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Mark-8 boards on ebay

For something as scarce as a Mark 8, you are better off waiting for someone to make or making a reproduction, yourself, than mucking with original boards. Since the holes are not plated, and the artwork was published, you could etch your own PCBs at home, and it would be lot less expensive than buying a set of PCBs.

regards,
Mike Willegal

falter said:
Yeah. I'm kinda torn.. if those are original they are pretty close to pristine.. how many pristine as-sold original pcbs are you likely to encounter? Feels like anything you did to them would take their value down, especially if you screwed anything up. And even if you built them into a machine it'd never be an 'original' Mark-8.. it'd be more like a new Delorean. Plus some original parts just aren't available as I've learned with my TVT project.

Hmmm. I had this debate when I saw an original set of TVT boards that I narrowly missed. $38 though. But even then, I was torn between 'oh it'll be an original TVT' and 'no.. it'll still be mostly a repro from 2016 and now no one will be able to see how the original boards came from factory.
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falter said:
That was one other thing I meant to ask. *Are* there Mark-8 examples out there known to have *not* been built from the kit boards, but rather via the plans? I know the artwork was available in the plans so it was theoretically possible to make your own boards.. wondering if anyone did.
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The Mark 8 isn't that dense, circuit board-wise. I can well imagine that there were those who simply used wire-wrap or even point-to-point wiring. PCBs were a little more involved back in those days. If you worked for a manufacturer, you were used to tape, india ink wite-out on mylar sheets, often photo-reduced before going to PCB. Back then, I had a Kepro PCB kit and made a few PCBs of my own, but between drilling and layout, it was easier to wire-wrap.
 
There are high-quality scans of the original PCB artwork here - http://www.bytecollector.com/m8_docs.htm

Image to Gerber converter here - https://imagetogerber.wordpress.com/

I don't think these boards would be hard to etch at home, but having Gerber files would be nicer.

If I were doing it I'd use something like OpenCV to centroid a couple of the round pads and scale/rotate the scanned images to match the actual part pitches and be orthogonal and lined up through the 2 layers.

Drop a hole at each of the required locations in a Gerber editor and you're done.
 
I'm comfortable with using the original artwork.. provided I can get the correct dimensions. I had the thought to do something like what you suggested with my TVT project and then do soldermask and so on but I decided I wanted to stay true to the original design, even if it's not perfect. The ASCII encoder worked beautifully (thanks to Chuck and Dave et. al for their help!!). It just looks right.

My problem with doing a Mark-8, apart from getting scale right and the challenge of a dual sided board, is I really do not like the look of modern PCBs at all. For the TVT this isn't so critical since a wide array of PCB material was used by hobbyists.. but a Mark-8 has a certain look.
 
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Older PCB material was flourescent, which screws up modern PCB processes. Hence, it is not made anymore.
Finding enough old stock for a Mark 8 type project is likely to be challenging.

The artwork was published back in the day and is available on the web. Why not use what the original do it yourselfer had available. Dimensions are easily determined.

Regards,
Mike Willegal


falter said:
I'm comfortable with using the original artwork.. provided I can get the correct dimensions. I had the thought to do something like what you suggested with my TVT project and then do soldermask and so on but I decided I wanted to stay true to the original design, even if it's not perfect. The ASCII encoder worked beautifully (thanks to Chuck and Dave et. al for their help!!). It just looks right.

My problem with doing a Mark-8, apart from getting scale right and the challenge of a dual sided board, is I really do not like the look of modern PCBs at all. For the TVT this isn't so critical since a wide array of PCB material was used by hobbyists.. but a Mark-8 has a certain look.
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Corey986 said:
View attachment 33492
How old do you think this Scelbi board is?
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not that old.

modern electroyltic and trim pots are too dark. old ones are lighter blue

extremely good registration of the holes.

You had to be working with a really good board house to get them to digitize your holes
with that accuracy. Back then, as Chuck said, you were using mylar and tape, and when you sent
your board out, they had to digitize the drill locations. Gerbers didn't exist in the hobby space.

at the price of gold back then, you'd gold plate even proto runs.


the other think looking at it is there is no water mark on the FR4

I'm assuming this is dyed modern stock?
 
The consistent spacing/alignment of the tracks & components, plus the consistent "sharpness" of the 45 deg angles of the traces, show the board was laid out on a CAD system. It looks good, too good for a hand layout. Most of the old boards had a few "meandering" tracks on them.

Tom
 
falter said:
I'm really surprised there isn't like, 'vintage copper clad PCB stock' out there somewhere. There's virtually everything else but that. Ought to be a business there for someone enterprising enough.
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I've got enough to just about tile a basketball court in the warehouse. We've used it for toner transfer boards, I used a fair bit of it in college for projects. It requires a cleaning to remove the copper oxide before you use it. If this is something people want, I can see about listing some of it. We've also got a 48" metal shear in the machine shop, so it can be sheared to desired size for e.g. OSI boards or Mark-8 boards. There's double-sided, single-sided, "clear" FR4 (natural resin color I guess, it's translucentish whiteish...you know, like old boards!), green FR4, and phenolic.
 
