cause I have now a working manual wired circuitry I have now designed a PCB.
Here some 3D previews:
The pcb can be placed in the socket of the original Lambda ROM. The for pins on the left side may be connected with reset and three keyboard lines. Alternatively the use of switches is possible either.
I'll now check the PCB on paper and if it is OK I will start a sample production of 4 pieces.
Is this something I should be jumping on? What are the advantages over a ZX81? I see: Better keyboard, monitor out, joystick port. Downsides I see: No tokenized verbiage, incompatible character set, programs?, more junk the wife doesn't understand the romance for,...
The multi-ROM sounds cool, but do I want to start a fresh trip down this road? I don't know if I'm asking for someone to talk me out of it, or into it, lol.
for me it is difficult to give you an advice if you should by the same.
30$ is in my opinion OK, if the machine is in a good condition and maybe equiped with a 16K Ram expansion.
Here in Europe I bought the same for 20€, but with some scratches and holes on the case.
The Lambda will never be 100% compatible with the ZX81, either if some modified ROMs are used. Non-Hires SW will work with the modified ZX81 ROM.
With the Lambda ROM, only basic programs will be compatible.Either there are not many SW titles available for this computer nor tools. Thats one of the reasons for the Multirom.
Another differences, the expansion bus has some signals missing, so a zxpand cannot be used, the display is inversed (white on black background).
On the other hand hte lambda is a rare machine, which is placed somewhere between the ZX81 and the Speccy. It has a speccy like keyboard and sound and a joystick connector. With a color module it can do color either (i have not tried, but thats another reason for this project, there is a color rom available).
For me it is a cool computer cause I can use many ZX81 SW titles, the machine is rare and in some way strange. However it cannot substitute for me an original ZX81, it is just a add on.
I hope i could have helped you with those statements.
Thank-you very much for taking the time to give me the benefit of your input.
The unit is apparently cosmetically quite good, with all manuals and cords included, (even a tape recorder thrown in), but without any RAM expansion. I imagine one of my Timex-Sinclair packs would work on it? I have orphan ZX81 ROM(s) from scrapped machines, so I can see where this machine could be fun to experiment with.
The $30 is no barrier. Three hours of driving is what I have to decide on. I like the idea of owning a fine example of a rare machine. On the other hand, that might be crossing the line from being merely a Romantic ZX81 Geek, to Vintage Computer Collector. (Shudder!) Which of my wife's clothes would I throw out to make room? How will I explain myself in couples therapy? Decisions, decisions,...
Anyway, thanks again, and good luck with your project!
maybe the seller can send the computer via UPS or some other postal service, so you save the 3h driving?
Your wife does not understand you? My wife does not understand me too! For her my old computers (I have got 50 or so...) are just hazardous and stinking electronic waste. Anyway, some of her hobbies I myself cannot understand ....
I think your desire is to own that Lambda, so if I would be in your position, I would buy!!!!!!!!!!!!!
(If you only want to play with ROMS, the Multirom will work with a ZX81 too, despite it is designed for the Lambda. And just to emphasis, the Lambda won't work with unmodified ZX81 ROMs. )
When I tried to use a 16k memory expansion from ZX81 with the Lambda, it got defect. Maybe it was a case of random, maybe it was one of the very first 16k packs from sinclair, which was critical to some signals .... I dunno.
Maybe some other persons here or in the german forum may have better knowledge about this issue .....
You read my mind--I actually did contact the seller and we agreed on an arrangement for him to mail the computer to me. So, yes,... I'm weak,.. and I bought it.
Thanks for the info about the RAM pack not working. I'll try a Timex 1016 and see what results I get. It it doesn't work, maybe I'll look into adapting the ZX-TEAM "32K modification" for this computer. That would be a fun challenge for me. The documentation is promised to include a service manual, so I think I might be able to manage it. (Designing circuit boards and writing ROMs is a little above my weight class though!)
I'll stay tuned with great interest regarding your multiROM.
here now the final version. I will order two protoype PCBs this week. To keep prices low it will be delivered within 3 weeks, so before the ZX TEAM meeting in Germany I could perhaps finish one and test.
The RAM pack is a Timex 1016 and works fine. So would a printer, apparently. The computer has inverse video, and is apparently very clear on a modern TV with its composite out. The keyboard optionally beeps, and does not do 1-key BASIC terms. Trying samples from my ZX81 tape library, it seems content with Sinclair BASIC but not machine code designed for the ZX81, nor does it seem to conserve the value of variables that have been set into a tape image. Well darn.
My wife saw it and didn't say a word. She must think its another Sinclair, and doesn't know I just bought it. Shhhh,....