James and John,
I have seen this on a damaged Rev 1 QDX that I bought from a Ham that did not want to try to repair it.? At first, the QDX would power up and connect to the PC using PuTTy.? After trying for a few minutes, the connection dropped, and I could not restart the QDX.? The original failure was shorted BS170s that took out IC5.? Since one of the inputs to IC5 is the TX signal direct from the MCU, I assume that 12 volts got to that pin and took out the processor.
The lesson I learned was to remove the BS170s to verify them out of the circuit (I now have a Hakko desoldering gun for this) and verify IC5 before installing fresh units.
73
Evan
AC9TU
