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Old 18 April 2019, 17:24   #1
ItsTheSmell
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new psu

Im looking for recommendations for a new psu for my accelerated A1200. From an engineering point of view it needs to be as good as an original psu but with new components. Its surprising you cant buy new oem ones given most of the Commodore engineers are still around.
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Old 18 April 2019, 17:31   #2
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I don't know if Commodore designed many of their own power supplies in the first place... usually such things are outsourced to manufacturers specializing in that field.

In any case, Amigas just need a rather common +5/+12/-12 power supply, there are plenty of those around. For reusing an existing power supply housing one of the MeanWell models is a common choice.

If you need a lot of power, an ATX supply can also be used, although they are generally larger in size of course.
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Old 18 April 2019, 17:55   #3
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I dont feel safe using an atx psu.
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Old 18 April 2019, 19:23   #4
gdonner
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It's a U.S.-made PSU, but eBay seller commodore4ever makes quite nice, brand new PSUs that work with the A500, A600, and A1200:

https://www.ebay.com/itm/COMMODORE-A...UAAOSwz8NbfxbW

He does a nice job with them--owned one that worked fine with my A600 until I sold the A600 to buy an A4000.

I asked him if he would consider building a new power supply for the A4000--not sure if it's ultimately something he could recoup his time and money from, but even if he could make a caseless, populated drop-in PCB "guts" replacement, it could be quite welcome.

Last edited by gdonner; 18 April 2019 at 19:31.
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Old 18 April 2019, 19:53   #5
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I haven't tried one yet, but amigastore.eu has replacement power supplies that appear to look fairly good.
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Old 18 April 2019, 20:03   #6
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Will a picoPSU not suffice?
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Old 18 April 2019, 20:29   #7
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http://eab.abime.net/showthread.php?t=96925
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Old 18 April 2019, 21:53   #8
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A PicoPSU is only really of value if you need its small size. As mentioned, industrial modules from the likes of Mean Well and Artesyn will be cheaper and more capable than a PicoPSU, as well as not requiring the extra power brick. They can typically be fitted in the original PSU case too.
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Old 18 April 2019, 22:46   #9
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I've been advised that the MeanWell ones don't have a sense wire to monitor voltage drop in the cable. They'll work, for a while, but long term they are not advised from an engineering point of view.
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Old 19 April 2019, 01:00   #10
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Post

There are a few things you might want to consider. First of all, are you up to the task of handling conductors that carry potentially lethal currents? If not, please buy a ready-made PSU in a proper enclosure.

With that out of the way, there are numerous option available.
Having tried most of them, I'd recommend a factory made PSU module, be it in a cage or open frame.

Don't worry too much about about sense wires, your Amiga will run perfectly fine even if the 5V is a couple of tenths off. Do mind however, that you get a original MeanWell or Artesyn (or whatever you feel you can afford) unit, and stay away from those fleabay/aliexpress too-cheap-to-be-true offers.

I have had great experience lately using a device from XP Power, called ECM60UT31. You can find it at many of the large components distributors, I buy mine from DigiKey.
Modern PSU units (often) follow an industry standard for mounting holes, etc. that wasn't available 30 years ago. To overcome that, I have made STL files for printing mounting adaptors for both the large commodore PSU boxes (3 variants) as for the smaller/narrow ones (1 option). The 60W max power will ensure it doesn't melt the casing, as it did when I built a 100W Artesyn unit into a small A600-box. That didn't go too well...

PM me if you want the STL files. Eventually I'll post them to GrabCAD, just haven't got around to do that yet.
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Old 19 April 2019, 08:14   #11
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Quote:
Originally Posted by ItsTheSmell View Post
I've been advised that the MeanWell ones don't have a sense wire to monitor voltage drop in the cable. They'll work, for a while, but long term they are not advised from an engineering point of view.
None of the original ones do, either.

Highly expanded desktop Amigas are somewhat of an anomaly; most devices that need lots of current regulate it on the board itself (or have an internal power supply) in order to avoid voltage loss over long cables.
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Old 19 April 2019, 10:30   #12
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Quote:
Originally Posted by ItsTheSmell View Post
I've been advised that the MeanWell ones don't have a sense wire to monitor voltage drop in the cable. They'll work, for a while, but long term they are not advised from an engineering point of view.
As an engineer who regularly works with industrial PSU modules like this, I can tell you that that's rubbish.
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Old 19 April 2019, 11:24   #13
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It was Jens Schofield from individual computers who said it.
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Old 19 April 2019, 12:23   #14
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And while he's normally extremely competent on technical matters, there's no way the power cable can change properties enough over time to cause problems that aren't there from the start.
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Old 19 April 2019, 12:58   #15
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Originally Posted by ItsTheSmell View Post
It was Jens Schofield from individual computers who said it.
This is why started a topic a few weeks ago where I asked advice for my A1200 PSU.

When asked, Jens doesn’t recommend any of the newer PSU’s for the Amiga. I’m actually surprised why he doesn’t come up with one himself... shouldn’t be very hard for someone with his skills...

I ended buying one of the readily available ones, based on the Mean Well RT-50B. I guess time will tell if it was a good choice or not...
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Old 19 April 2019, 15:26   #16
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Did you have a failing indivision board and was i t the PSU that damaged it?
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Old 19 April 2019, 16:00   #17
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My original power supply was blamed for my Rapid Road not working properly in my A1200. Despite me trying multiple A1200's and multiple original PSUs.

Read into that what you will.

I have had it running perfectly when I removed the ACA1233. Again, take from that what you will.

I have a MeanWell open frame replacement PSU here but I have not got round to fitting it into my large A500 case yet because it does not physically fit. I need to butcher the inside of the case to do so and I haven't really wanted to do that.
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Old 19 April 2019, 16:06   #18
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One might ponder this: Many of the modern PSU modules with three outputs that fit the Amiga requirements, are also often approved for "Medical" use, ie. they are fit to be used in critical life-supporting equipment.

So they should be good enough to trust your life in them, but you think they might not be of enough quality to run your 30 years old home computer...

Just thinking out loud.
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Old 19 April 2019, 16:08   #19
ItsTheSmell
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Has anyone had a meanwell do any damage to any item. I'm questioning if this is Jens get out clause. The aca500+ has a 2 year warranty but he only fixes/replaces up to 6 months and after that you have to prove the fault was in the board from the factory.
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Old 19 April 2019, 18:25   #20
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Yeah, they're the standard EU regulations regarding warranties. Most companies will make it more difficult to get a warranty repair or replacement after 6 months, because in general, if something is faulty, it will fail in the first short while of use, and after that it will run until it wears out or suffers damage.

With appropriate equipment it would be pretty simple to show that the PSU isn't at fault. I can't imagine Jens would say that all the original PSUs are all in perfect working order either - most have ageing capacitors which can cause the stability and regulation to suffer, resulting in increased ripple, which in turn can stress components and can cause crashes under heavy loads. An oscilloscope trace recording over time will show whether a PSU is behaving itself or not; unfortunately most end users don't have that sort of thing lying around, so it's difficult to rule out such a large variable as the PSU.
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