Who knew such a little computer could be such a big pain 🙄
Well RAM is ruled out. I think I am dealing with a bad ROM. D3 off the ROM seems to have lots of 0's. Also I am told there are HALT instructions in the rom code but the /HALT pin never drops on the Z80. What ever code it is executing sure doesn't seem right. Sockets installed. Ordered a 2364 to 27c64 EPROM adapter from RETRO Innovations. Now to wait for the mailman 😴
Well I got a EPROM burner and rigged it work on the 2364 rom I pulled. I see 8 bytes that don't match the ROM images I find on the internet. I put my read image in an emulator and it never boots. The live memory map shows it stuck in a bootloop at about the same rhythm I am seeing on the scope. I think I am on the right path 🤞
Well I got some 27c64's.. it at least does /something/ now 😆
@junkman All computers are a pain. That challenge is what makes them so fun. 😀
If you have to replace any IC, socket it.
@publius Ya thats the plan. The ZX81/TS1000 boards are not the most study things so I want to minimize the amount of times the iron touches it.
It verily appears to me that you're outputting with the horizontal & vertical transposed!
@junkman folks who had them in the early 80's? (:
(Still have mine, just, not here. Need to get it here.)
Seriously, though, getting a proper keyboard for this was ... pretty much impossible; yes Memotech made one, but it wasn't readily available and cost more than the machine, tv, and tape recorder (which is what I had money for.) My dad bought a keyboard for me - which came from some mainframe or something - and while it had keys, it had no... I couldn't solder and it just... yeah. He was rather upset that he'd not been able to help, as he knew I really wanted a proper keyboard -membranes are just crap...
But, well, I did do a lot with it despite it being such a pain (:
@Truck Ya I thought the CoCo1 "chiclet" keyboard was bad. The ZX81 one is next level 😆
You could always get/make one of these http://www.zx81keyboardadventure.com/2019/05/zx-key-external-keyboard-for-zx81s-and.html
@junkman I could now; and likely will; but back in 1985 that wasn't an option (:
@junkman ❤️ I loved my old TS1K. So many hours spent loading programs from tape and arduously keying in new ones on that membrane keyboard. Dad thought I was nerding out too hard so he put a literal axe through mine. Good to see at least one has survived this long!
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