exxos's Atari, Amiga & retro forum

Hi, I’m hoping someone can advise before I undo all the work I’ve done installing this.

I’ve fitted the 2025 Exxos replacement PSU to my Atari 520STE, along with the recommended replacement power switch. The PSU bolts perfectly onto the original metal base using the existing mounting holes, and I’ve completed the wiring and continuity checks successfully.

Unfortunately I’ve hit a physical clearance problem.

The original PSU shielding plate is extremely difficult to fit over the new PSU. I managed to get it on by carefully routing and cable-tying the wiring out of the way, but even then the Atari’s plastic top case no longer sits naturally. It noticeably rests on/pushes against something underneath and would have to be pressed down while tightening the case screws, which I really don’t want to do.

I’ve also tried it without the PSU top shield, but with the rear shielding arrangement in my particular STE there still seems to be too much obstruction for the plastic case to fit as it originally did.

Is this expected with the 2025 PSU in some 520STE chassis/shielding revisions, or am I missing a particular way this is supposed to be mounted or routed?

I really don’t want to force the case closed or modify the original Atari if that isn’t intended.

Thanks very much for any advice.

Looking at your last image it looks like the rear IO shield isn't fitted properly.

exxos wrote: 10 Oct 2026 17:59 Looking at your last image it looks like the rear IO shield isn't fitted properly.

Sorry, I should have labelled the photos clearly.

This is how the plastic top case fits on top when I have the PSU shielding plate fitted. It almost fits but not quite. See below:
And this next photo shows that if I remove the PSU shielding plate and try fitting the plastic top case, then not only am I still battling with the PSU height and getting the wires to lie out of the way but the rear IO shield tab then creates a new obstruction because there is no PSU shielding plate for it to screw into, which would bring it away from the casing and out of the way. See below:
I'm considering trying to remove that rear IO shielding tab. However I'm not entirely sure how it comes off, but I'm pretty sure I'll have to remove and disconnect the main PCB entirely again to do it, and even then I'm not confident it would give me the clearance that it needs, so I'm not in a rush to do that right now.

you need to fit the 3 black screws that hold the IO shield to the rear of the PSU metal top, If you don't the IO metal sticks out and stops the plastic lid fitting on

From your other pic the PSU metal top looks like it fits on ok so i see no other reason why the plastic lid wouldn't fit

To prove it get a cocktail stick or similar and push the metal plate back and see if the plastic lids fits then

atarifreakz wrote: 10 Oct 2026 20:45 To prove it get a cocktail stick or similar and push the metal plate back and see if the plastic lids fits then

Ah, thanks for the tip about the cocktail sticks! I just got my wife to help provide an extra hand by keeping that IO shield tab out of the way by using two cocktail sticks while I guided the plastic top cover on while making sure all the PSU wires stay as low as possible.

Unfortunately, as I suspected, there still isn't enough clearance even with the main PSU shielding plate removed and making sure that IO shielding tab is out of the way. The new PSU still seems to be obstructing the top cover. To make it fit like this I'd need to compress the wires on top and bend the plastic top cover over them whilst screwing in the from the bottom. Which I don't really want to do, it seems to almost fit, but sadly doesn't.

Maybe this will give you some clues
https://www.exxosforum.co.uk/atari/last/stedis/main.htm