Question about Roland Music
Counting the keys from left to right, from switch on every third key won't work, run your finger up and down the keyboard and then three keys don't work out of every five, press lots of keys randomly and the left to right pattern is working, not not, working working working, not not, working, not not, working working working, not not, various numerical patterns of keys not working. The three tranistors on a heatsink in the power supply were all dry joints but soldering them didn't help.
The keys are scanned in a matrix. It sounds like two of the matrix lines are broken. They may be broken on the board which the keys contact. These are often conductive rubber "pills" pressed onto finger like patterns of circuit traces. The traces have a black coating in the contact area. If the keys have been "mashed", sometimes the board is cracked. IF the crack goes through one of these contact areas, that is fatal. That board needs to be replaced.
A loose cable where two wires of the matrix aren't contacting would do it as well.
Posted on Jul 29, 2009
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