B737-200 FLC LOST PWR FROM BOTH GENERATORS AND WERE UNABLE TO RESTORE CAPT'S PRIMARY FLT INST AFTER APU START. COMPANY MAINT FOLLOW-UP REVEALED ACFT MAINT HISTORY. THE #1 TRANSFER RELAY CIRCUIT BREAKER HAD POPPED AND WAS REPLACED 4 OR 5 DAYS PRIOR TO THE INCIDENT. EMER WAS DECLARED AND AN EMER DSCNT WAS BEGUN. THE FLC FOLLOWED PROCS; BUT RESULTS WERE NOT AS FORECAST. ACFT EQUIP PROB CRITICAL.

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DURING CRUISE AT FL330; EXPERIENCED A TOTAL LOSS OF ALL ELECTRICAL PWR. SINCE BATTERY PWR IS LIMITED TO 30 MINS ON THIS ACFT (B737) WE DECLARED AN EMER AND STARTED AN EMER DSCNT; TURNING TOWARD THE NEAREST SUITABLE AIRFIELD (CMH). AFTER APPROX 6 MINS ON BATTERY PWR; A SUCCESSFUL START OF THE APU ALLOWED US TO PWR THE FO'S INSTS. ADDING TO THE CONFUSION OF SUCH AN UNUSUAL EVENT (I'VE NEVER HAD TOTAL ELECTRICAL FAILURE IN OVER 20 YRS FLYING) WAS THE FACT THAT THE CAPT'S INSTS (ADI AND HSI); DIDN'T WORK AS THEY SHOULD HAVE. WE ACCOMPLISHED AN EMER DSCNT; IN THE WX; WITH ONLY THE STANDBY HORIZON; AND STANDBY INSTS (AIRSPD AND ALTIMETER ONLY). THE ONLY COMPASS WORKING WAS THE STANDBY COMPASS (WITH NO LIGHT). INITIALLY; OUR CONCERN WAS GETTING TO A FIELD ASAP BECAUSE OF ONLY HAVING BATTERY PWR AND NO APCH CAPABILITY. EVENTUALLY; WE RECOVERED THE FO'S INSTS AND WERE ABLE TO MAKE AN UNEVENTFUL LNDG IN CVG. THE CREW WORKED WELL TOGETHER; DIVIDING UP DUTIES AND BACKING EACH OTHER UP. THE CABIN CREW HANDLED THE PAX WELL AND EVERYONE WAS HAPPY TO GET ON THE GND. LATER FOUND OUT FROM TECH OPS THAT THEY REPLACED TRANSFER RELAYS; BUS TIE BREAKERS; AND BUS PROTECTION PANELS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE B737-200 FLC RECEIVED A COMPANY LETTER FOLLOWING THIS EMER WHICH STATED THAT THE #1 TRANSFER RELAY AND THE #1 BUS TIE BREAKER HAD BEEN REPLACED. ACFT MAINT HISTORY REVEALED THAT THE #1 TRANSFER RELAY CIRCUIT BREAKER HAD POPPED 4 OR 5 DAYS PRIOR; AND HAD BEEN REPLACED. THE RPTR (IOE CAPT) ADDS THAT THE BUS PROTECTION PANEL (ENCLOSED IN A BLACK BOX BEHIND THE FO'S SEAT) HAD SHORTED OUT; AND MECHS INDICATED THAT THIS MAY HAVE BEEN A CAUSAL FACTOR IN THE DUAL GENERATOR FAILURE. (RPTR HAS NEVER RECEIVED ANY REAL SOLID CONCLUSION AS TO WHY BOTH GENERATORS FAILED.) THE FLC WAS ABLE TO START THE APU AT FL310; BUT A MAIN CONCERN WAS THE FACT THAT THEY WERE IN WX AND COULD NOT RESTORE THE CAPT'S ADI AND HSI; AND THEY ALSO HAD INITIALLY LOST PITOT HEAT. THE DETAILS OF THIS INCIDENT HAVE BEEN REPRINTED IN A COMPANY MAGAZINE ARTICLE AND REQUESTED BY THE TRAINING DEPT. SUPPLEMENTAL INFO FROM ACN 326799: WE IMMEDIATELY DECLARED AN EMER WITH ZID AND ASKED AND RECEIVED CLRNC FOR AN EMER DSCNT DOWN TO 10000 FT. DURING THE DSCNT WE RECOVERED THE FO'S INSTS AT WHICH TIME WE REQUESTED VECTORS TO THE CVG ARPT; WHERE MAINT WOULD BE AVAILABLE.