A new backplate showed up at my door today...

General discussions related to the Altair 8800 Clone

A new backplate showed up at my door today...

Postby steve_a » June 8th, 2018, 5:04 pm

After about a month of measuring, drafting, measuring, modeling, ordering, measuring, and shipping a new backplate showed up for my machine today. For installing a micro ATX based motherboard (and other gizmos) inside.

20180608_142724.jpg


20180608_141702.jpg


I used 20mm motherboard standoffs for power cable management. This set where the micro ATX I/O panel and PCI cutouts needed to go.

Two 92mm fans fit on the back. One of the 92mm sections was made big enough for an Asetek 545 LC liquid cooler. So one's installed. The fan for it isn't on yet -- that's later.

The Altair's DB-25 serial ports are still there (natch!) There *should be* room for the cassette interface under the motherboard. But I don't have one (yet). So the audio jacks and DB-25 for that are already cutout.

I have a 5-bay 3.5" Hard Drive Cage to put in for bulk cold storage. That's also later.

I'm still waiting on an ATX power supply and a 5v-12v boost converter -- I'll be using the 5v standby voltage from the ATX power supply boosted to 12v for the Altair Clone. You can draw something like 3A through the standby and the Altair needs a whopping 40mA, so I think that'll do fine. I didn't want to order the power system until the backplate showed up and... you know... fit.

The motherboard installed right now is fried and not permanent. So once the power and cooling is in place the Altair will go back on its shelf and do its thing until the computer currently acting as a terminal needs replaced. Then its time to buy motherboard, processor, RAM, and video card.

Once everything is all installed and happy, I plan to share my dimension drawings. It's not perfect (thank God for ATX wiggle room), but if anyone else is interested I'd like to share the fruits of my labors -- assuming the power supply fits. This wasn't the cheapest thing in the world to get cut and bent, but the shop I went through offers discounts on volume orders. So if there's interest I may order a few more and sell them on eBay or something. If there's interest.
Last edited by steve_a on June 11th, 2018, 12:25 am, edited 1 time in total.
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Re: A new backplate showed up at my door today...

Postby toml_12953 » June 9th, 2018, 6:09 am

I'll buy one if they become available!
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Re: A new backplate showed up at my door today...

Postby AltairClone » June 9th, 2018, 9:48 am

Looks great! Did the pre-drilled holes in the Clone case bottom line up correctly with the micro-ATX board? I never had an opportunity to test that. Some of the mounting holes are under the bottom flange of the original rear panel. I assume you made cutouts in the bottom flange to expose those mounting holes?

Very interesting - keep us posted.

Mike
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Re: A new backplate showed up at my door today...

Postby AltairClone » June 9th, 2018, 9:57 am

steve_a wrote:I'm still waiting on an ATX power supply and a 5v-12v boost converter -- I'll be using the 5v standby voltage from the ATX power supply boosted to 12v for the Altair Clone. You can draw something like 3A through the standby and the Altair needs a whopping 40mA, so I think that'll do fine.


If you’re not going to use the 12v fan connector on the Clone PCB anymore, then the PCB can easily run from 5v. One jumper can be tacked onto the back of the board to bypass a zener diode and the Clone will run from 5v. Let me know if you want more info about that.

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Re: A new backplate showed up at my door today...

Postby steve_a » June 10th, 2018, 10:38 pm

toml_12953 wrote:I'll buy one if they become available!


Hey, right on! I have a few tweaks I want to do to this one -- I'd like a hair more space between the motherboard and the inside of the plate, and I think having the top flanged like the stock clone would be beneficial.. after hanging coolers and fans on it I'm already seeing bending. But I'm sure it'll hold up. There's a couple other measurements I'd like to update, but I'll keep everyone in the loop when I get ready to order a set of 5 or so -- I don't know when that'll be.

AltairClone wrote:Looks great! Did the pre-drilled holes in the Clone case bottom line up correctly with the micro-ATX board?


Like a champ. I used standoffs with female ends on both sides so I could keep everything loose before tightening the board down. And it all lined up swell in the case. I had about 1/16" all around of wiggle room, and I needed all of it to make room between the motherboard and the plate for a PCI card (not pictured, it fit too though). That's one of the things I want to adjust on the next go-round.

AltairClone wrote: I assume you made cutouts in the bottom flange to expose those mounting holes?


Sure did... eyeballed it :-P:
20180610_200925.jpg


It seems I'm about 1/16"-3/32" too narrow altogether, and on top of my other gripes I also left myself gobs of extra space around the aluminum siderails that really isn't needed.

I still have to fit in the power supply, once that's squared up I'll be revisiting my dimensions and such -- shouldn't be too terribly long.. couple of months, maybe?

In the essence of open-source (of which I will always be a champion) and homebrew clubs of yore: Here's my dimensioned drawing of this plate -- I converted to png from pdf so I hope its legible. I also have the CAD files if anyone wants them.

backplate_rfq_20180514 Rev(-) - DIMENSIONED.png


AltairClone wrote:If you’re not going to use the 12v fan connector on the Clone PCB anymore, then the PCB can easily run from 5v. One jumper can be tacked onto the back of the board to bypass a zener diode and the Clone will run from 5v. Let me know if you want more info about that.


Sure! The boost converter I have isn't the greatest in the world, and if I could get away with using only the standby voltage I'll do it!
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Re: A new backplate showed up at my door today...

Postby AltairClone » June 11th, 2018, 2:43 pm

Tack on a jumper wire where shown by the yellow line to configure the Altair Clone PCB to run from 5v instead of 12v.

Mike

5v mod.jpg
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Re: A new backplate showed up at my door today...

Postby TomXP411 » June 14th, 2018, 11:31 am

So this is exciting. I have been thinking about building another PC for work and retro development; I've been using a NUC, but this is an even better way to go!

If we can get enough people to do a Massdrop-style order, I'd be interested. How much did it cost for the one-off you had made?
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Re: A new backplate showed up at my door today...

Postby steve_a » June 26th, 2018, 10:16 pm

TomXP411 wrote:How much did it cost for the one-off you had made?


It wasn't cheap, just the one cost $300+.

I think I can get individuals down to $120 or so (I lost the quote) if I ordered five of them. I do want to make some alterations if we do order more.
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Re: A new backplate showed up at my door today...

Postby toml_12953 » June 27th, 2018, 4:54 pm

steve_a wrote:
TomXP411 wrote:How much did it cost for the one-off you had made?


It wasn't cheap, just the one cost $300+.

I think I can get individuals down to $120 or so (I lost the quote) if I ordered five of them. I do want to make some alterations if we do order more.


You can put me down for one if you're making up a list.
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Re: A new backplate showed up at my door today...

Postby TomXP411 » June 27th, 2018, 5:03 pm

steve_a wrote:
TomXP411 wrote:How much did it cost for the one-off you had made?


It wasn't cheap, just the one cost $300+.

I think I can get individuals down to $120 or so (I lost the quote) if I ordered five of them. I do want to make some alterations if we do order more.


Ouch. Yeah, I don't need one quite that badly. I have been actually using this system with a Raspberry Pi as a terminal; I just leave the Pi inside the case. So I will just try to locate some port adapters to mount an HDMI and USB jack in two of the DB25 socket openings.
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