As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THIRD OBSERVERS AUDIO CONTROL PANEL SELECTOR LIGHTS DO NOT WORK IN NORMAL OR TEST MODE. BACKGROUND LIGHTS WORK NO SELECT LIGHTS WORK. TRIED NEW ACP & CONTROLLER. ORIGINAL EQUIPMENT BACK IN PLACE, IAW MEL. REPLACED IAW ASM 33-14-08 ACP BAD CAUSING 37LP XFMR FUSE T TO BLOW. REPLACED FUSE IAW MM 33-14-51. R&R THIRD OBSERVERS ACP MM 23-51-12 OPERATIONS CHECKED GOOD.