NEWARK - (AP) - Power problems on Amtrak's NortheastCorridor continue to cause headaches for rail travelers despitemillions spent to upgrade aging equipment.

Three incidents this week caused significant delays betweenPhiladelphia and New York.

Amtrak says service was disrupted Thursday morning and afternoonbecause a computer problem prevented enough power from reachingtrains.

Trains sat idle for several hours on Tuesday because of atransformer fire in New Jersey.

Amtrak has spent millions to upgrade old electrical equipmentbetween New York and Washington, D.C., since 2002 and receivedadditional funding in 2009. But spokesman Cliff Cole says it'simpossible to completely prevent problems from occurring.

There have been seven disruptions caused by downed wires orvoltage dips in New Jersey since March.Amtrak fixes power problems on rails