Sinclair ZX80 / ZX81 / Z88 Forums

Happy 2021,

Where are you based?

Hi, Are able to solder missing components? Do you have any experience with reading circuit diagrams? Do you have basic tools like a multimeter? If you need any documentation you can contact @superfo, and he is registered on this forum. Don designed this board and he will be able to give you a hand. ...

1. 5 but if ULA is 5C112 or later type + 1. 3. 8x5 4. ZX Spectrum 128K +2 (with Issue 3 motherboard) 5. Combined Cycle Gas Turbine 7. ZX81 Issue 2 does not exist in the wild 8. ACIS chips in Enterprise 128K 10. 1.4A @ 9Vdc = 12.6W 11. Light-Emitting Diode ; blue LED Vf is in range between 2.5V to 3....

Nice upgrade.

Four brand new and fresh demos for Zeddy presented last night: https://www.youtube.com/playlist?list=P ... v6o0LV46a7

.p files will available for download at https://www.pouet.net soon.

Have a look around 40077 chip (ULA). I would not be surprised if some of soldering joints are cracked. It might be a good idea to re-flow the chip.

Thanks for info, but postage limited to Germany only.

Hi Andy,

It is a very good idea I've got a silly question. All buffered lines have pull-ups. Do you want to keep them HIGH when they are nor used? In my understanding they should be LOW if they are not used/active.

I have never tried to load any WAV files, only TAPs from JAA websites. If you have TZXduino I could share a few files that works and you try with them.

Bear in mind that Jupiter ACE TZX files should be converted to ZX Spectrum timings if you would like to use a bulk standard TZXduino firmware.

Pin 13 of Z14 is directly connected to the data line D5 and you can see all data flowing there. Take pin 13 of Z14 out of the socket and then see what you have there during the LOAD execution. If you would like to separate LOAD signal only, the oscilloscope should be triggered by the 0xFE read pulses.