The signal I get is actually an AM signal, superimposed on the regular oscillator output I find a lower frequency component which I first thought to be a power supply problem but that seems not to be the case.
Hopefully the upload of the schematic worked, so people can see the circuit. The hand written entries are not mine, I assume to have the original, unmodified circuit.
I disconnected the square wave generator at R15, 4.7K, and the oscillations persist in the sine wave, so the devil sits somewhere in the let part of the diagram, Q1 to Q5 I suppose. I take my scope signal of between Q4 and Q5, so none of the output switches etc. should be at fault, it is the oscillator.
Insights into the workings would be appreciated.
Uwe