Filter tuning problems (SMR4 mkII)

I have a problem with tuning my SMR4 mkII filter board. When I switch off both oscillators, turn the resonance of the filter to maximum and play a note on the keyboard I can hear the self oscillating of the filter. But the pitch of the sound changes every time I press the same key. I have tried to adjust the trimmer but it doesn’t get better.
I’m getting crazy :slight_smile:

Have you checked for LFO settings that maybe modulating the cutoff or res parameters?

oh, thank you :slight_smile:
I’m such an idiot …