i have an alpine mrv-f345 on my bench with a strange problem. the bottom cover shorted to the power supply transformer and blew a trace. i repaired the trace and it powered up fine but the digital display won't let me scroll thru and adjust any settings it just goes to the first screen and gets stuck. there is a seperate set of potentiometers and switches for the crossover frequency that is connected to the main circuit board with ribbon cables. when i unplug these cables the digital display works fine and scrolls thru the option list fine and settings can be changed but of coarse i get no audio out this way. i noticed that it looks like the ic chip for the display is on the main board. could it be that the shorting caused the ic chip to go bad? i checked all of the output transistors and power supply fets and they seem ok. no high current being drawn. i did notice on the digital display that when the crossover ribbon cables are plugged in that the voltage shown on the display is about a volt lower than what i'm putting in.
Many times, when a processor fails to respond or locks up, it's due to a shorted switch. The shorted switch prevents it from accepting other commands. If there are multiple plugs going from the control board to the processor board, replace one at a time to see if you can narrow down the control or set of controls causing the lockup.
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