[hbens]

I was a ship without a rudder until the diagram arrived, now the path is clear.  I always welcome input, I did spend time as an Avionics Tech so I have chased a wire or two in the vacuum tube days.

I was an AT when I was in the US Navy. They taught us to split the problem in half and keep doing that until you narrow down the problem.
I worked in a shop on a bench so we had simulated inputs. One of the first checks was "knob-ology" to see if a knob was in the wrong position.
I still use that now common sense approach to fixing things.