Sinclair ZX80 / ZX81 / Z88 Forums

Where will the devices be sold? Could you please announce it here, when there is new information.

Best regards

Any hints where to get one of these?

Best regards

The original ULA was DOA and has been replaced. Here is a pic of the bottom of the dead ULA. The top is glued to the heatsink forever.

[attachment=0]IMG_9383.jpeg[/attachment

Maybe i will go back to 16k mod. But my goal was to have 32k with WRX possible.
For today i will give up. Thanks for your advice.

Corrected to pF which i used. I have not used nF caps.

I checked my other mod and post a picture below. Here i us a 100 pF cap. The result is a correct display of WRX graphics.

Do you mean 100 nF is still to high, or over 300 nF. When I tried 10 - 100, always the same result / pic1.

I did a 16k mod on another machine with the same SRAM chip. Here the WRX hires works regular, so i thaught the problem would be the additional 32 k / 7400 part.

OR Pin 20 in the socket. Only a capacitor should connect to here. This pin must NOT be connected to 0V/GND. Pin 22 lifted and wired to pin 14 (which is 0V/GND). This is exactly my wiring. I tried some caps. Up to 100 pF ( nF ) i get the first result, 200 / 300 pF (nF) make second pic. Higher nFs ke...

Am i right Pin 22 lifted up -> GND
Pin 20 in socket -> GND

doenst work an results in this screen.

Maybe this can help. The schematic of the mod and an older picture showing the wiring. I tested putting the cap between the red marked pins. Here is a detailed description of the mod. http://www.8bit-homecomputermuseum.at/repair/zx81%2032k%20intern/zx81_32k_intern.html Normal progams, for example 3D...

ILAH wrote: ↑Fri Jun 16, 2023 5:32 pm I dont know, i think LC. I will report later.

-> I can not identify, the surface is scratched. Will the cap depend on the version?

The RAM is from Hynix:
HY62CT081ED-70C = 70ns refresh