Glad to hear it!!

According to this site D1 is U9 not U12??

https://myoldcomputer.nl/technical-info ... 5-01-c64b/

I am assuming that you have swapped the ram chips around to see if the error follows either u12 or u23 and have checked for data bus shorts to ground with a multimeter? The results you are getting would indicate to me either a ground short on D4 ( u23 data ) or more likely a short between D1 and D4 ...

The vic20 and C64 keyboards are exactly the same pinout .
I know this from my keyboard project on here!

viewtopic.php?t=15160

sorry m8 that link is five years old , most usb now will not work.

Just for the people who are interested the AE on the part no. is the designation for 28 pin dip and if it has a 1 on the end ( i.e. MT8808AE1 ) it is a 'lead free' part ( no Pb ) and , supposedly , better for the environment .

It might be worth asking mouser as they do not appear in the catalogue but i can get a page up with the MT8808AE1 that shows 17 in stock. https://www.mouser.co.uk/ProductDetail/Microchip-Microsemi/MT8808AE1?qs=pU29NIZ4ZwDlQSPjr7ESlQ%3D%3D mouser sku is 494-MT8808AE1 and here is a list of suppliers w...

That does not apply to modern usb keyboards , only the early one's that work with the USB to PS/2 adapter have the PS/2 protocol and will work. In the early days of USB they needed a way to be compatible with the PS/2 protocol as the majority of computers still had them , that is why they shipped th...

The project is now on my website https://www.levosretrocomputerprojects.co.uk/index.php/c64/18-c64-vic20-pc-keyboard-adapter I have used this trick with the keyboard sockets , but i do not think it will work with the IC's especially with the 20 pin connector in the middle! If enough people want one ...

I also , in all honesty , can't get all the equipment people might have and show every variation on it . The project has to be limited somewhere .

If enough people want a different version i will track a new pcb for it. Please leave a request on the forum if you would like something different.