Sinclair ZX80 / ZX81 / Z88 Forums

FANTASTIC!!!

My Pension Day will be somewhere around ZX80's fiftyth Birthday
so I do hope to get one a few days before that
I was lucky to get a test board from Lee,
Charlie, please take me as a testuser, too
Paul

Thanks a lot charlie,

can't wait for the moment when I hold one in my hands!

Please post photos of the empty and soldered board too!

Cheers Paul

hi all, there is a way to get a ZX80 ROM running without problem without the need of cutting the NMI line. It is taken from the german ZX-Team forum, where it was posted recently by the original user holmatic: http://forum.tlienhard.com/phpBB3/viewtopic.php?f=2&t=412 The first instruction in a ZX81 ...

After his last visit, Jens found out that every line is shifted by one "Subrow" upwards with Jumper 5-6 set. You can see this quite good using the shift-S Character as all lines are used there It is the same with my board, with ZX80 and ZX81 rom. Is this the same on the other boards? @Lee, has this ...

Yes, correct no connection to the pad of R30. Thanks for the description, this explains why nothing happened to the signal level: R32 is exactly in the middle position, I forgot to try to change its setting :oops:, or even to compare their settings, because there is absolutely no problem with my mon...

Hi Lee, I also misinterpreted the photo. Luckily I could see #4 in live. The yellow wire connects the additional diode directly from R37 to D13, no connection to R31. I hope that makes it clear. Why my modification from 1K to 500 Ohm did not increase the video level I cannot tell. I checked the valu...

Neither good nor bad. At the moment 4 out of 5 Boards are completely built. One does not work (Jens), it gives no signal to the screen, there will be further investigation this weekend. Two work with the known error of the keyboard. SirMorris replaced the diodes with no effect. My board still works ...

I made a EEPROM with ZX81 + ZX80 + ZX80 ROM inside and tried out a bit. The printing near w5 doesn't seem to match the schematics. There is 5V at '27128' where should be A13, and A13 at '2732' where should be 5V. The schematic also states 2716 here, where it should read 2732 like on the board. This ...

Hi SirMorris, I'm using BAT41. It took me a quarter of an hour to find this out. I had to use the power of two magnifying glasses :oops: It is 100V 100mA. The voltage drop of mine were between 291mV and 316mV. The datasheet lists them with 0.4V But I didn't select them. I just went to my local elect...

Thanks for your reply, Lee. Yes, the keyboard works with all shifted keys as well. So the diode drop was the problem (or my configuration works for any other reason). We will know for shure if superfoe or SirMorris replaces the diodes and this solves their problem. No, there was no jumper installed ...