There is no fuse in the power supply circuit, however, there are four diodes in the small board within the keyboard that are part of the power internal segment of the power supply. This PC board can easily be cracked if the power supply plug is inadvertently hit or pushed in a bit off center.
Sorry, this may be one for the Authorized Service Center guys to take a look at. That small PC board is not easy to get to.
Good Luck, Larry, and I'm sorry I could not be of more assistance last night.
Gary
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PSR-S950, TC Helicon Harmony-M, Digitech VR, Samson Q7, Sennheiser E855, Custom Console, and lots of other silly stuff!
K+E=W (Knowledge Plus Experience = Wisdom.)