What was found
ON DEPARTURE CLIMBING THROUGH 800 FEET, DEU 1,2,3 SHOWED RED(X) ACCOMPANIED BY MASTER WARNING LIGHT AND BELL, MASTER CAUTION LIGHT, AND ALL ALERTS INDICATING ON EAD. COULD NOT SILENCE WARNING HORN. INTERROGATED CFDS AND FOUND NR 1 DEU FAULTY. REMOVED AND REPLACED NR 1 DEU IAW MM 31-61-02-4, RTS PASSED.