What was found
FLIGHT MECHANICS REPORTED O2 AT 1700 IN HHN AND DOWN TO 1200 IN BWI, CHECK FOR LEAK.(<P>ACCOMPLISHED TROUBLESHOOTING PER AMM TASK 35-11-00-795-106. LEAK CHECKED & NO LEAKS FOUND. DISCONNECTED CREW O2 MASK. WHEN DISCONNECTED, F/O O2 MASK O2 PRESSURE STABILIZED. LEFT MASK DISCONNECTED FOR TROUBLESHOOTING PURPOSE. O2 PRESSURE AT 1750, O2 PRESSURE DROP DOWN TO 1350. RECONNECTED F/O'S O2 MASK PER AMM 35-11-51. REMOVED O2 STOWAGE BOX PER AMM 35-11-51. UPON CHECKING FOUND LEAK IN 2ND OBSERVER O2 BOX. SECURED LINE & INSTALLED OBSERVERS O2 BOX PER AMM 35-11-51. LEAK CHECK GOOD AT THIS TIME. </P>)