Sinclair ZX80 / ZX81 / Z88 Forums

Awesome job Mark thank you for adding those, I will now treat all address lines on pinouts as A'n' and not a specific number, its greatly helped my understanding.

Ah thanks for the explanation Mark that might explain the discrepancies I'm seeing, my '81 has a '2016. Will triple check thanks

I've recently fitted a Murata switching reg (from retroleum) on my speccy works great, so I have literally just ordered one for my '81.

Shes only a 1k model no ram pack, I had a thought about RAM possibly being an issue so I did the 16k internal mod as it was a very cheap solution and the same result :'(
I've just ordered a new Z80 and a couple of transistors so I'll replace those which just leaves the ULA and ROM.

http://i.imgur.com/iCNqoDX.jpg Hope I've made my results clear, tried to colour code the errors to make it easier to look between chips, results were take with no tv or keyboard connected not sure if that will change anything. I notice HALT is high, so as that is linked to WAIT and NMI , via TR1 co...

I know I'm late to the party but I notice there is no pinout for a internal 16k 62256 28 pin chip or is that considered a mod? Also my '81 (Issue 3) has a 24 pin toshiba TMM2016AP-15 ram chip and the pin out doesn't match, I'm cross referencing a schematic drawn by Ron Reuter SRC 049 and the 2114s d...

Thanks for your reply Mark, unfortunatly I only have one zx81 so swapsies are out, I tested continuity on all pins all chips, and tested all pins with a logic prob, i'll post my results in the morning when ive written them up nicely, pin 6 on the cpu was high and pulsing (ph) so I dont think that is...

I've recently got hold of a nice clean Issue 3 ZX81, unfortunately I just got a white screen no cursor, I've recapped it, did a composite mod (transistor version), still getting a bright white screen no cursor, it has a sinclair labeled rom, a zilog z80 and a single 24 pin toshiba ram chip, I've not...