Echoplex plop noise

[atq sound <atqsound@gmail.com>]

Hello,

I am trying to fix my Oberheim Echoplex Digital Pro.

Everytime I loop something with the echoplex there is a "plop" noise at the start/end of the loop.
Even when there is no input and it's just recording silence. This happens as well when I overdub.

I already checked this:
- it happens both with LOOP IV and LOOP 3.3
- changing RAM didn't make a difference either

I did some research on the web and found a comment of Matthias Grob to a user who had the same problem:
"If the blopp happens in other situations, too, it might be the DC aligning, a trimmer, easy to set"

Does anyone know what he's talking about?
Any advice is welcome.

Thanks and kind regards!