Sinclair ZX80 / ZX81 / Z88 Forums

1024MAK wrote: ↑Mon Feb 15, 2021 11:35 pm Here is a simple circuit that will detect when you programmer is trying to program an EPROM, the circuit then switches a 27V battery supply to the programming pin.


Mark

Nice, thanks, but I assume because I'm only going to use the 27v for these EPROMs, that a simple switch would be OK?

That's cool

I would say then the programming voltage isn't up to par. where does this programmer get its supply voltage from and is it possible to use an external programming supply? If so three 9v batteries wired in series I find is more than adequate when I program EPROMs with no programming failures yet apa...

I don't think I have a 30v PSU, but what do you think to this? https://www.youtube.com/watch?v=F9ADB7ImSwc

1024MAK wrote: ↑Mon Feb 15, 2021 1:54 pm

Do your ‘failed’ EPROMs verify in the programmer?

Mark

Yes, they read OK, all FF's

I bought 5x TMS2532A but only 2 would program.

Is there a better option? I have a TL866CS programmer and made an adaptor for these TMS2532A.

Thanks, I'll hang on to them then, try them in another machine.

Thanks for that information, I'm sure I will have to repair others in the future. I don't think the RAM was the original fault, but I had swapped the RAM to see if that was the issue. I think removing the muck from the rear of the board fixed the main problem. I had 10x 2114 RAM chips, it turns out ...

WOW WOW WOW! It's working!!! I swapped out the RAM and it didn't help so I tried other things and then swapped the RAM again and it still didn't help, BUT on the third swap I get a fantastic little cursor with a 'K' in it :D It's currently typing N's all over the screen, but that's probably some wet...

OK, I don't think the intermittent SYNC is a bad connection, it just seems that sometimes when I connect power the SYNC is there with black vertical bars, and sometimes nothing.