FO OF ACR WDB ACFT INADVERTENTLY CLBED ABOVE ASSIGNED ALT DUE TO COCKPIT DISTR.

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WHILE BEING RADAR VECTORED ON THE O'HARE 9 DEP; OUR ACFT CLBED THROUGH OUR ASSIGNED ALT OF 5000 FT TO 5300 OR 5400 FT. I WAS THE PF. AS I NOTICED THE DEV AT ABOUT 5300 FT AND STARTED TO CORRECT AND RETURN THE ACFT TO 5000; WE WERE CLRED TO 6000 FT BY ATC. THE ATC CTLR STATED THAT THERE WAS TFC AT 7000 FT AND TO BE SURE TO GO NO HIGHER THAN 6000 FT. CONTRIBUTING TO THIS ALTDEV INCLUDED AN ELECTRICAL FAULT (PHASE 3 FAILURE OF THE #1 ALTERNATING CURRENT BUS) RESULTING IN SOME EQUIP FAILURE. THE OTHER CREW MEMBERS WERE WORKING ON THE PROBLEM. I COULDN'T HELP LISTEN TO THE CREW MEMBERS AND WAS DISTRACTED FROM FLYING THE ACFT. SUPPLEMENTAL INFO FROM ACN 220209: ORD TO CLE. SHORT FLT. HAD TO ADHERE TO A DEFERRED MAINT PROBLEM; WHERE 4 CIRCUIT BREAKERS HAD TO BE RESET AFTER TKOF. ON TKOF OUTFLOW VALVE WOULD NOT PRESSURIZE IN AUTOMATIC. AS THE ENGINEER; I INFORMED THE CAPT AND WENT TO STANDBY. THE COPLT WAS FLYING AND GOT DISTRACTED WITH THE EVENTS OCCURRING. SEVERAL OTHER ITEMS FAILED WHEN IT WAS DISCOVERED THAT AN ALTERNATING CURRENT BUS BREAKER HAD POPPED. ALL THIS HAPPENED THE SAME TIME LEVEL OFF WAS TO BE MADE AT 5000 FT. 5300 FT WAS REACHED BEFORE IT WAS CAUGHT AND CORRECTED. LESSON LEARNED; WITH COMPLEX DISTRS AT LOW ALTS; MINIMAL DISCUSSION AND 1 PERSON ASSIGNED TO FLY AND NOT GET TOO INVOLVED (DISTRACTED).