How would you replicate this PSU - Page 1
Forum section: electronics / beginners

author: rthorntn
author_rank: Frequent Contributor
timestamp: June 05, 2018, 08:28:34 am
content: 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 - 0.3AJust 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.htmlThe only thing interesting on this PSU is it has a "power good" signal, I guess that would have to be replicated.Thanks for looking.CheersRichard

author: wraper
author_rank: Unknown
timestamp: June 05, 2018, 08:54:49 am
content: Quote from: rthorntn on June 05, 2018, 08:28:34 amRepairing faulty PSU

author: rthorntn
author_rank: Frequent Contributor
timestamp: June 05, 2018, 09:12:52 am
content: 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?

author: wraper
author_rank: Unknown
timestamp: June 05, 2018, 09:31:38 am
content: Quote from: rthorntn on June 05, 2018, 09:12:52 amIf 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 There is nothing fundamentally outdated in this PSU, UC384x based PSUs are produced till this day.QuoteOnly if you buy something like 80+ titanium rated ATX PSU.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.QuoteAnd then builds PSU based on toroidal transformer and buck converters with around 75% typical efficiency. What an upgrade, my ass.

author: james_s
author_rank: Super Contributor
timestamp: June 05, 2018, 06:06:23 pm
content: 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.

author: JS
author_rank: Frequent Contributor
timestamp: June 05, 2018, 07:50:10 pm
content: Quote from: rthorntn on June 05, 2018, 08:28:34 amWhat 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

author: wraper
author_rank: Unknown
timestamp: June 05, 2018, 07:51:19 pm
content: Quote from: james_s on June 05, 2018, 06:06:23 pmOnly if some really old (relatively low efficiency) crap. Modern ATX PSUs don't have -5V.

author: james_s
author_rank: Super Contributor
timestamp: June 05, 2018, 08:34:58 pm
content: 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.

author: CJay
author_rank: Super Contributor
timestamp: June 05, 2018, 08:38:14 pm
content: Quote from: james_s on June 05, 2018, 08:34:58 pmAbsolutely, repair the original if possible, they're ridiculously simple supplies

author: stj
author_rank: Super Contributor
timestamp: June 05, 2018, 09:51:17 pm
content: an arcade psu could do it, they are 5v 12A, 12v 2-3A, -5v 1athe -5 is usually from a 7905 regulator fed with -12 or -15vbut just fix the original - it's not worth bitching about efficiency over something only running a few A