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Homemade Mini Case for LC, P475, Q605

bigmessowires

Well-known member
20170705_205849.jpg

Here's my entry in the "design a custom case" bonanza! Like Trash80toHP_Mini, I'm making a case for the LC series pizza-box computers, which also includes the Performa 475 and Quadra 605. It'll be just the logic board, power supply, and SCSI2SD for main storage. No fan. No floppy drive, but there's a cut in the case for running a cable to an external Floppy Emu. Currently no built-in speaker, but I might revisit that later.

The power supply will lay flat next to the logic board, just like the Apple case. The SCSI2SD will be folded over backwards, and will lie upside-down on top of a shelf, just above the logic board (or the PDS card). The photo shows how the parts will be oriented when they're inside the case.

lc-case-1.0.png

Above is the plan for the laser cut acrylic pieces. It's a six-sided box constructed with tabs and slots. Nuts and screws in the T-slots on the sides will hold it together. The piece in the center of the diagram is the bottom of the case. There are three screw holes for securing the logic board, and a square hole for a zip tie to secure the power supply. The zip tie will come up through the square hole, over the PSU, and down to the matching notch at the left edge of the bottom piece.

The piece at the bottom of the diagram is the rear panel. I didn't try to route out each port individually, though I might later. For now it's just one long opening for all the ports, as well as openings for the power plug/switch and for the PDS card's connectors.

The front piece is pretty boring, except for an odd square cutout to accommodate a screw that sticks out on the end of the power supply. One of the tab slots is also extra tall, to provide a spot for the floppy drive cable to sneak outside the case.

The piece at the far right of the diagram is the shelf. Imagine it sitting inside the case, separating the right-most interior region into lower and upper sections. The lower section houses the PDS card, and the upper section houses the (upside down) SCSI2SD. The cutout in the shelf is for the SCSI cable and 4-pin molex power connector.

I spent a lot of time with calipers, measuring everything as accurately as I could, so there's not a single millimeter wasted. Unfortunately there's still some dead space in the area behind the front piece, because the the PSU's depth is greater than the logic board's depth. You can see this in the layout photo. Maybe this dead space could be reworked to hold a small fan or 8 ohm speaker.

Did I forget anything? I hope to send this off for laser cutting tomorrow.

 

Trash80toHP_Mini

NIGHT STALKER
Feets

Seriously, you need to provide for them. Support your case as a tower with the PSU on the bottom. The case itself needs to be as tight as you can make it on front and back panels. Front bezel sounds like it's easily done. rear needs to have the RFI shielding in place at the minimum if you're not going to do your port cutouts on the first pass.

If you're not including a fan you'll need to induce convection cooling using the expanded hot air pulled through the PSU and vented out the topside of your case configured to act as a MacChimney***** It's not an ideal situation, but it'll be hella cooler than the 128k's feeble attempts at convection cooling.

***** MacChimney's not one of my playful retro-tech-naming conventions for things. It was a real product (made of cardboard?) that sat atop the Compact Macs. It looked silly, but measurably increases cooling airflow through the woefully inadequate fanless cooling of the Compacts. Think redonkulous wide brimmed, silly skinny Cat in the Hat sendup on the Dr. Seuss illustrations.

the-cat-in-the-hat-dr-seuss-1-0-s-307x512.jpg.13fd005dcd487d6ea3b806c11b91b874.jpg


 
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Trash80toHP_Mini

NIGHT STALKER
One last notion:

Consider adding a tad of height to your tower design.

Configure the chimney's flue openings at the top as a series of circles, each surrounded by four holes.

A series of tiny, ultra thin 12v fans running at 5v probably won't put out but a few dB, should they be necessary.

See if you can get a better deal on two sets of cutouts.  [;)] ]'>  Seriously, I've got the Q605 back together on the bench to do a complete rundown on video output resolution/frequencies. If I can't choke 60Hz out of the little beauty, I'll be switching back to the 630/6400 project. I'm really likin' what you've come up with there, and I've got MicroQuadras to spare.

 
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MJ313

Well-known member
Would it be possible to replace the power supply with something smaller, like a PicoPSU with some sort of ATX conversion?

http://www.mini-box.com/s.nl/sc.8/category.981/it.C/.f

Getting that relatively chunky power supply slimmed down would allow for a seemingly smaller/tidier footprint.

I think Q605's max power draw is something like 30W? Anyone got a more accurate number?

The economics might not be there, but the "cool factor" might be. Dunno.

 

Trash80toHP_Mini

NIGHT STALKER
Hiya, mj, with the fans installed in place of the convection cooling that's a definite possibility. Maybe some cubic saved even after offsetting their added height.

For a first pass at a build, it's probably better to stick with the real deal, especially if a silent convection cooling system will be a design aim. You need more than that little bit of heat bit to get a chimney going. Think fireplace lighting sequence: a bit of smoke gathers about the in the firebox and even leaks out into the room before there's enough air expansion to begin to pull it up and out the flue.

