Custom power-supply mounting in a server case

fake-name

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Feb 28, 2017
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A while ago I picked up a couple SuperMicro SC833 chassis for a really good price, which I'm using as general-purpose chassis for assorted projects.

While this is a relatively fine chassis, the power supplies it came with are kind of terrible. They're a three-unit redundant module, which isn't 80-plus certified at all. It's also rated for 760W, which is grossly overrated for what I have in it (I'm running a S2600CP mobo with dual E5-2660 V1 CPUs, and basically nothing else). This tops out at ~250W when it's completely loaded.

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Old power supply. It's HUGE.

Anyways, the idea here is to replace the existing power supply with something that's actually efficent.

Right now, you can buy an 80-plus gold Supermicro PWS-351-1H power supply on ebay for $20 a pop (I bought 2 for $40). It's similar in noise-level, and should be a damn sight more efficient.

Sure, I know supermicro makes a more efficent PSU for this chassis, but they're quite expensive, and I'd still be running it at ~33% of it's capacity basically all the time, so I'd be well down the efficiency curve too.

Here's the replacement power supply where it's going to live:
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It's amusingly disproportionate.

So, we need to mount to the screw holes where the old power supply went, and attach the new one. Some time in solidworks, and we have:

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A fancy aluminium mounting plate that accounts for all the odd sheet-metal features, and should fit the power supply (and a support bar, since it's basically dangling in free space).

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And with all the CAM work done. The oddball corners in the power supply recess are because I'm going to machine this with a 0.125" end-mill, and that means my minimum internal radius I can produce is 0.125" / 2. You push the corners out more so the part (which is basically rectangular) doesn't make contact on the corners.

Next up, making chips. I'm gonna go get food, and then fire up the bridgeport.
 

fake-name

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Feb 28, 2017
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Ok, let's make this thing

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I'm very much a redneck machinist, but I get by.

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First one looks fine, need to test the fit.

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Power supply fits

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And it fits the case nice. You might have noticed that the holes aren't fully drilled yet. I generally just spot-drill holes on the CNC, as I don't have enough tool-holders to keep both a centre drill and the actual through-drill in, and I'm too lazy to keep having to re-touch-off after swapping the drill in a drill chuck. I just leave a small centre drill in the chuck, with it's length set up in the tool table, and then do any final drilling by hand, on a drill press.

I've also broken some drill bits, albeit when doing very, VERY deep drilling under CNC control.

Time to pop out the second
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Both adapter plates done, with all the holes drilled out to size.

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Installed into the case. It's tight, but it does fit.

I have a bad habit of not allowing any slop in the design, which then interacts poorly with things like sheet metal, which are not tightly controlled in dimensions.

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Everything installed, except for the (optional) support bracket. Frankly, the mounting is rigid enough I think it's fine. I might dismount the supply if I were to ship it, but for just sitting around the house, it's more then enough.
 

nthu9280

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Feb 3, 2016
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Nice work! Man I went to school for manufacturing/Industrial engineering back in the day. Haven't touched a CNC machine since 1995.

One question, have you tried to mount the 1U 350w in the 3x housing and remove the pdb? Granted you will have 2 slots unused that need a cover.

Another point to keep in mind while S2600CP2j that I have settles down to under 180w idle with all my stuff, when I ran it prime95 it went over 300w IIRC. Also during boot & BIOS time it gets close to 300w per IPMI. That doesn't leave much head room for the power supply.
 

fake-name

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Feb 28, 2017
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One question, have you tried to mount the 1U 350w in the 3x housing and remove the pdb? Granted you will have 2 slots unused that need a cover.
The 1U PSU is much shorter then the 3X housing. The mobo cables are short enough that it'd have issues reaching when mounted like that.

Another point to keep in mind while S2600CP2j that I have settles down to under 180w idle with all my stuff, when I ran it prime95 it went over 300w IIRC. Also during boot & BIOS time it gets close to 300w per IPMI. That doesn't leave much head room for the power supply.
My logging shows a nominal power consumption of ~280W. That puts me right at about 80% load.

Power 1.png

Anyways, this is all hobby stuff, so if it winds up being a problem, it's not a huge deal. Worst case I'll have to upgrade to a PWS-441P-1H or a PWS-505P-1H.

Or I could redesign the mounting plate, and switch to a PWS-563-1H. They're $20 too! Or a PWS-605P-1H (80-Plus Platinum) is $50.
 
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fake-name

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So @nthu9280 made me slightly uncomfortable, and it wasn't that expensive, so I figured what the hell and bought a used PWS-605P-1H .

Mounting this was a little more complicated, because it doesn't have end-mounted screws. I designed a mount using some 1/4" * 2" flat bar stock:

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This was the furthest down I've had the knee on my mill. I couldn't use a drill press here, because my terrible benchtop drill-press doesn't have enough vertical clearance.

You can see my knee "power feed" (the drill motor on the knee crank). It certainly makes life easier.

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Here's the power supply mounted. I managed to screw up the machining in two places. I countersunk the holes a little bit too deep, and broke a tap in the last 4-40 hole (which is why one screw is missing).

I almost made a replacement, but at the point when I broke the tap I was so low on ****s that I honestly had no more to give. The whole mount is overengineered anyways, and I put the side-support with the missing screw on the bottom, where it's not under tension anyways.
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Here's the power supply installed, with my terribly messy wiring, and some layout blue still left on the aluminum.

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And the back-plate of the server. I fixed the over-countersunk holes with some thin stainless washers. They deformed, and took up the gap.

I got fancy, and made the fan hole match the octagonal cutout on the power supply.

And the reason I did all this:

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It looks like it resulted in an overall power saving of ~20-40 watts. Sure, it doesn't sound impressive, but considering the system this is for runs 24/7, every little bit helps.

You can also see how much power draw varies as a function of CPU load. The section labeled "Application Crash" is when the spider that uses the majority of the CPU time on this box crashed.
 

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fake-name

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2018-09-10 19_31_53-Grafana - Weather Logger - Iron.png
Ok, wow, overall savings of ~50 watts.

It went from ~280W average to ~230W average.
 

vl1969

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Feb 5, 2014
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looks nice.
I have a SM846A case where I dumped the PSUs since they where too loud and not certified.
didn't go with originals as they are expensive for my setup.
just cut out the back window and fitted a regular ATX PSU.
the original was PC cooling and power silencer 760W 80 silver, went out on me a few weeks back so now I have
PC cooling and power 1050W 80 gold certified fully modular, that cuts down on cable mess :).

not a perfect fit as PSU is to wide to fit flash to the back but still nice. when I have time I take some pictures.