On July 22, 2025, JR East announced that the Yamagata Shinkansen “Tsubasa,” which had been operating turn-back services at Fukushima Station due to issues with the new E8 series trains, will resume direct operations between Tokyo and Yamagata/Shinjō starting Thursday, August 1.
■ Overview and Cause of the Malfunction
Incident Period: From June 17, 2025, with issues occurring in five trainsets.
Cause: Damage to semiconductor components in the auxiliary power units.
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Triggered by excessive current control and high-temperature environments, leading to malfunctioning of protective elements.
Impact: -
Confirmed that earlier E8 series (sets before No. 6) and the E6 series were unaffected.
■ Countermeasures and Operation Plans
Measures Taken:
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Protective component settings in control circuits were revised.
Fleet Affected: -
Trains are being gradually returned to service after countermeasures are implemented.
▼ Resumption of Direct Service
Start Date: Thursday, August 1, 2025
Route: Tokyo – Yamagata / Shinjō
▼ Number of Services and Timetable
Regular Trains:
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Normal schedule to resume in principle from August.
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Note: Some services will be canceled on August 1.
Extra Trains:
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August 1–8: Some reductions in previously announced additional services.
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From August 9 onward: Detailed schedule to be announced around July 28.
