> I think we're getting close to the "Aha !" moment !!!
I hope so.? ;-)
In this setup (Q12 / CR13 out of circuit), the gates of Q15 are offset just a bit - A: -5.0V B: -5.8V? The drains are of course then far apart - A: 2.8V B: 8.46V? and the sources are tied together at -4.9V.
This means the inputs to U2 are both way off from the quiescent value of 5.7V.? U2 is not quite at the rail, but close: -10.9V and there's no drop across R43.
This should be trying to reduce the current from the current source by turning off the FET/darlington circuit, right?? Yet it isn't.? I can't quite believe that the replacement Q11 is also defective, but maybe...
