Since you both heard a 'crackle':
I think about the only thing that could crackle with movement of the QCX in receive mode is a mostly direct short between the input 12V and ground.? This could come from the board flexing a bit and something on the board contacting the chassis (or similar mechanical movement).? I would first visually inspect very carefully with board in chassis to see what could possibly touch where it is not supposed to. Current flow for such a short would go mainly through Q105 and Q103, possibly frying one or both of them.? It would be reasonably easy to check the +12V rail at one of the power jumper blocks, or better at the input and output of Q105 when you try to power on.? If you see a good 12V at all of those spots, the problem is elsewhere - but from what you are saying, it's likely in that area of the circuit.
