Denial

Well.. I never got hands on them. I ended up having a friend creating a 3D model of the plunger. I managed to make two of them into my broken keys and worked just fine. Only one is missing also the rubber contact and that one I am still missing to get the keyboard fixed.

Do you have posted on the C64 issues... I have fixed quite a few of these.

Unfortunately, no... I guess I need to continue watching youtube and reading to get more ideas. Something I did found out is that the VIC on this motherboard at some point failed and now is dead. I had to look for some (expensive) replacements to get back to where I was. However, I am a bit weary to...

Yes, all the ICs I could have brought into the working VIC were tested there... particularly the VIC, ROM (only one ROM is socketed on the working one), and CPU. However, when I remove the VIC the computer does nothing I think the clock that feeds the CPU comes from the VIC, right? This is what happ...

Not in my town... unfortunately... here in Mexico, they are quite rare (the VIC-20s at least).

Vic20-Ian wrote: ↑Thu Jul 22, 2021 3:53 pm Ask in your local bar?

There are a few million Vic and C64s around.

An option would be to modify a modern PSU and use an adapter for the two pin connector... I have not yet used it, but found a 3D printable connector adapter here:

https://www.thingiverse.com/thing:4678324

from https://www.youtube.com/watch?v=pkmAbx2YLSU

As I am petty much out of ideas, I went and checked all elements of the circutry close to the VIC. The image below, shows in Yellow all the elements that where verified for shorts, broken traces, or any other issue. I even removed a few elements that were suspicious when measured in circuit (the var...

Ok, I've got 4.89 VDC on the +5V rail of the working VIC-20 and 6.70 VDC between the two pins of the regulator. Now I just noticed the working VIC-20 has a cap underneath close to the VIC.. I recall that when I cleaned I put some capton tape there to prevent any shorts. No idea if this was some kind...

Yesterday I got the PCBs for the SRAM tested delivered at my door. So I went and assembled the device to test all 2114 SRAM ICs on the VIC 20. None of them were faulty. https://i.postimg.cc/TpRMcmRn/20210803-221338-1.jpg +5V DC measured at the datasette port is 5.17V... this is what is being fed to ...

Ok.. I ordered a PCB to build a 2114 SRAM tester.. will have to wait to get these and test the memory to rule that out. Other than this.. I have no more ideas.

Okay, sure looks weird. Positive no bridged connection between pins 3&4 ? Well... I decided to go on the safe route and ended up replacing the VIC socket. Also socketed the 7402 IC next to it. This to rule out any issue with the socket (and bridges or anything like that) on the VIC Pins. Howeve...

This looks different to the original capture of VIC PIN 4 in your original post? If I take the VIC from the working computer into the faulty motherboard I get a similar signal on PIN 4. The difference in the screenshots may be related to the configuration of the scope (probably I zoomed more/less i...

Ok.. I have gone through most of the traces that include the ICs that seem to be related to PIN 4 (R/W) of the VIC. However, I am not really sure what to look for... thee are no broken traces nor grounded ones. Not sure where to take it from here. https://i.postimg.cc/FdGrRqbR/20210721-155606-1.jpg ...

6560 PIN 4 (R/W) - looks a bit strange, is this a floating input? Do you get the same pic on your good Vic (I don't have a scope so can't tell). Bingo... seems you've got something here. This is the output of PIN 4 of the VIC: https://i.postimg.cc/PC4SZKp0/20210720-212839-1.jpg To rule out the IC i...

beamrider wrote: ↑Tue Jul 20, 2021 11:48 am I don't have any more ideas I'm afraid.

I will go back and do a re-check of all the traces on the board... I guess it will take me a few days to come back again with any findings.