Sinclair ZX80 / ZX81 / Z88 Forums

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 ...

Hi all, just in case you'd like to know: my ZX80 is ready and it's working. Does that make it serial# 3? The keyboard works without problems, I used schottky diodes instead of 1N4148 for the keyboard. There is a tiny problem with the display: Every displayed line begins with pixel line #2, followed ...

Hi all,
after a few hours of sleep I was able to read the schematics again.
Q1 is 2N3906 and Q2 is 2N3904.
So I will finish my soldering this evening and give it a try.

Paul

Sorry to bother you,
I nearly finished building my ZX80, but the list I have only mentioned Q1, and there was only one transistor in the kit.
The board requires Q1 and Q2, could anybody tell me what Q2 should be like?
Thanks in advance

Paul

They didn't arrive in Germany up to now
So there is nothing to tell from here.
@Lee: Do you want to share your advances in your documentation with us?

I'm looking forward to start.

Cheers
Paul