As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
MASTER WARNING LIGHTS (RED) AND BELL WERE ACTIVATING EVERY 90 SECONDS WITH NO EICAS OR OTHER RED LIGHTS ILLUMINATING.(<P>REMOVED AND REPLACED MASTER MONITOR A & MAWEA PCC IAW B747 AMM 31-51-02. OPS CHECK GOOD. PART EFFECTIVITY VERIFIED PER IPC 31-51-02-01.</P>)