Sinclair ZX80 / ZX81 Forums

But YannFr should be first in the line, as it's his topic. I'll have it though if he doesn't want it.

I thought that you'd found details of a very similar device online somewhere, not that you'd created the circuit details! I'll open it up again and will let you know about the resistor and cap values.

I am, but I suspect I'm not the only one.

Shame US only, as I'd certainly have those (perhaps without the printer as a bit bulky and faulty). I suspect the shipping is a fortune though, but I'd certainly offer US$80 with shipping to Germany, if that's any good?

Excellent, it certainly looks exactly like that (without checking each connection yet). I'll feed it with 5v and a cassette and see if it makes any difference.

I'm following this more intently now, to see how you get on with yours. I was inspired to get mine to a working state, so popped the chips on, added a power socket and with ZX8-CCB Video, plus a 2732 ROM with the correct data on it, all I get is a plain white screen (a little flicker, then white)! I...

I have a Chinese EPROM programmer and before I started putting the sockets/resistors/caps etc on the board I thought I should probably check all the chips as their age and source was unknown (I wasn't bothered about the Z80 as I have some known good spares of those). I was able to use the same progr...

I bet the EPROM is empty for a start! With mine I also got a couple of wrong 74XX chips, so also check those are all correct.

Oh yes, I have those alternate EPROM connections on mine too, never noticed that! Well, in that case, that looks ok.

Here we are. Back is marked with the transistor positions (both are BC239C) and C for capacitor, R for resistor.

Any idea why the circuit is broken where those two wires come out next to that resistor at the bottom?

Yes of course. I would have removed it all, but it looks like I'll have to remove the switches and 5v socket to get the board out. The CR-TB switch just choses between 2 different resistors and neither position seems to make contact so I'll take everything out and clean it all up.