"Woody"

It sounds to me like a bias fault - one of the output transistors is
getting hot

** Only one ?

That is not even possible with a bias problem.

and a sensor - usually a transistor fitted into the heatsink - is sensing
the rise in temp and trying to switch the output transistor off.


** Got no hope of doing that - since it only stabilises the bias current
setting.


Net result is a seriously distorted output.


** Wot a load of claptrap.




...... Phil