Adjust meters

Does anyone know how to adjust the power meters on a Pioneer QM800 amp.
The meters do work but one is showing lower power than the other
If you are very lucky, there may be an adjustment trim pot near the meters to adjust.
Have you checked that it is not the pre amp output by switching inputs left to right? If that is good then as mentioned a trim pot with a very small screw head would be at the base of the meter needle.