Blank screen but very weird presentation

  • Hey folks

    So my inlaws have a pi2 that I maintain. They brought it to me for an update, and it won't detect/trigger my monitor or TV.

    The funny thing is, I put the SD card into another pi 2 I have and that works fine.

    Then I put another SD I had lying around with raspbian on it in the "problem" pi 2 and that drove the screen fine too.

    I don't know wtf the commonality is here, please help there's obviously a hole in my knowledge.

    Everything else is being kept exactly the same cables, etc.

    thanks