I would be all over that. Let me know if any of it becomew available for sale. I'm looking for single and double side with tht vintage green color like the original TVT and those Mark-8 boards.
 
Most original SCELBI PCBs did not have gold plated edge connectors and though the practice varied with builder, for the most part, only the SRAM boards were socketed.

A good image of an original SCELBI CPU board can be found on my SCELBI registry page.

I'm not so sure about doing a Mark-8 board set. I was wiring a SCELBI keyboard interface enclosure tonight and said to myself, "my next project is not going to require so much point to point wiring!". Between the two SCELBI chassis I have built and the peripherals and cabling, I must have soldered something like 500 point to point wires.



Regards,
Mike Willegal
 
I won!

I'm pretty shocked. I did a ton of research, talked to the seller about how these boards were found -- everything seems to point to them being legit. If they are, considering a Rev 0 Apple II board just sold recently for $1300 (and a later one with the dark green slots, no less), I gotta be pretty happy making off with these for $1500 and change! I thought I'd have to go to war against museums and so on. This leaves me with extra to pay for the ASR-33 I just bought. :)

I figure maybe it was a combination of things that held the price and competition down:

1) Hard to verify 100% they're real - maybe they aren't
2) They're bare boards
3) People probably weren't actively searching for them, given how rare they are, so they missed the auction?
4) People got psyched out by the anticipation of a bidding war
5) Maybe Mark-8s aren't as valuable as I assumed despite their rarity?

If they are legit, I'm very excited. This is the first truly ultra-rare thing I've gotten for my collection. I also have to hope the seller honors his end of it, I think he was expecting a much larger jackpot.

But assuming it goes through, and they are legit -- dare I build them? (once I get a h-ll of a lot more experience with other projects) I had a thought to just build a Mark-8 clone and display the real boards with them.

Ultimately these will end up in a museum, if I have my way. But not before I've enjoyed them a while first. :)
 
Congrats! You've certainly picked up some really cool stuff this year :)

You might consider sending these off to be scanned into Gerber files. I've worked with Mile High Test (now a division of Gardien) out of Colorado for scanning before, they do an excellent job and the service is prompt. Grant Stockley recommended them -- that's who he used for his Altair clone boards. You can specify no clean-up and they'll leave crooked traces and off-center holes alone. See my OSI 495 prototype board as an example:

http://www.glitchwrks.com/2016/04/22/cloning-the-495

If you want help with the project, let me know -- I'd be glad to lend a hand! Personally I went ahead and added a reference to my website in the copper layer on the OSI 495 boards, just so no one ever tries to pass one off as an original old board (there are plenty of other differences, but I figure the URL makes it obvious even to eBay buyers).

Gerbers can then be used to manufacture boards at a commercial board house (I know of a few suppliers who will give you an OK price on a board that large), or you can print transparencies/toner transfer and do boards at home.
 
Excellent!! Certainly went for less than I thought they would. Think you got a pretty good deal there.

I like Glitch's suggestion too. You could get a set of boards made up which you could use to build a machine and keep the originals in their untouched state. Of course, if you wanted to make several boards, I'd certainly buy a set :)

Cheers,
Dave
 
Thanks glitch! Yeah, it's been a pretty good year. I still want an Altair, but I might postpone that a while longer to absorb this (and preserve my marriage).

I'm curious though -- with the original artwork available (ie. via Bryan's site), why not just use that to reproduce boards, exactly as would have been in done in the day by those who declined to purchase them? I had some suggest to me doing something similar with my TVT boards, but I went with using the original artwork because to me that got closer to what the hobbyist would have done, and represented the actual work of the article's author. I'm a little nervous too about sending these away and risking them being lost. Doesn't happen very often but I tend to be lucky that way. :)

I've gotten a lot of conflicting advice re: build or not build. There is equal merit to both camps. The not build camp cites the rarity of the boards and the extreme rarity of finding unbuilt ones. They say worry about collector value. I kind of lean that way - thinking about how I cringed when that guy opened a brand new Atari 2600 box or that unopened Apple IIc. That's something you can't undo.

On the other hand, I recall an interview with a guy who owned a real Shelby Cobra and actually drove it. When asked why, he said 'what's the point of having it if you don't drive it?' Hmm. :)


glitch said:
Congrats! You've certainly picked up some really cool stuff this year :)

You might consider sending these off to be scanned into Gerber files. I've worked with Mile High Test (now a division of Gardien) out of Colorado for scanning before, they do an excellent job and the service is prompt. Grant Stockley recommended them -- that's who he used for his Altair clone boards. You can specify no clean-up and they'll leave crooked traces and off-center holes alone. See my OSI 495 prototype board as an example:

http://www.glitchwrks.com/2016/04/22/cloning-the-495

If you want help with the project, let me know -- I'd be glad to lend a hand! Personally I went ahead and added a reference to my website in the copper layer on the OSI 495 boards, just so no one ever tries to pass one off as an original old board (there are plenty of other differences, but I figure the URL makes it obvious even to eBay buyers).

Gerbers can then be used to manufacture boards at a commercial board house (I know of a few suppliers who will give you an OK price on a board that large), or you can print transparencies/toner transfer and do boards at home.
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