Narrative:

After a normal preflight we departed. At some point in the late climb or top of climb we observed a 'TCAS fail' indication which the captain reported as a discrepancy via ACARS to maintenance and entered into the maintenance log. Early in cruise we observed a number of annunciators illuminate simultaneously with an associated master caution. The following annunciations were observed: tru fail (and 0 dc amps noted on TR1)right electric hydraulic low pressureleft probe heat associated captain pitot; left elev pitot; left alpha vane; temperature probeequipment cooling exhaust OFF2 of the 4 window heat OVERHEAT2 of the 4 wing fuel pump low pressuregpws off.the yaw damp annunciator illuminated either concurrent with the initial failure or at some point shortly after (my recollection is not clear on the timing). A cursory check of the overall aircraft condition also revealed that we had also lost the ACARS system. After a few minutes we received a call from the cabin indicating some service items not receiving power.it was apparent from the pattern of loss of all of these associated electrical consumers that we had experienced a significant electrical fault and possible loss of a main bus; but there were no specific indications from the electrical system itself other than the TR fail annunciator and TR1 dc amps indication.at this point the captain took control as pilot flying and I referenced the only electrical associated QRH (tru fail); which is very short and did not provide any pertinent insight into the overall nature of the failure. We took note of our geographical location and identified [ATC] as the most reasonable diversion location in the event this should become necessary.the captain made a decision to descend to FL250 and then start the APU for possible electrical redundancy (we eventually decided that switching the APU onto the bus would probably be ineffective at best; and possibly harmful). The captain transferred control back to me and I initiated the descent. The captain proceeded to contact dispatch via airinc (a process initially made more cumbersome without available ACARS); who set up a conference with maintenance. I did not monitor this communication as I was flying and handling ATC communication. After a period of discussion with maintenance it was apparent to me that we had lost radio contact with maintenance. Around this time we noted that the stabilizer out of trim annunciator was illuminated. The annunciator remained on and no trimming was observed during this time; I disengaged the autopilot as the QRH directs and noted normal electric trim function. The aircraft was hand-flown for the remainder of the flight.with the unsure state and stability of the electrical system and unreliable means to communicate with dispatch and maintenance; we decided the best course of action was to [advise ATC] and divert toward ZZZ; which we did. At some point during our descent; we observed the bat discharge annunciator illuminate. We also observed an unusual cyclical sound through our audio panels late in the flight.a visual approach to runway xy at ZZZ was planned and briefed. We extended the flaps earlier than normal to ensure their function; and did the same with the landing gear extension. Upon gear extension we noted automatic brake disarm and anti skid inoperative annunciators illuminated; which we had previously discussed and briefed as a possibility. The landing was uneventful.the electrical system would not accept power from either the APU generator or ground power. Upon shutdown; we noted the right generator transfer bus off and source off annunciators illuminate.during the event the captain continued thorough communication and coordination with the cabin; and informed the passengers of the diversion. This narrative describes my best recollection of the timeline of this event (it is possible that there are some minor timeline errors).

Related reports:

Google
 

Original NASA ASRS Text

Title: B737 First Officer reported that during climb a 'TRU FAIL' (Transformer/Rectifier Unit) light came on along with the Master Caution. All associated electrical systems failed.

Narrative: After a normal preflight we departed. At some point in the late climb or top of climb we observed a 'TCAS FAIL' indication which the captain reported as a discrepancy via ACARS to maintenance and entered into the maintenance log. Early in cruise we observed a number of annunciators illuminate simultaneously with an associated Master Caution. The following annunciations were observed: TRU FAIL (and 0 DC AMPS noted on TR1)Right Electric Hydraulic LOW PRESSURELeft Probe Heat associated CAPT PITOT; L ELEV PITOT; L ALPHA VANE; TEMP PROBEEquipment Cooling Exhaust OFF2 of the 4 window heat OVERHEAT2 of the 4 Wing Fuel Pump LOW PRESSUREGPWS OFF.The YAW DAMP annunciator illuminated either concurrent with the initial failure or at some point shortly after (my recollection is not clear on the timing). A cursory check of the overall aircraft condition also revealed that we had also lost the ACARS system. After a few minutes we received a call from the cabin indicating some service items not receiving power.It was apparent from the pattern of loss of all of these associated electrical consumers that we had experienced a significant electrical fault and possible loss of a main bus; but there were no specific indications from the electrical system itself other than the TR FAIL annunciator and TR1 DC AMPS indication.At this point the Captain took control as Pilot Flying and I referenced the only electrical associated QRH (TRU FAIL); which is very short and did not provide any pertinent insight into the overall nature of the failure. We took note of our geographical location and identified [ATC] as the most reasonable diversion location in the event this should become necessary.The Captain made a decision to descend to FL250 and then start the APU for possible electrical redundancy (we eventually decided that switching the APU onto the bus would probably be ineffective at best; and possibly harmful). The Captain transferred control back to me and I initiated the descent. The Captain proceeded to contact Dispatch via AIRINC (a process initially made more cumbersome without available ACARS); who set up a conference with maintenance. I did not monitor this communication as I was flying and handling ATC communication. After a period of discussion with maintenance it was apparent to me that we had lost radio contact with maintenance. Around this time we noted that the STAB OUT OF TRIM annunciator was illuminated. The annunciator remained on and no trimming was observed during this time; I disengaged the Autopilot as the QRH directs and noted normal electric trim function. The aircraft was hand-flown for the remainder of the flight.With the unsure state and stability of the electrical system and unreliable means to communicate with Dispatch and maintenance; we decided the best course of action was to [advise ATC] and divert toward ZZZ; which we did. At some point during our descent; we observed the BAT DISCHARGE annunciator illuminate. We also observed an unusual cyclical sound through our audio panels late in the flight.A visual approach to runway XY at ZZZ was planned and briefed. We extended the flaps earlier than normal to ensure their function; and did the same with the landing gear extension. Upon gear extension we noted AUTO BRAKE DISARM and ANTI SKID INOP annunciators illuminated; which we had previously discussed and briefed as a possibility. The landing was uneventful.The electrical system would not accept power from either the APU generator or ground power. Upon shutdown; we noted the right generator TRANSFER BUS OFF and SOURCE OFF annunciators illuminate.During the event the Captain continued thorough communication and coordination with the cabin; and informed the passengers of the diversion. This narrative describes my best recollection of the timeline of this event (it is possible that there are some minor timeline errors).

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.