I think the schematic had a little problem, the pin 3 of INT pot should not be connected directly to the LED(D1), instead,
it should be connected to the point between R31 and IC4.2's Output(Pin 7), so the Vf of LED won't effect the oscillator,
and you will get a really tiny effect if you don't turn the SHAPE knob all the way up.
it should be connected to the point between R31 and IC4.2's Output(Pin 7), so the Vf of LED won't effect the oscillator,
and you will get a really tiny effect if you don't turn the SHAPE knob all the way up.