ALT BUST.

Narrative

IMMEDIATELY AFTER TKOF; BOTH AIR CONDITIONER PACKS TRIPPED OFF AND COULD NOT BE RESET. FO ADVISED DEP CTL THAT WE WOULD LIKE TO STAY WITH HIM AND MAINTAIN 8000 FT. (OUR LAST ASSIGNED ALT) TO 'CHK OUT A LITTLE PROB.' AS WE CONTINUED CLB; I DIRECTED FO TO CONTACT COMPANY FLT CTL (DISPATCHER) AND ASK ABOUT THE POSSIBILITY OF CONTINUING TO DEST UNPRESSURIZED. AS WE APCHED 8000 FT THE FLT ATTENDANT IN CHARGE CALLED AND BECAUSE OF POOR QUALITY OF INTERPHONE; I SAID TO COME TO COCKPIT TO TALK. I HAD HEARD HER REFER TO THE BURNING SMELL IN THE CABIN AND I SUSPECTED THE OVERHEATED AIR CONDITIONER PACKS. AS SHE KNOCKED ON DOOR AND ENTERED; I WAS MOMENTARILY DISTR AND PASSED 8000 FT BY 300-400 FT. I IMMEDIATELY BEGAN CORRECTIVE ACTION AND ATC CALLED SAYING WE HAD GONE THROUGH OUR ALT; AND 'WERE WE OK?' I MADE THE DECISION TO RETURN TO SBN AND A NORMAL LNDG ACCOMPLISHED. BY DIRECTING FO TO CALL COMPANY SO QUICKLY; I 'TOOK HIM OUT OF LOOP.' THEN; WHEN DISTR BY FLT ATTENDANT; I HAD NO BACK-UP ON ALT MONITORING. COCKPIT RESOURCE MGMNT. SUPPLEMENTAL INFO FROM ACN 285318: ATC INFORMED US WE WERE ABOVE OUR ALT. WE DSNDED TO 8000 FT AND RETURNED TO SBN FOR MAINT.