What was found
TRANSPONDER BACKLIGHT NOT WORKING. REPLACED ATC CONTROL PNL, REF AMM 34-52-12, CONTROLER OPS CKED OK, BUT LIGHT INOP ON WINDOW THAT SHOWS NUMBER, NINTIME TO TROUBLESHOOT, REQUESTING MEL 3310A. OK TO MEL COMPLIED WITH MEL 3310A. OPS CHECK OF INTEGRAL LIGHTING NORMAL. UNABLE TO CLEAR TO DUE ITEM LABELED MAJOR REPAIR AND SDR. SEE PREVIOUS WORK ACCOMPLISHED FOR REPLACEMENT OF TRANSPONDER PANEL OP'S CHECKS GOOD.