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How would you replicate this PSU
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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:

--- Quote from: rthorntn on June 05, 2018, 08:28:34 am ---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.

--- End quote ---
Repairing faulty PSU  :palm:
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:

--- Quote from: rthorntn on June 05, 2018, 09:12:52 am ---It has 65% efficiency, I would like something fanless and a lot more efficient. 

--- End quote ---
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 There is nothing fundamentally outdated in this PSU, UC384x based PSUs are produced till this day.

--- Quote ---Over 90% is fairly normal nowadays?
--- End quote ---
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.

--- Quote ---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%.
--- End quote ---
:palm:
And then builds PSU based on toroidal transformer and buck converters with around 75% typical efficiency  |O. 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.
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