I added some SCELBI comments from mid 70’s hobbyist magazines. Take a look.
I have a new version of the SCELBI/8008 OS/X emulator working that allows you to set the starting address after a reset, but I haven’t yet loaded it to the website. Hopefully I’ll get to that, this weekend.
In a previous post, I talked about how the lettering on the Apple 1 was probably done with a K&E Leroy system. However, I forgot to mention that the larger letters were not done with Leroy. Those letters were probably done with a Letraset or similar rub on transfer system. Take a close look at the Apple Computer 1 lettering, which is representative of the larger lettering seen throughout the board.
Apple1logo
This lettering is in the general form of Helvetica, with subtle differences from most variations of Helvetica that you see today. Through extensive searching I found a very close match with Neue Haas Grotest Std Text 65 Medium. This is a recreated version of the predecessor to Helvetica. Check out this page with more information about this font.
Here is a recreation of the Apple Computer 1 lettering using this font. I think it would be hard to beat this match.
Replicated Apple Computer 1 logo
replicated Apple 1 copyright notice
If someone has a Letraset catalog from the 70’s, it would be interesting to see if they can find a good match in one of those catalogs.
I recently received an email that indicated that the Apple 1 was most likely lettered with the Leroy lettering. That email has resulted in a lot of research and exploration of exactly what is Leroy lettering and was it really used for lettering the Apple 1 PCB.
First thing to figure out is what is the Leroy lettering system? It is a system to mechanically create lettering that was intended to generate legible lettering on a drafting table. Engineering documents, maps, architectural drawings and the like were the primary applications.
Here is an image of a K&E Leroy lettering set.
K&E Leroy Lettering Set
It’s easier to show how it works, than describe it. Here is an image of one set up to make a capital M. The scribe follows the letting in the ruler like jig and ink in the “pen” writes a pretty exact copy of that letter. There are a series of jigs for different sized letters. The scribe tool can be adjust to make the letters slanted in an italic type fashion.
Leroy Letterng Sytems Set Up
So how do we determine whether this system was used to make the lettering for the Apple 1. The easiest way is to compare the lettering on an actual Apple 1 with an example we know was made with Leroy lettering System.
Apple1 Leroy Lettering compared to Apple 1
You can see that the newly created Leroy lettering (bottom) is nearly a perfect match to the Apple 1 (top), so I think that we can be pretty confident that the Apple 1 lettering was made with the Leroy or very similar lettering system.
My next question is whether the SCELBI front bezel was also lettered with the Leroy system.
Leroy and SCELBI Front Panel
Though the lettering is very close, there are some differences in the leg on the “R” and the “A” looks a little different. Also the ends of the strokes on the letters have nice square edges, which would not occur in a Leroy lettered system.
Finally, follow this link to see what Wonder Woman comic books have in common with the Apple 1.
I have the layout for a reproduction SCELBI TTY PCB close to complete. This is essentially a TTL to current loop interface originally designed for interfacing the SCELBI to a Teletype. The board is about 4.5″ x 3.5″ with a connector on a .156 spaced edge for plugging into to an edge connector with solder tail pins. This is very similar to a “Vector” prototyping board. Schematics and a drawing are available on Cam’s SCELBI website.
http://www.scelbi.com/documentation.html
Here is a photo of an original SCELBI TTY interface board.
SCELBI TTY interface
I’m not sure how many to make. I’m projecting a bare PCB price at $30 to $40, depending upon interest level. Let me know if you have interest in this board.
regards,
Mike W.
In this series of earlier posts and I had posted some notes on acquisition and repair of an all original MAC 128k. One thing I didn’t mention is that the video on the machine was a bit intermittent. This has bugged me a bit and yesterday, I decided to figure out what was going on. The symptoms were intermittent video, either working normally, or completely black. Taking the machine apart, I determined that wiggling or touching the connector that leads from the digital to analog board could cause the video to go on or off.
Some websites and an old book, “Macintosh Upgrade and Repair Secrets”, say that this sort of problem is often due to bad solder joints on the connectors on the analog board. Following those directions, I pealed off the plastic cover and resoldered the joints on the analog board. However, this did not affect operation. Figuring that I had nothing to lose, I then touched up the joints on the connector on the digital board. Wiggling this connecter seemed to affect the problem, so I was kind of hopeful that resoldering that connector would do the trick. Sure enough, the intermittent operation seems to have disappeared once I resoldered those joints. Now, I just need to find some foam with adhesive on both sides to use, to put the plastic panel back over the analog board and I think I’ll be back in business.
I hope I don’t have any further issues, at least for a while. By the way, my opinion is that those connectors could have used a bit more solder in the first place, and this probably contributed to the issues.
This experience with a MAC 128k shows how even a lightly used old computer that is in excellent cosmetic condition, may need some work in order to get it running like it was new. I had three problems with this machine that needed addressing.
Note that there are high voltages in this system and it should only be operated by experienced technicians when the cover is removed.
