Solo761 wrote on 2022-03-27, 14:03:
Better in terms of reliability or power efficiency? I'd expect modern ones are more reliable, but 486 isn't actually power hungr […]
Kahenraz wrote on 2022-03-26, 22:45:
Even if the PSU could be refurbished, this is one component that has simply gotten better with time and there is little reason to use an original without a specific requirement, such as a -12V rail.
Better in terms of reliability or power efficiency? I'd expect modern ones are more reliable, but 486 isn't actually power hungry and decent modern supplies are 450+ W so who knows how they perform in regards to these kind of usages.
I wouldn't trust this PSU mostly because capacitors are almost 30 years old. But if I replace them with new ones and that would "restore" it to at least "as when it was new" state (plus new cooling fan) it should be good enough for this PC. That's why I asked what the consensus is on PSU cap replacement 😀.
Unknown_K wrote on 2022-03-26, 23:06:
Hard to find new supplies with a decent 5v section.
It's a bit questionable how many amps this one has. There are no specs written anywhere except 200W mark 😁.
And it being from cca 1994 it was probably meant for 486 CPUs which aren't 5V demanding as Socket A CPUs are. So I don't think it's actually something exceptional in this department.
The later "ATX 12V" standard was established because power consumption became excessive for the usual 5V rail, meaning too many amps or to much loss at a given cross section of cable or PCB conduct.
For the same reason the power grid uses voltages beyond 100 kV for larger distances. Losses scale with current while power ('P', Wattage) scales with current x voltage.
So, since a long time, logic semiconductors had used 5V, period - but some 486DX2 dropped to 3.3 and it eventually became more practical to use 12V right up to the CPU or GPU and then transform it to high current, low voltage there.
Average 200W AT PSUs should have around 100W or 20A for +5V alone. E.g. I bought this beast as a spare and NOS for a Euro:
Only 8A for 12V, that's 96W.
That thing is probably ancient - full size AT PSUs mostly died out around 1990, I'd say. What we're used to today was called a "slim" AT PSU.
AFAIK, back then, 12V was mainly for stuff that by IT standards, needed "real" physical power, i.e. sound card amps, fans, drive motors.
So, have a look at high-end 1980s motherboards and full size ISA cards of the time - if you needed a lot of RAM, it really became heavy industry. And most PSU fans were loud AF not only for the PSU's losses but because it was supposed to be the only ventilation.
But for the basic, non-3D-accelerated x86 system of the 90s, any 200 W PSU should do, including any normal ATX one with adapter and many of these:
ATX to AT pico Adapter! + Fan Headers, -5v, and 3.3v (Released)
There are official numbers to find for 486 and 586 CPUs - I'd say most were around 10 Watts.
Was there progress?
Reliability/risk of hardware damage: I think the issue is overrated. Some old PC systems have sentimental value but how often does it really happen that the PSU itself will take one down? (And not an external power surge)
The only PSU that did that to me was acutally a fancy, high end, not that old Enermax dual fan ATX device which took out a Socket A board and GF4. CPU was fine.
One AT PSU recently went up in smoke when I dry-tested it for the first time. Capacitor exploded.
So, it may happen, but will the risk be significantly lower with a more recent PSU, even a new and expensive one?
Going by risk, you'd as well have to complety seperate it from any grid or network after use or a nearby lightning strike will take it out. Also, EMP bombs. 😜
Efficiency: Probably quite a bit, but it won't justify buying a new "80+ noble metal" PSU and adapter - neither for environment nor wallet. Their ratings are for certain load ranges around 50% and how often will you reach those with a 486?
(In general, if it's about power usage, get a Raspberry Pi with emulator 😉)
The AT PSU In your picture there: The fuse is soldered on, they did not bother to install a socket. So, based on that, it probably was a cheap one. But if it works?