VOGONS


First post, by waterbeesje

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As most of us, we all come to a point where the good old PSU fails. Finding a suitable and reliable replacement can be hard if you require a massive 25+ volts current on the 5v rail.

You would end up buying a PSU that's got a massive overload on the 12v rail, probably over 600W total capacity and possibly over 1000W.

My thought:
Buying a regular 300-400W PSU (better brand) and add a simple but heavy 12v to 5v converter circuit, capable of transforming 12v 15A to 5V 35A.
Since all ground wires all are connected I don't think there would be any problem.

Would that add any unforeseen circumstances or even sparks?

Stuck at 10MHz...

Reply 1 of 9, by kolderman

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You build it, I'll buy it.

Reply 2 of 9, by The Serpent Rider

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if you require a massive 25+ volts current on the 5v rail.

Realistically speaking, no such thing is required in most cases. 30-35A is more than overkill for any 5V oriented system, outside of really extreme overclocking of some super crazy setup with massive amount of storage devices.

I must be some kind of standard: the anonymous gangbanger of the 21st century.

Reply 3 of 9, by luckybob

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I actually have done this for my OLD NAS box.

I took the PCI-e power. the +12v went to 6x 5v buck regulators. Each regulator provided 5v to 2 hard drives.So each pci-e 6-pin connector powered 12 hard drives. I had two of these cables and it worked perfectly for years, until I got a proper rackmount chassis. Just search ebay for something like: " DC-DC 3A Buck "

Modern power supplies work EXACTLY the same anyway. That's how they get the 90%+ efficency.

It is a mistake to think you can solve any major problems just with potatoes.

Reply 4 of 9, by waterbeesje

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The Serpent Rider wrote on 2020-09-26, 23:42:

if you require a massive 25+ volts current on the 5v rail.

Realistically speaking, no such thing is required in most cases. 30-35A is more than overkill for any 5V oriented system, outside of really extreme overclocking of some super crazy setup with massive amount of storage devices.

I was thinking of the most demanding platform for 5v: socket A.
Athlon: 70W = 14A
Graphics: 25 W = 5A
4 PCI cards, 1A each = 4A
4 drives, 1A each = 4A
Motherboard = 3A

Total 30A. Probably not too far off.

Yes I know these are extreme values, probably not occuring all at once, but a little overhead feels safe.

Stuck at 10MHz...

Reply 7 of 9, by dionb

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waterbeesje wrote on 2020-09-27, 00:04:
I was thinking of the most demanding platform for 5v: socket A. Athlon: 70W = 14A Graphics: 25 W = 5A 4 PCI cards, 1A each = 4A […]
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The Serpent Rider wrote on 2020-09-26, 23:42:

if you require a massive 25+ volts current on the 5v rail.

Realistically speaking, no such thing is required in most cases. 30-35A is more than overkill for any 5V oriented system, outside of really extreme overclocking of some super crazy setup with massive amount of storage devices.

I was thinking of the most demanding platform for 5v: socket A.
Athlon: 70W = 14A
Graphics: 25 W = 5A
4 PCI cards, 1A each = 4A
4 drives, 1A each = 4A
Motherboard = 3A

Total 30A. Probably not too far off.

Yes I know these are extreme values, probably not occuring all at once, but a little overhead feels safe.

The most demanding is dual SoA, at least the early boards without ATX12V connector (which made life a lot easier), I'd say they could top out over 35A.

However I don't think you need to take drives into account - if I understand your proposal correctly, it would run off the ATX(12V) connector, which means that 5V for Molex would come from the PSU's own 5V line; this one only needs to feed motherboard, CPU(s) and cards.

Reply 8 of 9, by waterbeesje

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@dionb; Drives will get the Molex indeed. So basically around 20-25A will be plenty enough. Dual soA is is not planned :p

@red-ray: The converter n your link might do the trick 😀 it provides 10-30A it says, so two of them might be ok. Still steep on the price... But I'll keep looking for this stuff.

Stuck at 10MHz...

Reply 9 of 9, by red-ray

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waterbeesje wrote on 2020-09-28, 14:26:

@red-ray: The converter n your link might do the trick 😀

After posting I am now wondering how good the regulation is, you need to check this. I suspect a single 10A one would be more than enough for the disks with the MB using +5 directly from the PSU.

Further I just checked what my Athlon system uses which is way less than 30 A.

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