Sinclair ZX80 / ZX81 / Z88 Forums

Thank you for the valuable input. Like an excited puppy, I guess I rushed into the building process without pausing to reflect and think. I'm learning a lot though and having fun.

There is life! Poking, prodding and a new CPU later. I suspect a via wasn't plated properly. I'm going to re-solder as many of the vias as possible. I can certainly testify to the fact that the ZX80 does NOT like an HC chip in the U9 position. If it is not an LS, it won't work. Also, tapping around ...

I'm using as many LS chips as possible. Some I could only get in regular 74, like the 7405s at U15 and U14. I'm testing with a NEC D780C-1 borrowed from a ZX81. U13 had to be a 74HCT04N and one 74HCTLS74 at U18. The weird thing is that it worked for two weeks, and then suddenly died. I'm getting a n...

I recently built a ZX80 replica and it worked great. http://www.myprius.co.za/ZX80kit/zx80_cir.gif Unfortunately, it failed recently. It only produced a blank raster and on the oscilloscope, the video signal timebase would vary wildly. Here is what I've tried so far: - replaced 7805 - replaced every...

Thank you. I really appreciate the help.

Can someone suggest a joystick interface for the zx80 that is Kempston compatible? I have a ZX80 replica I built from a kit and it works great. I made a small game controller with pushbuttons and soldered it to the cursor keys. It worked but wasn't particularly elegant. The wires also picked up RF n...

I had great success with the 555 based back porch generator from: http://zx.zigg.net/misc-projects/ It works very well. Granted it is a bit more complicated, but if you add an external power source you won't have to open your ZX80 up at all. Here it is working on my ZX80: http://www.myprius.co.za/ZX...