Ian Stedman's ATX Power Adaptor

[Totomoto]

This one is now available on GitHub and I would like to build one in order to upgrade my A3000 PSU.

I am not a hardware expert but I checked PCB design and it seems unfinished to me. For instance, there are some unconnected +5V rails which is a little bit odd. Can someone more experienced take a look at this before I order PCB?

Also, it would be nice if we could make some updates on the project, like make it compatible with 24 pin ATX power supplies. I would do it myself but I have no experience with EagleCAD.

[jbenam]

Your best bet is probably to PM Ian himself and link him to this thread, since he is a quite active user of this forum

http://eab.abime.net/member.php?u=10761

[Daedalus]

Having a quick look at the schematic there (the multipurpose bigbox one), it seems it's all in order. All the +5V rails are tied together. The -5V rail isn't tied to anything, and that's deliberate. Most PSUs lack a -5V rail so it's generated separately from the -12V rail instead.

What you're missing on the image of the PCB is the copper pour areas, which aren't filled in. These only have their outlines visible, but the odd, seemingly unconnected 5V lines are simply connecting the pads to that filled area. Within EagleCAD these areas can be filled in and it would be easier to see how it's all connected then.

ATX-24 is backwards compatible with ATX-20. Once there's physical space for the extra 4 pins of the 24-pin connector, it will connect and work correctly. Your Amiga is *extremely* unlikely to need the extra power available on the additional 4 pins.

[Totomoto]

Thank you very much. I know ATX-24 is compatible with ATX-20 but you cannot simply detach 4 pins from the connector. I remember that older ATX supplies had that option.

[torsti76]

Just to confirm what @Daedalus wrote: I'm using Ian's adapter with my AA3000+ and my A3000, and it works beautifully.

Nonetheless, I recommend not to use a standard off-the-shelf cheap ATX supply with it, because many of those don't deliver a well regulated +5V supply. Also, don't aim at high wattages. The PSU then probably needs a relatively high base load to work reliably. If you want a recommendation, my best experience so far is with a be quiet! BQT SFX-300W.

[torsti76]

Originally Posted by Totomoto

Thank you very much. I know ATX-24 is compatible with ATX-20 but you cannot simply detach 4 pins from the connector. I remember that older ATX supplies had that option.

You don't need to detach them. Just let them overhang, it will work both physically and electrically.

[Stedy]

Hi,

I got your message. The Github archive include the Gerber images I used to get the PCBs fabricated, look for Multipurpose-ATX-gerbers.zip (Original/Big box) and Small-form-factor-ATX-gerbers.zip (picoPSU variant). If you click the Ratsnest icon in EagleCAD, you'll see all the copper pours filled in.

I don't use the 24 pin ATX connector as it is more expensive and needs a bigger board. That connector is the most expensive item in the bill of materials! I left clearance if using a 24 pin ATX power supply.
The un-used 3.3V supply pins are connected together as some ATX supplies have remote sensing on this output and if missing can cause load regulation issues on +5V.

Good news, these adaptors will be available again shortly from an Amiga retailer. I shipped the first batch today, I'll let them announce further details and pricing.

[GearCross]

I was looking into building one of these adaptors myself, to use with my A1200, but the fact that I'd need to get a programmer for the PIC just for this, would make it a fair bit costly and I'd probably not use it ever again, so I quickly put that idea aside.

I guess I'll wait until they're available at the retailer. Can you tell us the retailer or retailers it's going to be on, so that we can keep an eye on for news on their websites/social media platforms? Thanks.

[attle]

Originally Posted by torsti76

Just to confirm what @Daedalus wrote: I'm using Ian's adapter with my AA3000+ and my A3000, and it works beautifully.

Nonetheless, I recommend not to use a standard off-the-shelf cheap ATX supply with it, because many of those don't deliver a well regulated +5V supply. Also, don't aim at high wattages. The PSU then probably needs a relatively high base load to work reliably. If you want a recommendation, my best experience so far is with a be quiet! BQT SFX-300W.

