etherwave brightness and waveform problem

Hello,

A while ago I build the etherwave. The volume and pitch circuits work fine but the brightness and waveform pots don't. When i turn the waveform all the way right and the brighness all the way left. the output volume is almost silent.

Can anyone tell me what voltages I should measure on pin 2 and 4 of the lm13700

What I measure is:

-0,5V to 0,5V on pin 2 (depending on the bright and wave pots)

0V to -0,5 on pin 4 (depending on the bright and wave pots)

This is what happens to the audio output when I turn the waveform pot clockwise. (0V to -12V)

The output becomes a flat line even before it is fully turned to the right extend. I don't think this is supposed to happen. What could be the problem here?

scope video

I suspect the amplitude at the mixer output being too low. Connect your oscilloscope across R24. There you should find a UUUUU-wave with 0.6 to 0.7Vpp going from 0V to -0.6V or -0.7V.

Thank you thierry,

After some measuring it seems that the mixer output was indeed to low. Probably caused by some buffer stages I put behind the oscillators to  make the sound smoother.