Mean Well RD-50A (for a maxed out STe)

[Pacman]

I'm considering a Mean Well RD-50A power supply replacement for an STe, as I see they're often mentioned in Atari ST related forums/threads. From what I read they appear to be of good quality, are reliable and reasonably priced, in addition to having the required voltages of course.

My STe's Mitsumi SR-98 has the following specs
+5V @ 3A
+12V @ 0.2A

The Mean Well RD-50A has these specs:
+5V @ 6A
+12V @ 2A

So twice the rating for +5V and 10x the rating for +12V; should suffice nicely for a stock STe! :D

But mine's a little different as it has a lot of add-ons and will be recased. I know it's really a wild guess without measuring, but I'd still like to hear your opinion on whether it'll likely suffice or if I have to individually measure each add-on's power draw etc. Here's what the power supply must power:

• STe motherboard
• Sony MPF-920 HD/DD floppy disk drive
• Exxos HD module v7.0
• Ricoh based realtime clock
• MonSTer (dual IDE-interface, 8 MB ALT-RAM, Flash-ROM)
• Compact-Flash memory card (attached to the MonSTer via a CF-IDE adapter)
• Unicorn (ACSI-USB adapter) for removable USB-flash devices, SD-cards etc.
• Link '97 (ACSI to SCSI host adapter)
• Self-designed 2-way (multiplexer based) ACSI port selector switch board
• USB-hub attached to the Unicorn
• ImpoSTer (USB keyboard/mouse adapter
• USB-hub attached to the ImpoSTer
• USB-keyboard
• USB-mouse
• ST-ESSC (additional high-speed serial ports)
• Small internal speaker with amplifier PCB
• C-Lab/Emagic Unitor II (MIDI expander for cartridge port)
• C-Lab/Emagic Human Touch (MIDI synchronizer -attaches to Unitor II)
• C-Lab/Emagic LOG-3 (MIDI expander for cartridge port)
• C-Lab/Emagic Combiner (MIDI dongle-selector for cartridge port)
• Discovery cartridge
• Exxos diagnostic cartridge
• Self-designed 4-way (multiplexer based) cartridge port selector switch board
• 2 or 3 cartridge port buffer boards
• C-Lab/Emagic (MIDI expander for serial port)
• Self-designed 2-way (multiplexer based) serial port selector switch board
• Self-designed 3-mode (multiplexer based) VGA/Atari monitor output board

Phew! I think that's about it :lol:

[exxos]

All the "old skool" hardware, while power hungry, seemed to run fine on the original PSU. Most modern upgrades tend to use low-power chips and do not significantly add much current draw.

The RD-50A is a overkill really IMO. A stock ST generally only pulls about 2 amps anyway. Still gives 1amp headroom on a original PSU.

[rubber_jonnie]

I can't imagine you're running all of that all the time, I suspect the Meanwell will be more than up the job.

[stween]

Echoing the above, I imagine this won't worry the RD-50A.

One thing worth considering is that the RD-50A is a tight squeeze: it might fit on the existing PSU frame or you might need to cut to get it to fit, and either way it'll be snug. I've never used the other Meanwell options, but there are smaller Meanwell PSUs that I'd consider next time. (I don't know the specs or model numbers off-hand.)

Relatedly, I'd also consider going down this route: https://exxosforum.co.uk/atari/last/psu_2025/

[Pacman]

Echoing the above, I imagine this won't worry the RD-50A.

Thanks for confirming!
Is the RD-50A a good and reliable PSU? Or are there others to consider?

One thing worth considering is that the RD-50A is a tight squeeze: it might fit on the existing PSU frame or you might need to cut to get it to fit, and either way it'll be snug. I've never used the other Meanwell options, but there are smaller Meanwell PSUs that I'd consider next time. (I don't know the specs or model numbers off-hand.)

The Mean Well RD-35 is a little less wide (99x82x36mm) with +5V @4A and +12V @1A
(compared to the RD-50 sized 99x97x36mm).

Relatedly, I'd also consider going down this route: https://exxosforum.co.uk/atari/last/psu_2025/

Wow! Very interesting. Hadn't seen that one. How do those modules differ from a "normal" switched mode power supply?
Will that PCB be available from the Exxos store at some stage?

Fortunately I'm not restricted by those space limitations you mention as the entire STe with its add-ons will be housed in a 19" rack enclosure. All I need is a reliable PSU with enough power, and a PSU with an enclosure is also nice, so I don't have to mess around with modifying ST power supply frames.
And I'm also aiming for a quiet computer .....something I always wished for back in the 90's/00's when I used the STe actively for making music, with a jet-engine sounding SCSI hard drive whizzing in the background. Those were the days :lol:
It might be an idea to put in a (silent running) modern fan (Noctua?) with a temperature control board which turns it on only when needed, first at a low speed. Or is this likely unnecessry with some good vent openings?
And will it make a difference to get a PSU without an enclosure, for even better ventilation? Not as safe as (the enclosed) RD-50A when setting things up and testing, but perhaps worth it when I'm all done and have the 19" rack in place.
I see that Mean Well have "open frame" power supplies too. Something like the open frame Mean Well PD-65A with +5V @ 5.5A, +12V @ 2.8A. Or even the lower powered open frame Mean Well PD-45A with +5V @3.2A, +12V @2A.

All the "old skool" hardware, while power hungry, seemed to run fine on the original PSU. Most modern upgrades tend to use low-power chips and do not significantly add much current draw.

Interesting. And I won't even run all the hardware at once (i.e. the cartridge devices will be grouped as they don't all work together, using a switching circuit).
Yes, I suppose even though I'm not going for all-SMD designs myself they shouldn't draw too much power.

The RD-50A is a overkill really IMO. A stock ST generally only pulls about 2 amps anyway. Still gives 1amp headroom on a original PSU.

OK, noted.

Here's a diagram of what I listed in my previous posting, and what I'm working on with my STe:

19_rack Atari STe_24_layout.png

[Pacman]

I can't imagine you're running all of that all the time, I suspect the Meanwell will be more than up the job.

That's true.
For the cartridge, modem port and ACSI ports there will be a switch for each so it's "one or the other" instead of "everything at once" solution.

[rubber_jonnie]

I can't imagine you're running all of that all the time, I suspect the Meanwell will be more than up the job.

That's true.
For the cartridge, modem port and ACSI ports there will be a switch for each so it's "one or the other" instead of "everything at once" solution.

Don't over think it :)

[mikro]

Let me just say that you have got quite an impressive setup there!

[Pacman]

Don't over think it :)

True :lol:
I'm trying to keep it simple and functional.

Let me just say that you have got quite an impressive setup there!

Thank you. Many ideas throughout the years, but I've ditched a lot of them (CD-ROM/CD-writer etc.), so now I'm left with mostly add-ons I actually need and will be using.
Most of the add-ons are already acquired, but there are several projects I'm working on designing myself/will be designing in order to get it all done (switching circuitry for the various ports, VGA/Atari video output board, front-panel cartridge extension board for the C-Lab Combiner etc.).