What's the weakest PSU that can power this?

[Leo V]

I will likely order a fan-less PSU from TKpower.com for my mini-server. What's the weakest power supply (45watts, 60w, etc) that can safely power the following:

* P3/600EB (15.8watts max)
* Maxtor DM80 5400RPM (~5watts)
* 3com nic (negligible power)
* Intel i810E legacy-free motherboard with onboard LAN, i810 video and sound
* One single-sided DIMM stick

It's a server so I need a safety margin, but I don't want anything extravagant either.

 

[Mark R]

I've seen similar specified machines from a major OEM come with a 100 W PSU. Most PSU manufacturer's give reliability and life time ratings for a 70% load, so I'd keep the 30% safety factor.

Remember that hard drives take a significant surge for a few seconds during spin-up - Allow 10 W for switch on. Allow 5 W for a DIMM, about 10 W for the mobo and 80 % efficiency for the CPU voltage regulator.

Additionally, don't forget that you must de-rate the PSU specification for temperature - air temperature above room temperature means decreased power output.

In my opinion a 60 W is the absolute minimum acceptable - such a PSU should operate at just over 70% load. The vast majority of this load will be on the 3.3 and 5 V supplies (this should be reflected in the PSU specifications).

 

[sharkeeper]

Take a standard 300W PS and remove the power transistors from the little internal heatsink. Bond them to a large heatsink from an audio amplifier by extending the wires as needed.

Cheers!

 

[Leo V]

Hehe, thanks. I'll get either a 65Watt supply or something stronger. sharkeeper, this PSU uses a FlexATX form factor, I'm afraid I can't perform this mod (and afraid to mess with a server's PSU! 🙂)

 

[Mark R]

Definitely don't extend the wires to the PSU's power transistors! Those transistors may switch up to 400 V (yes, even when powered from a 110 V AC supply).

Additionally, the high frequency switching performance of those transistors is likely to be greatly impaired by lengthening the wires - this may be enough to prevent the PSU working, or even cause catastrophic failure of the supply.

 

[Viperoni]

I also think a 60watter would be okay.
Would run warm, but it would run 🙂

 

[Leo V]

Hold it a second...

...you mean, a higher-rated power supply will actually run cooler on the same system? That makes a huge difference to me!

 

[jeremy806]

Just buy a 300W supply and be done with it. You can always use the PS elsewhere later then.
jeremy806

 

[madthumbs]

If its a server you may prefer quality to power rating. If you want stability go with a good brand first, power rating second.

 

[sharkeeper]

<< Definitely don't extend the wires to the PSU's power transistors! Those transistors may switch up to 400 V (yes, even when powered from a 110 V AC supply). >>



This is probably good advice for safety reasons.

As for timing issues with switching PS, it never was a problem when I did it. Of course, there was never more than 12 cm of distance! If you ran the wire across the room I think your power supply (and possibly YOU!) could be in for the new look! 😀

Cheers!