They can be repaired by a good electronics shop, as there are four transistors that provide the power to the servo which burn out occasionally. Not an easy job, but the only other option is to bin the PGM and fit a new one - if you can find one!
It's not something I've seen done, but I know of others who have...
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MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball
