Atari 400 System Reset issue

[+slx]

After a major restoration/retrofit session (NOS keyboard, new upper case, Super Colour CPU card and 48/52K RAM Card as well as swap of the system crystal to PAL) my 400 seems to work fine with the exception of the [sYSTEM RESET] key.

 

I have to admit that I did not test the keyboard that thoroughly so I'm not sure if that key ever worked.

 

I noticed some "black spots" in two of the conduits on the mylar keyboard connector and would appreciate feedback on whether that could be the culprit and if/how it can be tested and/or repaired.

 

 

I set up the new RAM card to run Newell OS N - so different System Reset behavior would be another possible explanation. As it is supposed to switch to Omnimon using Option+System Reset that doesn't look like a plausible explanation, though.

 

 

 

 

[+Nezgar]

test conductivity along that trace with a multimeter? If its bad, that looks like a good candidate for repair with silver conductive paint/pen.

[+slx]

test conductivity along that trace with a multimeter? If its bad, that looks like a good candidate for repair with silver conductive paint/pen.

 

Isn't it embedded between two layers of mylar? Can I pry those apart without ripping everything apart?