Friday, October 14, 2016

RC2016/10 -- Halfway @ Half-time...

So it turns-out that walking through a wire-wrapping project isn't as thrilling as one might imagine. Hopefully the end of the project will enable new COSMAC adventures, but the steps along the way are mostly a 'lather, rinse, repeat' sort of process -- one wire after another, for dozens or hundreds of wires. But it has enabled me to build the paleotechnical skill of wire wrapping, allowed me to exercise my engineering sense to discover a mistake in the docs I was provided, and introduced me to some new friends on the Internet.

Some Progress
Building Skills

This project is my first time using wire wrap as a construction technique. While the process seems simple, it is not without its pitfalls. Cutting the wires to the proper length requires some expertise, as does proper placement of the wire in the wrapping tool, and proper use of the tool to minimize wire breakage. Good judgment about wire routing and proper use of wire colors also contributes to project success. I am reasonably pleased with the project so far, but I can only imagine that more practice will yield some improvements. As it stands, I am not completely convinced that this technique is in any way better than point-to-point construction with solder...

From PIN6 of IC1?
Finding Mistakes

The documentation included with my VCF ELF kit contained a wiring list for use while building the kit. This list includes each individual wire, grouped by circuit node. Each node's list reads something like "from A to B; from B to C; from C to D". As I reached the node for the /LOAD signal, I saw something more like "from A to B; from B to C; from D to E" -- notice the disconnect? That made me check the schematic, which made it clear that the wire list was wrong. But what is right?

The wire list showed the next to last wire as ending at "PIN6 of IC11", and the last wire as starting at "PIN6 of IC1" -- notice the similarity? Checking the schematic confirmed that starting the last wire at "PIN6 of IC11" makes sense, so I went with that. Later I found that there was an updated wire list at the VCF ELF website which confirmed my correction.

New Friends

For years I have been a member of the COSMAC ELF and 1802 Microcomputing Yahoo group. Until now, I have had little reason to actually interact with the individual members. I was curious about the RCA1802 and the COSMAC ELF, but I didn't have any hardware to use. Now I'm building this kit, so I made the members of that group aware of the project. So far they have been friendly and responsive, taking a healthy and welcome interest in my project. It's always good to make new friends!

More Progress
As I write this, the month of October is almost halfway over. That means half of the RC2016/10 event is over, and half still remains. Will I finish my build? Will it work at the end? If you want to find out, then I guess you will just have to stay tuned... :-)

1 comment:

  1. You will not see me wire wrapping anymore, these days it's actually easier to make a PCB.