Phihong PSM-5341, basically I want to build a modern replacement.

https://www.exxoshost.co.uk/atari/last/psu/PSM_5341_MegaSTE-TT030_PSU.pdf

+5V - 7.0A
+12 - 2.0A
-5V - 0.4A
-12V - 0.3A

Just spitballing... I could take say a standard AC/DC fixed voltage PSU, I would only need around 3A at 24V and convert it down, or maybe get two 30W dual output (5v/12v) to get the negative voltages?

People are replacing them with power brick + Pico-PSU + a little -5V converter thing from a guy in the UK called Ian, there has to be a nicer way.

http://www.ianstedman.co.uk/Amiga/designs/Amiga_ATX_Adaptor/amiga_atx_adaptor.html

The only thing interesting on this PSU is it has a "power good" signal, I guess that would have to be replicated.

Thanks for looking.

Cheers
Richard

What kind of solution are you trying to get with this? beter, more efficent and reliable? cheaper? easy to get up and running?
What about getting a PC PSU, many options out there, from brand new to some AT you can find in the dumpster, that would cover your need without much effort I guess.

JS

[wraper]

Would an off the shelf micro ATX PSU fit?

Only if some really old (relatively low efficiency) crap. Modern ATX PSUs don't have -5V.

[james_s]

Hmm good point. Well there are certainly plenty of power supplies out there with +/- 5V and 12V, and if you have one that has -12V it's easy enough to get -5V.

I would still just repair the original if possible though.

[CJay]

Hmm good point. Well there are certainly plenty of power supplies out there with +/- 5V and 12V, and if you have one that has -12V it's easy enough to get -5V.

I would still just repair the original if possible though.

Absolutely, repair the original if possible, they're ridiculously simple supplies

[stj]

an arcade psu could do it, they are 5v 12A, 12v 2-3A, -5v 1a
the -5 is usually from a 7905 regulator fed with -12 or -15v

but just fix the original - it's not worth bitching about efficiency over something only running a few A