The D50 is a synthesizer that was first introduced by Roland in 1987. It is no longer in production but remains popular with vintage synth enthusiasts. The D50 was the first Roland synth to incorporate on-board digital chorus and reverb effects (see References 1). The control panel incorporated a joystick for modulation and pitch bend effects. Before taking your D50 in for potentially expensive repairs, you may want to try out some home repairs of your own. Often a simple reset can fix electronic glitches.
Check the power connection. Often this simple check is enough to fix power problems, such as intermittent power loss. Push the plug firmly into the wall socket and the adaptor firmly into the Roland D50. If one is available, plug the adaptor into a device of the same voltage to test it.
Turn off the synthesizer and remove the memory data card. Do so by pushing the "card" button next to the card slot and pulling the card out (see References 2). Blow on the inside edge of the card to get rid of any dust. Push the card back into the slot and turn on the synthesizer.
Turn off and unplug the D50. Place it on its front, taking care not to put the entire weight of the unit on the joystick. Unscrew all of the bottom screws with a cross-head screwdriver, excluding the feet. Remove the five small screws that run along the back panel of the D50. Set the screws aside in a safe place. Lift the bottom panel of the synthesizer away and place it to one side.
Unscrew the large circuit board. Don't disconnect the wires; they are long enough to allow the board to be moved to the side to allow access to the key contacts.
Unscrew the small circuit board and tape it so that it remains out of the way. Remove the cable plugs that connect this board. You now have access to the keyboard assembly.
Examine each key contact and manually simulate the action. When you hit a key, the key contact strikes the contact board. Contacts that aren't making good contact will be quieter. They may also fail to return to their original position.
Clean and lubricate all of the key contacts using a plastic-safe contact cleaner. Dirt and dust can create a barrier between the contact board and the key contact. If you spot any damaged key contacts, pry the damaged contacts out with your fingers and replace the springs. Salvage the springs from another keyboard, or from a key on the D50 that you rarely use. Replacements are difficult to find because most instruments have contact bubbles, rather than springs.
Examine the circuit boards. Look for loosefitting board-mounted components. Turn the board face down and use your soldering iron to melt away any loosefitting connections. Wipe away any solder residue with the cotton cloth and then re-establish the connection by soldering the connectors back on to the metal strips that run along the base of the board.
Place each edge of the synthesizer on a thick book to prevent the joystick getting crushed while you unscrew the base.
Make sure the D50 is unplugged before you unscrew the base.