About

Michael Zucchi

 B.E. (Comp. Sys. Eng.)

  also known as zed
  & handle of notzed

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Sunday, 29 March 2020, 08:01

New PC Gets a Box

I finally built a box for the computer I bought back in December.

It's very red. Not quite AMD red but I had the paint from the speakers and it's still AMDish. It cost $90 for a litre, you might be seeing more of it.

I made it out of 12mm MDF. MDF really sucks, it's heavy and it's fragile but its' cheap and available - here in Adelaide you can't get much (for any decent price) and I don't have the machinery to dress wood anyway.

Because you need to take the lid off to get to the insides you can't just screw into the MDF directly, partly with 12mm board. So you need to get some way of strengthening the wood.

The threaded-insert 'nut' screws into wood using an Allen Key and the M6 bolt goes into that. It means you can screw and unscrew many times without fowling the wood.

The only part I could find locally was an M6 screw insert but it requires a 9mm hole so it's too wide for the 12mm MDF. So I had to create wooden lugs to mount these. I was going to try using MDF but it just seemed like too much risk with such shitty wood and it would make drilling the holes more difficult and require more days for glue to set and so on. I used some salvaged scrap and mounted them using 2 screws to the MDF (and glue).

The initial design document and cutting plan. Initially I was going to mount the fans externally but changed my mind. I also kept thinking I was working with 11mm MDF hence the 172mm front panel (needs to be 174mm!).

I started with a 450mmx1800mm piece and used under half - I got my brother to buy it when I was on crutches and I hadn't worked out a design yet. I cut 2x280mm pieces, which I then cut a 150mm strip from each - these became the sides and top and bottom. Then I cut one more 174mm strip which became the front with a small piece of scrap. Basically the sides go the full length of the case, and front end-caps everything.

The outdoor workshop. The weather was nice so I took advantage of it. My shed (quite new) is not ready yet and full of dust and shit and doesn't have a proper floor.

So I didn't take any photos until I had the box nearly done so I'll briefly describe the steps. First I cut all the pieces and sanded down the edges. In particular the top and bottom pieces had to be true and square on at least 3 sides. I worked out where I was going to mount the top fans and cut the holes for those using a jigsaw, a compass helps to centre the circle properly.

I don't have any corner clamps so instead i used a square and a square piece of wood (the 'scrap' from the cutting) to align one piece at a time, glue and screw, clamp, and leave overnight to set. I did that for the bottom first. Then I did it with the top, also ensuring it was parallel to the bottom and square to the front. And finally the front could just be screwed and glued on. Fool: I didn't roughen up the flat of the MDF enough so the glue isn't as strong as it should be - after all the painting and sanding the rear top began to split off but only a few mm worth (I'd kept the screws out while I was painting).

I had intended to use some dowels, I even bought an overpriced dowel jig for the purpose - but I bought the wrong sized dowels (I think they were on the wrong hook in the shop and I didn't check) and the dowel jig was absolute junk. I got one OK hole and then it wouldn't sit in the right place. Helped by the fucking shitty 'dowel drills' which I also bought which just weren't straight. $130 down the drain basically. Fuck Bunnings. Why does everything they sell have to be fucking junk.

Once I had a box to work with I set about solving how to mount the side panel. I cut a strip from a bit of old wood and then made lugs out of them. For the threaded insert I did an 8.5mm hole deep and a 9mm hole half way for an extra-snug fit. It was tricky screwing them in straight. Idiot: I should've spent more time squaring up the strips! Luckily it's good enough.

I decided to go with screws to mount the lugs, which I countersunk. The screws are just at the limit of fitting within the 12mm MDF but they seem OK. Later on I glued them in place as well.

I drilled the holes in the front panel. First a couple by measurements then I made a pin to drop into the inserts which marked the spot. I should've got some dowel markers - should've just got those instead of the shitty jig in the first place. Mistakes were made, not the last. I countersunk them to match the stainless steel bolts and then screwed it all together.

Then took a couple of afternoons to sand it all square.

Next was positioning and mounting. The hard constraint was at the top - where the fans go. At the bottom the GPU and the lugs collide so that set another hard limit, and the PSU just had go to where it fit. I think I should've positioned the mounting board a bit further toward the bottom (right) but it's no big deal and something that isn't too difficult to change.

Lets hear it for the fans.

The base-plate was from an old PC I took apart years ago to build a small case (which I never built), I'd chopped it up for an ITX board with a single slot which just happened to be almost exactly right but I did trim it a bit further to give more options for the PSU. I just screwed it to the wood with tiny screws.

PSU mounting details. Also a good shot of the threaded insert mounting lug for the side panel.

The PSU was more work, I went through a couple of ideas but settled on a pair of brackets. A small angle on the bottom and a corner bracket for the top, leaving room for cables, airflow and any front-panel stuff behind it. The power cord was quite a problem, I had to hack away most of the cable support plastic and even the front so the IEC plug pushed in far enough and the wires didn't stick into the fan. At the time the modular power cables from the output were pressing up against the GPU so I couldn't move the PSU any further away from the fans - but with some adjustments I made more room. So the PSU could potentially be moved but I haven't done so and the IEC cable would still need some hacking anyway.

Everything in place, doing some heat testing.

It took me a while to work out how to create support for the PCI bracket. A flat bit of metal? Some angle? The problem is that the IO panel and the GPU and the rest of the design mean I can't just use a piece of wood as the back plate as there isn't enough support area or there's no way to then get the computer together. And that means any PCI support wont be well supported either. I toyed with using the PCI mounting plate from the computer I'd chopped up but I couldn't quite work out a way to mount it (actually in hindsight this is one reason the base plate is where it is, it was just enough for 4 slots with the board against the base). That probably would've worked but instead I went with using a piece of square tubing. I cut a slot out at the bottom of the tubing so that it slides onto the end of the PCI bracket, and then I use another pair of lugs to mount the bar to the case.

It's a bit tight and probably slightly out of position but it's solid and supports the card well.

So I put it all together and started doing some heat testing. I made some vents in the side panel based on the position of the GPU and other constraints like the mounting lugs. The upper vents align with the GPU vents on this particular GPU.

The idea is the bottom ones feed cold air to everything and the higher ones can vent some GPU exhaust if they get hot. In practice air just seems to come from all of them. My GPU fan never goes above the bottom rate anyway, I don't play games so it isn't doing much more than running the desktop now.

More heat testing.

I normally run eco mode (65W) on the Ryzen 3900X, but I turned that off to try it out. Running blender and the Mandelbrot OpenCL stuff from the previous blog the CPU got up to about 81C and the GPU in the 70s. There was a bit of a hot-spot near the front end of the GPU but it didn't seem too bad.

On the other hand the cables were stuffed in pretty badly, particularly behind the PSU and up against the GPU. So I worked out a way to fold them and tie them up and it improved airflow quite a bit. I also chopped up the HDD cable from the PSU and soldered on one of the fans - this motherboard only has a single fan header, and I got the PWM fans. It works better if they're both on 'flat out' anyway - they're only low rpm fans and it keeps the CPU cooler so it makes less noise. There's a shot later with this one.

Second undercoat drying.

Painting. It sucks. You paint, you clean, you sand, you paint, you clean, you sand. Makes a mess. Stinks. Expensive.

Actually before I painted it I detailed it.

After final coat. The enamel needs sanding with wet and dry sandpaper with water, otherwise it clogs up the sandpaper. Water and red dust just makes more mess.

And I fucked it up quite badly. 1x coat of sanding sealer, 3x white undercoats, and 3x enamel overcoats ... but the final overcoat is full of dust and hair and bubbles and isn't even enough. It could probably be fixed with a sand and recoat - but I just gave up.

I worked out later at least one mistake I made, shaking up the can rather than stirring it aerated the paint which came out when I used a roller. Oops.

Before I painted it I decided to cut matching slots on the other side panel, to help airflow a bit more but mostly for aesthetics. And of course I totally fucked it up - I put the upper slots in the wrong place because I measured from the inside and not the outside. Fucking idiot! That really pissed me off for days but what can you do eh? The base plate was always going to cover some of the upper rear slot but I could've cut some of it away, but I just gave up.

Here I've mounted the power button as well. I don't know what to do for the button - it's a bit fiddly making anything that will push onto it, but it works as a 'hidden push-button' hole in the case anyway.

I decided I should probably cover the fans, don't want a stray screw falling inside or something. I used some aluminium fly wire.

Nearly finished, fans, motherboard, power supply. Here the cables have been tidied up. The reset switch is just hanging out the back for now.

And that big-arse GPU is in now too! After tidying up the cables there is ample room.

I also detailed the galvanised square tubing - I ran a wire brush over it with the drill to give it a satin finish and then put on a couple of coats of Penetrol. I haven't used it before but it's supposed to be 'the shit' for a natural metal finish (I got it for my kilt belt buckle but haven't used it yet). The steel bar doubles as a mounting point for the magnetic antenna that came with the motherboard.

Due to the issues mentioned earlier there's no rear panel yet. Maybe i'll do some steel and attach to the bar or something. In hindesight the case could've been another 15mm long so the bar could be recessed ... but it's too late now (unless I get a shorter GPU). The case could have been any depth!

Despite 24 hours drying in good weather the Penetrol and paint were still a little tacky feeling (or rather, set but soft). Because of this I only did up the screws lightly, but perhaps I should've waited a few more days for the paints to harden more. I also should have sanded down the internal surfaces where the paint created a thicker edge too, already a couple of bits have pulled off but they're inside.

That's it!

It is still on the dining table because my computer desk is occupied with junk, my old Kaveri machine, and a giant old full-tower from work.

Tagged biographical, hacking.
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