C64R MK1 - Keyboard and reset problem

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Don't Panic. Please wash hands.
  • Hi!


    My C64 Reloaded mk1 developed a problem yesterday. Pressing one of the keys in vertical line 7 of the keyboard matrix (X, V, N, <comma>, and <cursor down>, but oddly not the <slash> key), results in a clear screen with "Ready." prompt, much like hitting <run-stop><restore>; sometimes the pressed character then appears at the cursor. When I hold <shift> and type any of the aforementioned keys, the expected graphical symbols appear on screen as they should, without this problematic behaviour.


    Also, the built-in reset switch (pushing the power switch on the C64R mk1 up from the "on" position) now causes the computer to freeze.


    Looking at the schematics I would expect the problem to lie in CIA chip #1. However, after swapping that IC out with at spare that I have showed no improvement. Is there anything else I could try or anything that I have overlooked?


    Best regards and thanks in advance!

    Jeroen

  • Try moving the CIA chip in the socket left to right while it's closed (lever down). This will scratch the contacts and make sure that the ZIF socket is not the problem.

  • Thanks, however my board is a mk1 and both CIA chips are in regular sockets (or at least they are in mine). I have removed and replaced the chip two times now, but that has not altered the computer's behaviour.

  • Since it's PB7 of CIA#1, a joystick can't possibly be the source of the problem. However, there's shift in that column, so the shift lock key might have an influence. Did you check that?


    Further, the behaviour similar to RS/Restore hints at an NMI being issued, or at least falsely-seen. This is the other CIA - try exchanging that as well.

  • Thanks Jens. I exchanged keyboards to see if that would improve things, but it made no difference. I'll check the other CIA this evening and have a close look at the board itself as well.

  • Try moving the CPU in it's socket while it's closed (lever down). You may just have a bad contact on the NMI line, leading to false NMI recognition. If that doesn't help, please try a different CPU.