Low-Cost, Complete ECB Enclosure Design [message #7778] |
Wed, 10 June 2020 11:30  |
farmerpotato
Messages: 3 Registered: May 2020
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Junior Member |
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Hello all,
This is my first post. I'm very interested in learning from this community, and I hope to contribute back.
I am constructing a ECB computer around the TMS99105. It will be backwards compatible with the Geneve 9640 and TI-99/4A, and share a good deal with an MSX2, like the V9958 and OPL3. All the cards will be available separately as open-source. Hopefully they can work with other CPUs, and I can use existing ECB cards like the V3 Disk IO.
This post is about the low-cost enclosure I am designing for it. Where low-cost is around $150.
I would appreciate feedback on the ideas I have so far. Especially on how to get the cost down.
I am using the 8-slot ECB backplane from jcoffman,
The backplane is mounted on some flat rails I saw at Electronics Goldmine.
The $7 rails were ideal, at 17" long, 0.4" wide with 0.2" spaced 4-40 holes. Obviously I will cut them to length. I have not found any other source for this! Extruded aluminum Eurocard rails are way too expensive! (The rails were $3 on sale.
The box will be a standard Hammond enclosure like the 1458VD5B, 8x8x5", or the 10" wide 1458VG5B. It is a very nice Altair blue!
The rails fit into the back panel holes, horizontally side-to-side. But vertically, one rail is off by 1/2 a hole or 0.1". Argh! I don't know what kind of bracket would fix that, but maybe it's enough to use a cotter pin or bend a nylon standoff?
The card guides will be common $1 PCI guides from Bivar, though the snap-in pegs are a big too large.
What I have assembled now:

(Card guides were from a junker PXIe chassis--those cost $5 each, so I will use the boring $0.80 kind.
(second backplane is just a stand-in for a card)
I may just use acrylic sheet, laser-cut with precise holes, to hold the card guides, supported with metal.
Cost for the enclosure is about $50, so that leaves a budget of $50 for all the other parts.
In the 8x8" enclosure, there is just enough room for power and fans. Power will be a $35 pico-PSU. For cooling, some <10mm fans underneath, or a blower on one side vent. (are there squirrel cage blowers that can reverse-suck air into the blower?
Here's how low-cost is working out so far:
$ 20 Backplane, 8-slot
$ 50 Enclosure, Hammond 1458 series, 8x8x5" or 10x8x5"
$ 13 Card Guides
$ 25 PicoPSU
$ 21 Steel rails ($9 on sale)
$ 10 Acrylic, laser-cut (by me)
$ 10 Fans
$ 10 Misc hardware (screws, brackets, Mate-n-Lock, etc)
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$159
Additional labor will be milling the front aluminum faceplate, to expose front panels, and holes in the back faceplate.
There could be an option to use a common PC tower as the case, mATX or Mini-ITX. Maybe the cage could mount in one. I didn't get far on that; how would the PCI brackets work?
I hope to offer this as a kit.
I will post more as the computer is built - PCBs are in the mail.
-Erik
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[Updated on: Thu, 11 June 2020 10:48] Report message to a moderator
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