Bob -
I think the first thing to do is to attempt to telnet into the QMX. This is described in chapter 8 of the operations manual. If you are able to establish a connection, then I think you're ahead of the game. At that point, I think the problem is probably just on the display board or the connectors that go to it. Check for bad joints or shorts on the connectors and components on that board.
If you can't, then the problem might be the SMPS boards. Again, check for open joints or bridges.?
I'm no expert at this, just have made enough mistakes of my own to start to know what to look for. Many other people in the group are far better at diagnostics than I am.
John, KI3J
