So, I finally have found it.

First, I could not find new CA3083 chips to replace the suspected ones. They say, that they are not manufactured anymore, which could be a big problem, for a lot of modules use these.

But than after a while, I came with the idea to use the suspected CA3083 chips on the A-143-9 QLFO.

The results were, that all these chips were working fine on the QLFO.

Than I replace the four suspected TL084 chips with new ones, and find out that two of them were broken. These two chips were the closest to the damaged potmeter.

So, you got it right, Dieter.

Thanks,

Ben