How well (or not) does it fit in the A3000D?

[torsti76]

Originally Posted by attle

How well (or not) does it fit in the A3000D?

Unfortunately, it's about 5 mm too high. But I use only this supply during buildups, repairs and testing, because it proved most reliable.

A good industrial grade Flex-ATX supply, rated for 250-300 W is a good fit for the 3000. Fortron makes very nice ones that work great (but are expensive)

[bitter]

Originally Posted by torsti76

Unfortunately, it's about 5 mm too high. But I use only this supply during buildups, repairs and testing, because it proved most reliable.

A good industrial grade Flex-ATX supply, rated for 250-300 W is a good fit for the 3000. Fortron makes very nice ones that work great (but are expensive)

That's the thing, there has to be a supply out there and fits well and supplies enough stable 5V current, has nominal drop, and has low ripple. I finally got my 3000, and am willing to spend the money on a nice PSU, alas I can't find anything.

I'm not comfortable tinkering with it myself, and it sucks that while there are so many options for the flat Amigas, there is nothing being offered for the desktops...

[torsti76]

Originally Posted by bitter

That's the thing, there has to be a supply out there and fits well and supplies enough stable 5V current, has nominal drop, and has low ripple. I finally got my 3000, and am willing to spend the money on a nice PSU, alas I can't find anything.



I'm not comfortable tinkering with it myself, and it sucks that while there are so many options for the flat Amigas, there is nothing being offered for the desktops...

I am basically in the same situation as you are.

I've got my A3000 a while ago, and I can see through the cage of the PSU that the previous owner put some replacement in there. If it were original, I'd probably change the caps and use it, but since it's been tinkered with already, and I don't know the exact specs, I don't trust it.

I tried to find an open cage supply that fits the original PSU case, but options seem very limited here. All I found are small form factor PSUs with wattages around 60 or so - much too low.

So, in the end, it will most probably be some 3D printing, @Stedy 's adapter, and a Fortron or Seasonic Flex-ATX supply...

IMHO, "real" replacements for the big box PSUs will never be available because of liability issues and certification costs. (Aside from odd form factor housings, low ripple demands and so on)

[Stedy]

Originally Posted by GearCross

I was looking into building one of these adaptors myself, to use with my A1200, but the fact that I'd need to get a programmer for the PIC just for this, would make it a fair bit costly and I'd probably not use it ever again, so I quickly put that idea aside.

I guess I'll wait until they're available at the retailer. Can you tell us the retailer or retailers it's going to be on, so that we can keep an eye on for news on their websites/social media platforms? Thanks.

Hi,

Retropassion will be stocking these adaptors. They should be on the website in a week.

I used the PIC Microcontroller and Tag-Connect adaptor as they are cheap and small to use and give an accurate 50Hz/60Hz tick. A cheap PICKIT clone can be used by anyone wanting to build their own board.

[RetroPassionUK]

Hello!

We have now listed the items:

CDTV PSU Adaptor - https://www.retropassion.co.uk/produ...v-psu-adaptor/

Amiga PicoPSU Adaptor for A500,A600, A1200 - https://www.retropassion.co.uk/produ...copsu-adaptor/

Amiga ATX PSU Adaptor for A1000, A2000 & A3000 - https://www.retropassion.co.uk/produ...x-psu-adaptor/

Thanks!

[alexh]

Thanks. The CDTV one might prove useful.

[Daedalus]

The slightly fancier version of the cheap TL866 ROM burner that many people use (the TL-866A) has an ICSP port that can also be used for programming PIC chips.

Maybe an option for a future revision: with an additional input pin (e.g. PIC12F629), it would be possible to include a software shutdown feature using a feed from one of the CIAs. I built a few ATX adaptors like this a while back and they worked very well, but never got around to bringing it further than a small test batch.