Completely unresponsive click wheel

Ipod classic 80GB is not responding to any clicks or rotations on the wheel. No reset possible. Resetting it from itunes, no effect. Changing the clickwheel to a new one (and a second new one, no effect. Checked the cables and connector seatings twice and triple, no respond.

Is it possible, that there is any interference with a defective hold button? Display reflects hold button on/off showing the lock signs…

I will still go for a alcohol cleaning of the motherboard.

Any other hints as for further options to diagnose, which component might be the cuplrit?

Regards and thanks for all answers in advance,

Alex