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falter
June 20th, 2017, 01:02 PM
I have just about finished my TVT and am looking towards my next project. In the short term that'll be the clone of the Sol prototype I'm working on. However the artwork for that is very messy and it will take months to clean it up enough to be useable. The Mark-8 project is in park until I decide whether I want to use the original boards or not, and in the interim it'll take a few years to acquire the correct year parts.

So I was thinking about making a SCELBI to go alongside my Mark-8. And I'd like to make my own boards from scratch rather than buy kit boards.

I realize not having access to original boards and given my limitations with schematics that this will be an enormous task. And I was going to buy Mike Willegal's kit boards at one point. However, finding this cache of vintage 1973 board stock has made the prospect of doing my own a bit too irresistible. I don't like the look of modern PCB substrate for vintage projects. With what I have, I've even thought about ripping apart my TVT and redoing it. It just brings the authenticity that much closer, although my skills at making PCBs will limit the quality.

Am I correct in my understanding that there is no artwork out there for SCELBI because it was offered commercially? I've got pictures of original boards - I was thinking I could use those as a background and trace them with Photoshop. I'm wondering also if there are any copyright issues with SCELBI stuff. I will absolutely not do anything illegal or steal designs from anyone else (esp. Mike), and I'm not interested in trying to produce copies for others. This is totally going to be a one-off to take advantage of this vintage board stock I have.

mwillegal
June 23rd, 2017, 09:57 AM
No original SCELBI PCB artwork exists, at least that I know of. On the positive side, the schematics are mostly accurate. One thing to be aware of, is that unlike the Mark 8, the SCELBI boards had plated through holes, so making your own boards has that significant complication that you will have to find a way to deal with.
Keep us informed on your progress.

regards,
Mike Willegal

falter
June 23rd, 2017, 07:43 PM
No original SCELBI PCB artwork exists, at least that I know of. On the positive side, the schematics are mostly accurate. One thing to be aware of, is that unlike the Mark 8, the SCELBI boards had plated through holes, so making your own boards has that significant complication that you will have to find a way to deal with.
Keep us informed on your progress.

regards,
Mike Willegal

Thanks for the encouragement. I think this is probably beyond my skill level but I'm eager to try. It will not be as professional looking as the originals or yours, but I'm hoping the use of original vintage PCB stock will help matters a little. Further I'm hoping if nothing else I get better at reading and understanding schematics, which would be useful elsewhere.

I've found several places where scans of original SCELBI boards are present like here: http://www.scelbi.com/images/cards/frontpanel-front.jpg I figure these are useful as a rough guide - they appear to be dimensionally correct. Obviously the IC's obscure some traces but that's where the schematic reading I hope will help.

I'm going to try the front panel board first, since it appears to be the least complicated and kind of go from there.

Roland Huisman
June 24th, 2017, 02:06 AM
Making via's can be done... You have to drill the board before etching...
https://www.youtube.com/watch?v=KTNuTv_IQp4

I've put away all my PCB making and etching stuff years ago.
I don't want to have those chemicals in my home any more...
The board quality from the Chinese manufacturers is just fine.
You cane make them without any green mask or text layers as well...

http://www.vcfed.org/forum/showthread.php?54312-Dec-H851-pcb-redesign&p=442189#post442189

falter
June 24th, 2017, 07:50 AM
Yes I was looking at that video. It looks.. involved
:)

I was wondering though.. can I not just employ the same strategy as with the Mark-8 boards to connect sides (ie via wire, etc). It won't look 100% correct of course..

Chuck(G)
June 24th, 2017, 08:52 AM
Tiny copper rivets for vias are inexpensive. They're entirely period-correct if you don't want to go through the hazard of plating your own vias.

livewire
June 25th, 2017, 03:47 PM
If'n you really want it to look original, you're gonna need a fist full of these little bits of unobtanium from 197339301. :cool:

falter
June 29th, 2017, 01:58 PM
Are those what are on this one? They look different for some reason.

http://www.scelbi.com/images/cards/frontpanel-front.jpg

Chuck(G)
June 29th, 2017, 03:41 PM
If'n you really want it to look original, you're gonna need a fist full of these little bits of unobtanium from 197339301. :cool:

Hmmm, the ones that I bought from Monsanto in 1969 were all epoxy. I may even still have one. Miserably dim, in comparison to today's ones, however.

falter
June 29th, 2017, 06:09 PM
This original SCELBI doesn't appear to use those:

http://bugbookmuseum.blogspot.ca/2013/03/vintage-computer-scelbi-8b.html

Chuck(G)
June 29th, 2017, 07:52 PM
Those look right for the early 70s. Compare, for example, the LEDs on even the very first Altair 8800s. Same stuff. The great thing is that you can still get red LEDs in the same package in modern manufacture. Much, much brighter--and probably much longer-lived.

livewire
June 30th, 2017, 08:19 PM
I believe that these three are original SCELBI builds. And yes the other LED designs existed back then. I have many blinky Altairs and their ilk to prove it.
It's just that these are the most rare. (and not bright at all)394253942639427

Corey986
July 3rd, 2017, 03:26 PM
The earlier 8h seemed to have the metal cans. The 8b pictures I have seen have the more modern looking LEDs which was a little later on, but still preparing the ALTAIR. The one from the bug museum must have been a later build.

mwillegal
July 5th, 2017, 12:10 PM
Keep in mind that SCELBIs were sold as completed units, kits, and PCBs, without components. With SCELBI's, basically anything that might have been available back in the mid 70's, could be considered "period correct".

regards,
Mike Willegal