Dunno though, I'm a jackleg engineering type, nowhere near being the real deal. These are fairly well informed guesstimates as are all my suggestions. Corrections welcome!

 
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Trash80toHP_Mini

NIGHT STALKER
First results are in for the Q605 on the VGA/SVGA setting I tried first on a lark.:

Mag Innovision test bench 21" CRT w/Resolution/Frequency readout LCD/Mac DA-15, HD-15 and 5BNC inputs

ENHANCE "Liberty Wheel" DA-15 to DA-15 VGA Adapter between Q605 and DA-15 input

640x480@60Hz VGA - gives me an offset image and N"on-Registered Mode - See Setup" error code.

- Monitors Control Panel lists it at 640x480x60Hz though.

I can confirm lowendmac's field reports of 800x600 output!

800x600@56Hz SVGA - Image is fab, can switch resolutions on the fly.

-Gotta check to see if rPi 800x600 SVGA LCD kit can tolerate the sub-standard frequency. :-/

I'll test it on the 15" 60Hz ONLY HP LCD I keep around for testing purposes first.

 
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Trash80toHP_Mini

NIGHT STALKER
If you layout the fan cooling mod I suggested, you could reserve cubic in front of the fans for your Floppy EMU's buttons and readout on top with the Snow White floppy slot on the front.

I still want one whatever way you go, me loves your prototypes. [;)] ]'>

 
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Nathan

Well-known member
The "pizza box" is pretty mini as is. If one ditches the floppy and harddrive for a floppy emu and a sd2scsi it'd be VERY mini. Have you considered making an access port on top so you can get to stuff after it's assembled without totally taking it apart. Frankly a slide out tray for the motherboard would be awesome too.

 
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bigmessowires

Well-known member
I'm not worried about getting everything perfect the first time. I'd rather just get something built, then refine the design based on results of the first version. I'll share the design files with anybody who wants them, so you can order one for yourself direct from Ponoko.

Feet: Don't want 'em. But rubber stick-on feet are easy to add after the fact.

RFI shield: For actual electric shielding, or for aesthetics? I don't think it's really necessary, and I don't have one, anyway. :)

Tower: I prefer a desktop case, but to each his own I guess. A drawback of the tower is that the base needs to be wide enough so it won't easily topple over. For this case layout, that would require increasing one of the dimensions, and a larger total case volume than a desktop case.

Cooling: Maybe I'm stupid, but I'm not really worried about cooling. There's no spinning hard drive or floppy drive to add heat here. I frequently use LCII and LCIII logic boards and power supplies sitting bare on a desk, with no fans or convection cooling, and never noticed them getting more than slightly warm. I probably need to add some vent holes somewhere, but I'm optimistic it'll be fine with passive cooling. I'll use an IR temperature sensor on the first prototype to see if it gets too hot, and adjust things if needed.

Dimensions: The left/right side pieces in the diagram are 56.1 x 214 mm. Those are the only pieces that are all slots, no tabs. I can send you the Inkscape design file if you want it, but I'd suggest holding off on building anything from it until after the first test fitting.

Pico PSU: I like this idea a lot. It would help reduce the footprint of the case in both X and Y dimensions, for a significant total reduction in volume. If you haven't seen the Pico PSU, it's barely any bigger than the ATX connector itself:

picoPSU-80-b.jpg

But you'd have to use an external 120V AC to 12V DC power supply, which is roughly the same size as the stock Apple PSU. So you wouldn't be saving volume, as much as moving volume from inside the case to outside. Still, an improvement.

12V-12.5A_350.jpg

The stock Apple PSU supplies are shown here:

q605-psu.png

+5V, max load of 3.75 amps

-5V, 0.075A

+12V, 0.78A

The cheapest Pico PSU 80 is more than capable of doing that job:

pico-psu-80.png

My only concern is that the Pico PSU doesn't mention anything about -5V. I'm pretty sure it's there since it's part of a standard ATX connector, but it's not specced. I sent an inquiry to their sales support email, but haven't received any reply.

Pico PSU would also probably help a lot with reducing the heat inside the case, if that's a problem.

The combination of Pico PSU 80 and 12V/12.5A external supply is around $50. I'm going to stick with the stock Apple PSU for this first version, but I'll definitely be thinking about the Pico PSU for the future.

One other power supply thought: the stock Apple PSU puts out three different voltages. But I'm fairly certain I won't need the +12V if I'm not using anything with motors like a hard drive or CD drive. I don't know what the -5V supply is used for: the internal speaker amplifier maybe? I'm going to guess I can live without it. So it might be possible to power everything from a single +5V/3.75A external supply, with no power supply at all inside the case.

