I recently picked up a Roland A-90 for a very small trade knowing it had power issues and that the keys were not working.
I was able to fix the power supply issues in about 5 minutes as I have read other threads pointing to 3 DC Power Regulators which often need resoldered. That fixed that problem.
The keys have been more challenging for me to troubleshoot and I would love any tips to point me in the right direction. I am pretty handy with a multi-meter and soldering iron, but am in no way an electrical engineer.
I have put the unit in test mode and have confirmed that all buttons besides the keys, including the Mod/Expression wheels are working and send data. In test mode I have also generated sine waves to test the output of the headphone jack, and stereo 1/4" outs. In test mode not a single key will trigger any sort of velocity data, all are dead. I am pretty confident everything is working except for the dead keys.
I have unplugged, cleaned, and reinserted every ribbon cable going from the keys to the main board. I have tested for continuity a few (not all) of the pins from the ribbon header on the main board to the ribbon header on the keybed board. The few I tested made me feel the ribbon is making solid contact between the boards. I have taken one of the boards of the keybed and inspected the rubber/carbon switches. They visibly look very clean, and I did not proceed to attempt to clean the carbon contacts since all keys are dead.
Any thoughts of what to try or test next? Could all the Carbon contacts need cleaned and that is the cause of the dead keys? I guess I am assuming some of them would still be working if this was the issue?
I was able to fix the power supply issues in about 5 minutes as I have read other threads pointing to 3 DC Power Regulators which often need resoldered. That fixed that problem.
The keys have been more challenging for me to troubleshoot and I would love any tips to point me in the right direction. I am pretty handy with a multi-meter and soldering iron, but am in no way an electrical engineer.
I have put the unit in test mode and have confirmed that all buttons besides the keys, including the Mod/Expression wheels are working and send data. In test mode I have also generated sine waves to test the output of the headphone jack, and stereo 1/4" outs. In test mode not a single key will trigger any sort of velocity data, all are dead. I am pretty confident everything is working except for the dead keys.
I have unplugged, cleaned, and reinserted every ribbon cable going from the keys to the main board. I have tested for continuity a few (not all) of the pins from the ribbon header on the main board to the ribbon header on the keybed board. The few I tested made me feel the ribbon is making solid contact between the boards. I have taken one of the boards of the keybed and inspected the rubber/carbon switches. They visibly look very clean, and I did not proceed to attempt to clean the carbon contacts since all keys are dead.
Any thoughts of what to try or test next? Could all the Carbon contacts need cleaned and that is the cause of the dead keys? I guess I am assuming some of them would still be working if this was the issue?