I figured I would report on my SCELBI exhibit operations at VCF SE 1.0. I will also cross post this to the new yahoo group, retro-restore.
Saturday was dedicated to running the SCELBI calculator program. Toggling in the bootloader before exhibit opening, went without major issues, though I found that focus on toggling was a little hard to keep with numerous other people around getting the facility ready and getting their exhibits ready. No significant problems with downloading and pretty soon I had the program running.
I had left the divide by zero error handler to just halt the CPU. This turned out to be a good way to demonstrate front panel operations, as I just needed to divide by zero in order to halt the cpu. I would then need to toggle in a jump instruction in order to get the program running again. I did have a few issues during the day when the program appeared to stop accepting input. I think the main reason for this, is that the parser is rather particular, expecting only certain characters during input at any given time. Other characters are ignored, making it seem like the program or machine is stuck, when, in fact, the operator is typing the wrong thing. Anyway, the program ran all day, without any need to reload it, until I took it down to demonstrate during my talk.
The second day, I was planning on demonstrating Mark Arnold’s 1K Mandelbrot program. I arrived just 20 minutes before exhibit opening and because I was also demonstrating a Mimeo and had to set that up, and didn’t have time to toggle in the bootloader before opening. I had to do it, while showing off my exhibit. The Mandlebrot program needs to use location zero, so I had to relocate the bootloader. Last time, I did this, I had no issues, but this time my math skills failed me and I spent a considerable amount of time trying to make the Mandlebrot program load right on top of the bootloader. Finally after realizing the error of my ways, I retoggled the bootloader into a better spot and got the Mandlebrot program loaded and running.
If I had been thinking straight, I could have loaded the bootloader into the new location, with the bootloader that was loaded in the wrong place. The SCELBIgenerated Mandlebrot images for the rest of the day, without error.
The bottom line is that the SCELBI ran all weekend, the clock remained stable enough to support RS232 bit-banged I/O without error. The power supply worked great.
A lot of people that had never heard of it, were exposed to the SCELBI for the first time. And finally, I overheard one person say that the reproduction SCELBI was the coolest thing at the show.
Things I would change. I would probably run the Mandlebrot on Saturday, when things were busiest. I also need to find a teletype or current loop terminal,because some people were confused by the Powerbook running a terminal program acting as the terminal.
It was wonderful meeting everyone who came to the show and if you didn’t come I recommend you make an effort to attend a VCF, if you get a chance.
As I noted in a previous post, clock stability on my reproduction SCELBI was pretty bad. The system clock slowed down 10 or 15 percent as the system warmed up. This would have played havoc with my bit banged serial communications, but by the time I was able to toggle in the loader, it would be warmed up and fairly stable.
SCELBI cpu clocks
The timing circuit is made up of 4 interconnected 74121s one shots that control rising and falling edges of 2 interleaved clocks. The timing of each 74121 is controlled by a 5K trimmer resistor and a 300 pF cap. Figuring that the cap was part of the problem, I looked for some NP0 300 pf caps to replace the ones that i was using.
What I found was a modern 330 pF cap, Kemet part # C322C331J2G5TA. While I was at it, I decided to replace the 5K trimmers that I had been using since first bringing up the SCELBI. The original trimmers I bought had the wrong foot print and turned out to be a little jumpy while adjusting. I replaced them with Bournes # 3006P-1-502LF.
Though I don’t know which change made the difference, several trials have shown the new trimmers and NP0 caps seem to have stabilized the clock to the point, where I think I can forget about the “problem”.
The only thing I might do at some point, is try to find some old style NP0 caps to replace the obviously modern Kemet ones.
Check it out. John Calende is documenting his reproduction SCELBI build in a new blog.
blog:http://myscelbi.blogspot.com
I have permission from Wendell Sander to publish a high res scan of an original print of an Apple 1. We believe that this is either the exact image used in the original ad or at least from the same photo shoot. We are so lucky that Wendell saved this very detailed print all these years, and is so willing to share it with all of us. I have updated the flyer and included this scan, which pretty much makes this reproduction about as good as I can make it, at least in available time. I left the image uncompressed, in case you want to blow it up to poster size.
enjoy…
It appears that Rich Dreher have made another batch of CFFA 1’s available.
http://dreher.net/print.php?s=projects/CFforApple1
I have tested these in the Mimeo and they work great. If you are tired of dealing with the cassette interface or a serial port (on PS/2 adapter), these are great way to load programs into your Mimeo.
The CFFA 1 also adds in extra memory, so you can run the some of the larger Apple 1 programs that are available from Wendell Sanders web site.
Do note, that in order to preload the compact flash with Apple 1 software on a PC, I think you need to use a Windows program called Ciderpress. I don’t know of a Macintosh equivalent. You can always load the program on the Apple 1, using my PS/2 adapter’s serial port, and then save to the CFFA 1. CFFA 1’s use the Apple 1’s slot, so unless you have a slot expander, you can’t use both an ACI and CFFA 1.