First check for harness problems - shorted wries.
Next, check for board damage on the bottom right corner - the corner where the heatsink is for the audio amp. The traces for the controls snake around that area and if you have a crack in the board or a gouged trace you'll have problems.
They are tied high (meaning the logic level is kept above 2.5v signifying a logic level of '1') by a series of resistor packs. You probably have a bad trace between the chip and the resistor pack or a bad resistor pack.
RJ