Furuno 588 manual gain problems

[rolmops]

i have a 2 year old Furuno 588 hooked to an Airmar tr260 transducer. It works fine as long as the gain setting is on fishing or cruising. When I
switch the gain to manual it does not react at all . I can turn the knob in either direction and the gain remains exactly the same. There is not really a 10 position rotation at all . It just turns around more than full circle. Is there something I am doing wrong or is the board defective?

 

[StewartL]

Sounds like the manual gain knob itself is faulty. The endless spinning without any change on the screen points to a broken encoder on the control panel, not the main board. You'll likely need a technician to replace the knob assembly.

 

[rolmops]

I got lucky.
A factory default reset made the problem go away.