Replacing contacts on Yamaha PSR 85
My brother, who is very ill and currently in a nursing home has a Yamaha PSR 85 keyboard that needs a contact replaced, as one key will not play. We have no one around here to work on them except the guy who has done the job before, and I can't find him. My husband is good at fixing things but is afraid of breaking something on this. He took the cover off and found it difficult to access the contacts. Can anyone tell me how to get to the contacts? Also, where can we buy some? My brother has some, but doesn't know where to get more. It would be worth a lot to my brother to get it fixed. Thanks for any help you can give us.