The LC-Power LC6550GP2 550W is wildly oversized for a venerable SS7 system that will never draw even 100 real watts. It's a barely passable PSU on the fringe of being dangerous, for it doesn't hold voltages within ATX specs above 80% load. Ripple is within limits, so at low loads powering an ancient comp should be relatively safer. But I wouldn't plug any modern more powerful system into that thing.

The LC-Power LC-420H-12 420W is again wildly oversized for a 486 system:

25A on +3.3V, 25A on +5V & 15A on +12V. You can power several 486 systems with that PSU.

I know that these LC Power PSU's aren't very good, but should be OK for legacy systems.

My LC-Power LC-420H-12 420W does not have those specs! Is that version 1.3?

Because this is what i'm using:

http://www.lc-power.de/fileadmin/user_upload/ … 3_datasheet.pdf

The specs in that pdf don't make sense:

3.3V x 16A ===> 53W
5V x 16A ====> 80W
12V x 15A ==> 180W
_________________
TOTAL =====> 313W (not 420W)

Anyway way overkill for a 486 system.

It might be overkill, but it's not like we can just go to a computer shop and buy a perfect ATX PSU for legacy systems. I have not seen PSU's with less than 400W for a while now. And surely it's not easy to find -5V capable ATX PSU's. Without going eBay at least.

What matters most is to find if these cheaper PSU'd are safe enough to use with old systems. From my experience using them, it seems so.

What I mean with overkill is that you don't need to worry at all about 400+W PSUs not being able to power 50~100W ancient systems 😀 .

Some examples of current low-power PSUs,

Very good: Seasonic G-360, Seasonic SSP-350GT

Decent: Antec Basiq BP350, Cooler Master Elite Power 350, SeaSonic SS-300ES

The -5V is problematic today, you'll find either crap or rip-offs. I'd better get some old decent PSU and recap it for good.

Isn't here a guide for building a simple -5v source?

Modern AT 300W PSU with -5v - expect that to be noisy however, it's meant for server usage.

Sooner or later people will start refurbing old AT supplies instead of tossing them and just using whatever is cheap.

On ebay you can still find older NIB ATX cases with older style 250W supplies that you will replace with something better, so keep them handy.

bristlehog wrote:

Modern AT 300W PSU with -5v - expect that to be noisy however, it's meant for server usage.

I highly doubt noise was a concern back in 1990-97. Your average power supply from that period was far from clean output. If the concern is dirty power causing problems with sound cards, almost all cards had some filtering on the input power rails since power supplies varied widely. RF emissions were enough to pass FCC Class A in most cases. I remember my first 486's Enlight power supply causing interference on a TV in the next room!

NJRoadfan wrote:

RF emissions were enough to pass FCC Class A in most cases. I remember my first 486's Enlight power supply causing interference on a TV in the next room!

HAHA! I remember we couldn't listen to the radio that was 10 feet away from our 486 because all the signals went out. 🤣

I've used these in two of my recent restorations/builds. They both seem to work great:

Rosewill RP600V2-S-SL 600W

Rosewill RV350 350W

Last year, I also replaced the ancient AT PSU in my Pentium 200MMX system with one of these:

StarTech.com 230 Watt

It also seems to work very well. It certainly can't be any worse than the no-name brand PSU that was in there previously.

I meant the audible noise from PSU fan. For my 400W EPS Emacs PSU it's a nasty hi-freq buzz.

There's no doubt that a silent PSU is desirable. One of the things that i appreciate about my vintage systems is the silence. One can argument that noise is part of the retro experience, and while i do agree, i will never go back to a noisy system. I started to enjoy even more the sounds that come from my speakers and became pretty much an audiophile. Noise is not desirable.

I guess that even lower quality PSU's could be recapped with higher quality capacitors. I think that these PSU's won't have big trouble powering our vintage systems.

What we should do is to compile the model names of ATX PSU's available on the market that still supply -5V and are suitable for our vintage needs.

bristlehog wrote:

Modern AT 300W PSU with -5v - expect that to be noisy however, it's meant for server usage.

That's a total rip-off, a hundred bucks and wires ain't even sleeved 🤣 . Found a pic of the ATX version guts here: Russian / Googlenglish.

Nothing special and weak +3.3V rail regulation. The Seasonic G-360 is miles better and $30 cheaper.

KT7AGuy wrote:

Rosewill RP600V2-S-SL 600W

600W for retrocomps? You really like killing mosquitoes with cannons 🤣 .

I just gutted a dumpster PC for a black LCD Power LC6550H. Works fine, no bulging caps and even provides 0.5A at -5V. Not so the other PSU I found which is a Xilence 350W XP350. Only 0.3A at -5V.

If you require -5V and your PSU does not provide it, you can easily make your own -5V rail from the -12V rail, using a 7905 IC and two capacitors.

quick example circuit from Google:

edit: bad example, the caps are wired the wrong way around 🤣

TELVM wrote:

bristlehog wrote:

Modern AT 300W PSU with -5v - expect that to be noisy however, it's meant for server usage.

That's a total rip-off, a hundred bucks and wires ain't even sleeved 🤣 . Found a pic of the ATX version guts here: Russian / Googlenglish.

Wires aren't sleeved because this is a PSU meant for servers. Emacs produced a line for gamers, all black PSUs with sleeved cables, 120mm fans and still with -5v rails, but they all seem to be discontinued.

Beware of 'Googlenlish'! In Russian there's:

PowerCheck test found no serious flaws as well

Googlenglish:

Test PowerCheck also found serious flaws

bristlehog wrote:

Beware of 'Googlenlish'! In Russian there's: […]
Show full quote

Beware of 'Googlenlish'! In Russian there's:

PowerCheck test found no serious flaws as well

Googlenglish:

Test PowerCheck also found serious flaws

I just submitted a translation suggested fix, we'll see how long it takes to be applied - if ever 😉

🤣 🤣 🤣

Still looks a rip-off to me.

Behold my restored super-Deer (with -5V rail inside! 😎 ):

Pannys and Rubys all around, and plenty of cooling to make them last.