Follow the next steps to resolve:
Turn on display. Press the + and – buttons simultaneously for 2 seconds.
A line appears with tC – flashing n underneath.
Press the + and – again for 2 seconds.
Display shows VOL.
Now press M briefly.
Display shows a number and under the line VOL 1.
By pressing the + or – you change the number. (don’t hold back but tap).
Short press M.
Display shows number again and below the line VOL 2.
If necessary adjust again with + or – number.
Repeat until VOL 5.
If all 5 levels have been adjusted, confirm by long pressing M.
Press M again and you are back in the basic menu.
The correct values of voltage levels are:
VOL 1: 31.5
VOL 2: 33.5
VOL 3: 35.5
VOL 4: 37.5
VOL 5: 39.5