Thanks to Mark Arnold, who stripped down SCELBAL to the barest fundamental elements, I now have BASIC running on a 4K SCELBI 8H for the first time, ever. Mark, who created SCELBAL back in the mid 70’s calls his new stripped down version of BASIC, “tiny SCELBAL”. He removed all non-essential features, including support for floating point math in order to make it fit into 4K. There are only about 350 bytes for program space left in a 4K SCELBI 8H, but that is enough for some very simple games. I have ported a version of HILO from Ahl’s “BASIC COMPUTER GAMES” book, and made it fit. I’ll be making a video, posting source and object files very soon. I’ll also post the source of HILO and describe some space saving tricks.

Mark says SCELBI considered doing this back in the 70’s, but determined the result would be too limited to be useful for most practical purposes.

I hope to announce within a few days that a SCELBI 8H has done something that a SCELBI 8H has never done before…

This is something that was possible back in the heyday of the SCELBI mini-computer, so no, I’m not connecting a SCELBI 8H to the internet.

I’m now taking orders for custom made reproduction SCELBI 8H front panels.

Price is $65 plus $10 shipping continental USA or $20 international. I am pricing these more as service to SCELBI PCB kit builders than for profit. When I eventually sell most of the 20 that I have made, there may be a small profit in it for me, but it will not be much. Based on my experience, unless you were already set up for making custom front panels, making a single one for yourself would cost at least two to three hundred dollars.

A couple of things to be aware of.

Send an email to:mike@willegal.net if you need more details on ordering.

We are almost there.

SCELBI Front Panels

I need to reprint the bottom portion of a few that I printed last week. This weeks session went much better. There are a few minor defects in the printing, so I’m not guaranteeing perfection.

The printing is pretty fragile. IPA takes it right off, with almost no effort. I’m going to experiment this weekend with spraying a light coat of clear as a protective overcoat before taking orders.

Regards,
Mike W.

I found a digicam and was able to take these photos.

SCELBI Front Panel Natural Lighting

Front Panel – flash lighting

This panel has more scratches than most of them. Installed and in normal lighting it takes close inspection to reveal them. It is good enough that I’m going to use this panel on my “exhibition” SCELBI.

Within the next week, I should be able to screen print the rest of the panels, figure out the best way to ship, and set a price.

Unfortunately I can’t find a decent camera, so this is a poor iPad shot. There are some small defects and a bit unevenness in the printing, but the overall appearance is good. I think I can improve the unevenness by using more “ink” during the “production” run.

Trial Front Panel

Front Panel II

I have a jig made, so I can print the rest once I properly mount this trial unit and do a bit of checking on the how well the paint adheres to the anodized aluminum.

Compare to some of the images at www.scelbi.com

I just added the correct SCELBI power connector to my reproduction. Note that this was the factory setup. Back in the day, some people integrated power supplies right into the chassis, rather than using an external power supply. The plug is a 86CP4 and the socket is a 78S4. These days, they are kind of scarce. In this case, scarcity equates to price, as they are about 9 dollars each. Check inventory at alliedelec.com for 78S4 and at tedss.com for 86CP4.

Here are some images.

SCELBI Power External

You put the plug in the chassis so the cable coming from the power supply doesn’t have exposed pins.

Inside Power Wiring

The SCELBI manual says put +5 on pin 1, ground on pins 2 & 3, and -9 on pin 4. SCELI assembly directions have you position 1 and 4 at the top of the chassis. This makes wiring to the backplane pretty clean. The slip rings that are used to hold these connectors onto the panel are a pain to get on – be patient and don’t expect the rings to seat perfectly. I chose to connect the I/O port grounds directly to the incoming ground wire, rather than wire back to the backplane. Now I’m thinking I should have run both ground wires to the backplane, rather than join them together and run 1 wire to the backplane. I used 18 gauge wire, so it probably doesn’t matter.

Plugged In

The socket and plugs are keyed, in that two of the pins (positions 1 and 4) are larger than the other two. However, I think if you weren’t paying attention, you could plug this in far enough to make contact and cause problems. Be careful when plugging this unit in.

I have used electrical tape to protect the exposed terminals on the cable coming from the power supply. I need to pick up some of the hoods that are designed to cover these connectors. SCLEBI used gray clad multi-conductor cabling back in the day. I think it is still available, but like many SCELBI components, it is pretty expensive.

This process took me a couple of hours. Take your time to get things right and avoid costly mistakes.

Next up – getting the TTY interface built up and checked out. Other than schematics, and parts placement, we don’t have documentation for that board, so it might take a while.

7/7 is the 40th Anniversary of Nat Wadsworth running the first program on the first SCELBI. Thanks to Mark Arnold for reminding me of this.

Regards,
Mike Willegal