 

Nathan

Well-known member
Without the RF shielding it's probably not FCC certified anymore. Electrical interference is a thing, but I don't think you'd be able to conclusively identify the lack of it as the cause if you had a problem. Might be an issue if you want audio out. I know speakers can pick up interference normally, but maybe you could get interference before the output if the computer isn't shielded? Not sure if grounding is affected. I bet the PSU you mention doesn't provide the -5v if it's not on the spec. From what I've read the -5v is in the AT standard, but not in the ATX standard (or maybe that's the ATX12V standard). You should never assume that it's not needed unless you're 100% sure what it was originally needed for, though. As you say it may be chiefly for the drives though.

 
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Trash80toHP_Mini

NIGHT STALKER
RFI was a very big deal for computer certifications when there were analog televisions scattered about in neighbor's apartments acting as detectors.

If RFI does turn out to be a problem, the inside of the case can always be gilded with aluminum leaf, or variegated "gold" leaf. Security tape for windows type contacts set in place as tabs would then be grounded.

Varnish with crinkled, flat, glossy or matte patches of aluminum foil stuck to it on inside or outside the case would work. It'd be burning man cool too if applied in an assortment of treatments randomly..

Big guy, if you're going for desktop mode, the rectangle in the back is your air inlet. Add cutouts for six missing colored logo slices directly above the CPU for your outlet. I suggest a banana shape. [:eek:)] ]'>

 
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bigmessowires

Well-known member
OK, I've added some vent holes, and ordered the case parts. $50 worth of laser cutting excitement! It should be finished next week.

I traced the -5V supply as far as an AM26LS30 chip, which seems to be the output driver for the serial port. I know the Mac's RS-422 serial ports use differential signaling, but I didn't think they required negative voltages. Oh well... I'm sticking with the stock Apple PSU for now, so it doesn't matter.

Since I'm mounting this whole thing in a plastic box, I've pretty much abandoned any pretense of RF shielding. Yeah, maybe it'll interfere a bit with my neighbor's garage door opener and cordless phone, but I'm not too worried. :)

For the cooling and venting: I added more vents than I think I probably need, and I also added a few holes in the top where I can take temperature readings with an IR thermometer. Assuming it doesn't overheat as-is, I'll try covering up different combinations of vents, to see how much each one contributes to cooling. I can save a few dollars in future laser cutting fees if some vents aren't necessary and can be eliminated.

 
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Trash80toHP_Mini

NIGHT STALKER
I've got most of your parts printed and spraymented to corrugated cardboard to play with tonight at work.

3D model pics for11:00 news  .  .  .  time zone unspecified.

 

bigmessowires

Well-known member
That was a great idea printing the images and mounting them on cardboard! Looks good! Do the dimensions seem about right? How about the openings in the back panel for the ports and PDS card?

Looks like it's the same width as the regular Apple case, a little bit less tall, and a lot less deep. Maybe 60% of the depth of the Apple case? I don't have any LC or Q605 cases here, so I wasn't able to do any direct size comparisons. I only have a spare logic board and PSU as reference.

By the way, I got an answer about the Pico PSU and its -5v supply: "Dear Customer, the picoPSU does not have a -5V output because it is no longer used. Should you need other details, please contact us!" So by itself, the Pico PSU couldn't fully powered a Q605. If I had to guess, I'd bet everything but the serial ports would work though.

 

Trash80toHP_Mini

NIGHT STALKER
Thanks! It's fun prototyping something really big from pen plots off the vinyl cutter, but cutting all the tiny slots out of something this small was a great distraction at work when it got slow.

Didn't comment on how great everything looks last night. I was tired and realized the pics I'd taken and sized for posting didn't really show the 1/2"+- width reduction or the fun side of the case. Corrugated is a bit more than 4mm fat and very frumpy lookin' compared to the real deal. Had to smoosh the tabs to get them to fit the slots, so the plexi should make it a few mm smaller overall and a lot more svelte than my mockup.

P7070613.JPG

P7070615.JPG

I was wrong about needing the RFI shielding for the @$$bits. The connectors are so closely spaced that the airflow reduction would only be needed if you were on the very ragged edge of the limits of convection cooling.

Sound familiar? :D

Looks like you've got the cubic for a thin fan on top or a pair of tiny ones on the front bezel. LOVE the captured nuts for the bolts holding it together. I'm so used to drilling and tapping holes for the bolts I or solvent welding the parts that I wouldn't have thought of that. Score 1 for the laser cutting production process.

Post a PDF of a mirrored image of the file so I can sprayment printouts to the outside of the cardboard box. Add a 10% gray fill to the case and 50% to the slots, vents and holes. Add a 1cm x 10cm reference box to the file for easy scaling.

Feets for the convection cooled tower version would be extensions of the front and back panels on the PSU end:

     ____

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 __|      |__

|_----------_|

Lovin' your work, Big!

 
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