Robotron garbage

Wednesday is game room night, and I had some time to continue work on the Robotron. Hooking up the monitor gave me only garbage, but at least the picture was changing. Now and then something wiped horizontally, to what looked like a different screen.

Testing the old 4116 ram was a pain. I started swapping chips from bank 1 to bank 3, and the error messages went something like this:

1-3-2

1-3-3

1-3-4

1-3-5

1-3-7

1-3-8

1-3-7

1-3-8

1-3-8

1-3-8

1-3-1

1-3-8

That is, whenever I replaced a chip, the next in line was broken. And even after replacing some (like 1 and 8) with chips which seemed ok for a moment, it gave an error when replacing a chip in a different location.

I decided that 4116s are indeed troublesome, and ordered a batch of 4164s today.

I wonder if the garbage on the monitor is caused only by the ram error, or if there's more to this. Booting Robotron in MAME actually gives exactly the same garbage pattern, but only for two seconds or so. After that it continues with diagnostics.

I am slightly worried, but mostly excited.