Layouts for for the five boards needed to build a SCELBI 8 H are near final. I’ve done all the design checking using my software as well as cross checking with schematics and I’ve sent gerber files to an online fab house design checker. I’m also getting quotes for pricing.

Just to give you an idea of how much work this has been, I’ve gone through the following approximate number of revisions of each board.

CPU – 81 revisions – this was the first board I started on, so some basic SCELBI things were figured out while doing the work for this board
DBB – 39 revisions
INPUT – 34 revisions
1KSRAM – 35 revisions
Front Panel – 16 revisions – most basic board, by far

The grand total number of layout revisions I’ve made since I started in earnest in October of 2011 is over 200.

I’ve also been working on the backplane, but it is not quite ready. The SCELBI 8H can be built without a backplane by hand wiring, and I’m likely to build my prototype initially that way, but getting a backplane made sooner rather than later, is not out of the question.

Here is a picture of Curtis’s hardwired 8H (image provided by Curtis)

Just a quick update on SCELBI progress…

I have completed schematic layout comparisons of three of the five main 8H boards. What this means, is that I have compared the layout to the schematics and corrected any unexplainable differences between the two. This is a time consuming process, but I did find a few mistakes in my layout, so this has been worthwhile. I also found (for the second time) that there is one small mistake in the DBB board schematic. I also discovered that there were two versions of the DBB board made (I am laying out the later version) The boards I have completed this check on, are the front panel board, the CPU board and the DBB board. The CPU and DBB boards are fairly complex and took a while to do.

The remaining boards, input and 1K memory, are less complex and shouldn’t take quite so long. After these two boards are checked, I have to do some checking of pads and hole dimensions for discrete components. I learned some time ago that getting hole sizes right is as critical as any other single part of this process. After the dimension checks are complete, I have a final CAD check left to do, before getting quotes and the boards sent off to be made.

I also have done some work on the 8H backplane. The backplane is starting to shape up, but I’m not sure if I will have these built along with the five main cards or not, since with a SCELBI you can hardwire a backplane.

I spent a couple of evenings taking another look at the SCOPEWRITER. Followers of my blog will remember that last spring, I declared the SCOPEWRITER project a failure. At that time I put it away, knowing that eventually I would make another attempt at getting it going. Well, I have good news, at this point, I can’t call it a failure, it might even be called a qualified success.

Here is an image of the output, that I was able to create.

Scopewriter

I had to make two changes from where I left off, in order to get this output.

So now I have a working SCOPEWRITER. Come the think about it, this may be the only working SCOPEWRITER in the world. What else will I do with it – well at some point it will make a fun output device for the SCELBI 8H and I may just have to create a web page for it. And one other thing – my point of view is that this is really a SCOPEWRITER, not a reproduction – I used instructions and PCB layout from the original magazine article to create it, just like a hobbyist would have done back in the 1970s.