My top Bflat on my Roland 4500 piano has suddenly ceased to work?

My digital Roland 4500 has brought me a lot of pleasure.
Up till now it has worked perfectly, but yesterday the top Bflat has stopped working. I am the only person who plays the piano. Any ideas please ?
Howard Davies, March 2013
http://www.roland.co.uk/articles/default.aspx?c=4

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Peccavi, March 2013

Fix Fault - Musical Instruments

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