Well, I have a very nice Roland JD800, but many of the keys were not working. I've had some success at repairs and opened it, which is a labourous task. Inside, the key felt was fine, but glue had melted around the contract strips, probably causing contact failure.
I called Roland and they say it will cost about $110 for the strip and I can bring it in. Thankfully, I have a Roland dealer about 30 min away with parts. What does this entail, could I lay the strip myself?