① Today’s Incident (August 24, 2025)
Time: Around 2:10 p.m.
Train: Yamabiko No. 63 (Tokyo → Morioka)
Section: Between Ōmiya and Oyama
Summary: The train stopped due to a mechanical failure. Operations were suspended on both the inbound and outbound lines between Tokyo and Morioka. Service was expected to resume around 5:00 p.m.
Possible Cause (Hypothesis): With outside temperatures exceeding 35°C, the load on the onboard air-conditioning system increased significantly. This may have caused the control circuit of the auxiliary power unit to overheat, leading to a malfunction of its protective device.
② Major Incident in June (June 17, 2025)
Time: Around 11:24 a.m.
Train: E8 Series Non-Revenue Train (between Utsunomiya and Nasushiobara), followed by multiple other trains
Summary: The auxiliary power unit failed, rendering the train inoperable. The issue first occurred on a 7-car E8 series non-revenue train and later affected commercial trains such as Tsubasa No. 139. A total of four trainsets experienced similar failures.
Official Cause Report: Inadequate settings for protective components on the control board allowed damage to semiconductor elements due to overcurrent and rising temperatures.
Countermeasures: The control board settings will be reviewed, and integrity checks will be conducted before resuming operations gradually starting in August.
③ Other Past Incidents
July 24, 2025
Section: Between Kōriyama and Shin-Shirakawa
Summary: A maintenance vehicle broke down during nighttime work, causing delays of up to 25 minutes on northbound trains and affecting about 450 passengers.
April 2, 2025
Section: Near Fukushima Station
Summary: Approximately 20 liters of oil leaked from an inspection vehicle, contaminating the tracks. Services were suspended for about 5.5 hours between Tokyo and Sendai, affecting roughly 43,500 passengers.
March 6, 2025
Section: Between Ueno and Ōmiya
Summary: The couplers connecting an E6 series “Komachi No. 21” and an H5 series “Hayabusa No. 21” disengaged while in motion, forcing an emergency stop. Coupled operations were temporarily suspended for safety checks.
January 23, 2025
Section: Between Ueno and Ōmiya
Summary: A weight rod on an automatic tensioning device (WTB) for the overhead wiring broke, causing the contact wire to sag. Services were suspended throughout the day between Tokyo and Sendai, with additional disruptions on other lines.
 Time: Around 2:10 p.m.Train: Yamabiko No. 63 (Tokyo → Morioka)S){kind=link}