As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
MASTER BRIGHT SWITCH WHEN TURNED FULL BRIGHT ALL STDBY INSTRUMENTS. FOUND THAT WHEN MASTER BRIGHT CONT (P5 PANEL) ENGAGED (BUTTON PUSHED IN) THAT STBY INSTRUMENTS CAN GO FULL DIM WITH LIGHT PRESSURE ON KNOB. WITH MASTER BRIGHTNESS DISENGAGED STBY LIGHTING AND CONT NORMAL USING INDIVIDUAL CONT KNOB ON SIDE PANEL. REPLACED MSTR BRT CTRL POTENTIOMETER PER WDM. AFFECTED SYS'S OP CHECK OK PER MM.