[Yaesu] FT1000MP MkV Field headphones output adjustment

[va3pl at cuic.ca]

Hi all
On top of my MkV Field there is a little door with bunch of pots to adjust
headphones audio level as stated in the manual.
When I try to make adjustment (increase), it seems that turning the pots
does not have any affect an headphone audio level.
Any suggestion would be appreciated as there is a considerable difference
when listning on the speaker or on the ear phones.
73 de Andy - VA3PL