Restoring HP-65

[albertofenini]

Just to add few things we tried meanwhile-
We have tried to clean some of the green spots from the motherboard with lemon juice
Apparently it worked out but on a closer look something is still there
Attached are two pictures of the CPU board
You'll notice the is not shiny as it should be.
Then since we are restoring this unit and we don't want to have too many unstable things like the keyboard or so, we have put this mother board in a working HP-65.
Turns out that it works, but it is not responsive to the last two bottom lines of keys
We know for sure that the keyboard circuit for that unit is fully working