NSM ES 160 Delay volume increase when playing

Hello...
My NSM ES 160 has a Delay in the volume increasing when playing a record... starts very low and volume will increase after about 10 seconds after play the record has started....

The amplifier has an "Automatic Volume Control" (AVC) and an volume control stage located on LP1.
This balances the difference in volume of the two channels (when stereo) and the difference in loudness of the different records.
The volume starts at a low point and gets increased to a certain stage - so in the end all records have the same volume. Otherwise one record would sound more loud than the other at the same setting.

10 seconds seems a little bit too long to me but I don't know how many seconds would be fine.

If you have the schematic on hand, you could check the parts on LP1 if there is a problem with AVC and/or volume control stage.
There is also a short description in the manual about the signal's way.

Hildegard Stamann