Comments on: Commodore Amiga 500 full replacement Power Supply

By: illys

illys — Mon, 30 Oct 2023 20:55:05 +0000

@Mech
Yep! I am late here, but this may be of interest for future readers.
Thanks @xAD/nIGHTFALL for the article, and thanks @Mech for the technical insight.

My original A500 PSU (“Power supply A 500 P/NO 312503-03″) just failed and I am about to follow this mod.
@Mech, to answer your concerns:

1) About power: my original A500 PSU is +5V 2.5A, +12V 1A and -12V 0.1A. So this T-40B matches with some security margin (I have no other mods but a Gotek).
2) About cooling: I found the datasheet (Google: “Mean Well t-40b pdf”) and it states “cooling by free air convection”. So it should be fine… provided the vents on the Commodore box allow enough air flow.

About the cooling, feedback from the people who did the mod a few years ago would be nice.

By: solar inverter

solar inverter — Thu, 04 Oct 2018 17:23:29 +0000

its very nice and helpful blog about electronic thanks for sharing

By: mxa

mxa — Thu, 05 Jul 2018 14:51:45 +0000

Well, to answer my own question :p it appears this is indeed the case according to the datasheet for the RPT-75B – 0.2A minimum on the +12V line & 0.1A on -12V (& 0.6A on 5V)

So on paper, it does not seem to be much of a difference (although 0.6A on 5V might actually be a drawback)

In this regard the RT-65B is probably better, with min req of 0.5A on the 5V line, 0.2A on 12V (same for all) and 0A on -12V.

Sorry for the extra noise. But if anyone has encountered any practical differences/benefits it would be useful to know.

By: mxa

mxa — Thu, 05 Jul 2018 13:57:35 +0000

Anyone know if the RPT-75B also has the 0.2A minimum requirement on the +12V line?
(Yes, I still haven’t mounted my RT-50B yet – way too many projects in the air)

Contrary to other claims about being a drop-in replacement, the RT-50B also does not fit in the case via any mounting holes so either drilling or making a simple adapter plate is required. Its size was the main reason I got it (and the reduced hassle of having to modify the chassis, which turned out one still had to do!) :)

By: William Lorvik

William Lorvik — Fri, 27 Apr 2018 21:14:13 +0000

Mean Wells RT-50B is plenty powerful enough with its max 5A rating on 5V line. Keep in mind it requires minimum 0.2A load on +12V for stable operation, so a power resistor (39 Ohm, 5-10W) should hjelp. You can do the same for the -12V with 82 Ohm 3W if you want. My A500 psu was fine, so I just recapped it.

By: Eriond

Eriond — Mon, 23 Apr 2018 11:16:29 +0000

Just for info, I’d recommend the MeanWell RPT-75B because it has superior specs (6A on the 5V rail), and fits the case good enough. You will however have to make your own mounting plate to accommodate for the new hole pattern of the PSU. I will post such an adapter on GrabCAD for those who have a 3D printer nearby. So far I have converted 3 of mine PSUs, and they can power any hungry accelerator, disk or memory expansion without breaking a sweat… :-)
Link: https://www2.mouser.com/ProductDetail/MEAN-WELL/RPT-75B?qs=%2fha2pyFaduj89TKwmmRVV00hY%2fzVMNOqNSgmhXyUhX0%3d

By: mxa

mxa — Fri, 02 Feb 2018 17:28:47 +0000

Thanks for clarifying that @Dave. I guess I’ll just cut off (& terminate) that cable then. I was thinking of hooking it up to ground (based on suggestions from others), but not sure if there’s any real benefit in this.

btw-it’s funny how all the pics and the videos (that I’ve seen so far) omit this little information as that cable is quite prominent. :)

Cheers,

Martin

By: xAD / nIGHTFALL

xAD / nIGHTFALL — Thu, 01 Feb 2018 13:54:58 +0000

@mxa

Yep, it’s the “shield”

http://www.ianstedman.co.uk/Amiga/amiga_hacks/Amiga_Power_supplies/power-plug.JPG

You don’t need this butthe design of the original PSU is like this.

Dave.

By: mxa

mxa — Thu, 01 Feb 2018 09:17:12 +0000

Excellent job with the pictures. One question though, what did you do with the large black cable (in IMG_1402 & 1406?) I.e, the one which comes out together with the five connectors on the left/DC-side (and was soldered onto the other side on the original PSU)? I can’t see where it goes, and it’s not hooked up to any of the terminals on the new PSU, AFAIKT. (It disappears in the rightmost corner of pic IMG_1402 – http://www.nightfallcrew.com/wp-content/gallery/commodore-amiga-500-replacement-power-supply/thumbs/thumbs_IMG_1402.jpg

Thanks again for documenting this. Guessing a lot of Amiga owners are going to replace their ailing with a new Meanwell PSU.

By: xAD / nIGHTFALL

xAD / nIGHTFALL — Mon, 29 Jan 2018 15:21:35 +0000

@Solo761 Hi Solo, mhhh nope, here with the T-40B works perfectly , tried some years ago with A500 and A600 (without internal/external additional cards)

By: Solo761

Solo761 — Sun, 28 Jan 2018 21:57:53 +0000

A bit late to the party… I have RT-50B that I’m trying to use in a project with one loose A500 motherboard. It works and powers it up fine, but I have slight waves going across my monitor that I don’t have when using normal Amiga PSU, aka noise. Is it possible to get rid of it, or that’s just how it goes when using these kinds of PSUs?

By: William

William — Mon, 24 Apr 2017 10:49:46 +0000

Esiste qualche dettaglio in più di questo progetto?

By: xAD / nIGHTFALL

xAD / nIGHTFALL — Sat, 19 Nov 2016 09:20:06 +0000

@Mikrokernel

Ciao Mikro

Questo ALIM dato il basso amperaggio non va bene su 1200 carozzati , va benissimo su un 500/600/1200 liscio senza nulla, per la tua situzione ti consiglio di optare per modifiche con ATX, vedi post:

http://www.nightfallcrew.com/01/03/2015/my-amiga-1200-recapped-e127r-fix-atx-power-supply/

By: Mikrokernel

Mikrokernel — Mon, 14 Nov 2016 16:02:01 +0000

Ma saresti in grado di farne uno per un A1200 che monta PPC e Bvision?

By: xAD / nIGHTFALL

xAD / nIGHTFALL — Sat, 27 Feb 2016 09:55:45 +0000

@Mech This is just an example of how you can do, certainly i will not use this power supply 24h switched on.