FT-1000MP MKV headset sound level
 

My FT-1000MP MKV-Field has a problem. May be could help me before I contact
a dealer.
The control button of my headset exits A and B (below left of the rtx)
doesn't produce any effect (or show both the same level of audio). The sound
is now loud and no more softy as before in the speaker. So I can more adjust
the sound.
Is there a device or component that blew out or a cabling or menu to check ?

Thanks
Thierry