exxos's Atari, Amiga & retro forum

Well, inspired by @stephen_usher's Camputers Lynx II build, I think it's high time I started this build. I'm not 100% sure what I'm missing from the BoM, but luckily the PCB has a fantastic silk screen too which will help enormously.


More to follow :)

Well, reasonable amount done today:

Hopefully I'll crack on with this some more today, so hopefully more pics later, but I've at least managed to get some more parts on order.

The one difficulty is the CDP1861 video display controller, unobtanium seems to be not a strong enough word, however there seems to be a replacement here: CDP1861 replacement

It may well only be required for video output so I may be able to get things going with just the LED displays, but that's another story, as I may decide to go for the add on LED matrix board.

This is an interesting little machine, it may take some effort to get it going.

So, what is the Cosmac Elf II?

I think you need to join RCA (Retro Computing Anonymous) @rubber_jonnie you are a force majeure when it comes to building, repairing and collecting old tech. I do find reading your escapades interesting :)

stephen_usher wrote: 29 Mar 2026 18:37 So, what is the Cosmac Elf II?

Its a single board trainer type computer in a similar vein to the Science of Cambridge MK14 and the likes of the Kim 1 etc.

You can find more info here: Elf II

And what I'm building is here: ELF II Rev D

Icky wrote: 29 Mar 2026 19:37 I think you need to join RCA (Retro Computing Anonymous) @rubber_jonnie you are a force majeure when it comes to building, repairing and collecting old tech. I do find reading your escapades interesting :)

I'm glad I can provide you with something interesting to read :)

I have a soft spot for these trainers etc, despite never having owned one BITD, and I'm always on the lookout for similar things to build :)

It's not a bad count though so far:

1. OSI 600D Replica
2. SoC MK14 Replica
3. ZX80 replica
4. Acorn Atom replica
5. Cosmac Elf Replica
6. PDP 8 mini replica
7. Altair 8088 replica
8. Kenbak replica

Admittedly the last 3 are taking the 'replica' mantra to a bit of another level, but I can live with that.

I may try to build a video board for the MK14 I think, but I'll be sorting the Atom next with the Yarbb and AtomMMC boards, but I think I may look for another replica such as a KIM 1 or Heathkit Micro Professor if they are available.

I love what I do, can't help myself :)

More building has happened :)


So I'm now at the stage of looking at what's missing and getting it ordered. I'm not currently worried about the expansion sockets though.

More parts ordered, but in the meantime I've done a smoke test. 14ma shown at the bench PSU @8v. No smoke, no fire so looking positive. The power LED even comes on :).

Will need to go and raid my parts bin to see what I do have to hand, but going to wait until my decoupling caps arrive before I start plugging stuff in.

I have also fitted the keys, annoyingly I was a single Cherry Mx short so had to order that too. I'll need to print out some labels for the keycaps as none of them have the right letters on them.


:dizzy:

Progressing nicely:


That's all the jumpers done and the keys labelled. Once I get some more parts assembly can continue :)

Apologies if my slightly wonky labelling causes problems for those with OCD but it's the best my old shaky hands could muster!!!