Unplug the power cord. The Roland Cube's power cord is hardwired to the back of the amp, so it needs to be unplugged from the electrical wall outlet. Do not work on a powered amplifier.
Remove the back panel. To access the Roland Cube's speaker and speaker connections, remove the black panel from the rear of the amplifier. Use a Phillips-head screwdriver to unfasten the mounting screws.
Check the speaker's connection terminals since many amplifier problems can be traced back to these. Daily use of the amplifier will cause the speaker connections to loosen. Use a flashlight to illuminate the amplifier's single speaker. Check the speaker terminals for loose connections. If the connections are loose, use a pair of pliers to crimp and tighten the speaker wire connection points.
Remove the electronics chassis. Use a Phillips-head screwdriver to remove the chassis mounting screws. These are located on the top of the amp surrounding the control panel and on the backside of the amplifier's casing. Slide the chassis out toward the back of the amplifier.
Clean the amplifier's electronics. Use compressed air to blow off any dirt and debris from both sides of the circuit board. Many problems are difficult to see if the electronics are coated with dust.
Inspect the wiring. Look for damaged wire shielding and burn marks. Heat generated during the amplifier's operation can cause the plastic shielding that covers the wiring to melt, allowing bare wires to come in contact with other electrical components. This contact causes shorts in the wiring system. Carefully reposition the damaged wire. Use a piece of electrician's tape to cover all bare wiring.
Check all soldered connections, since vibrations can loosen them. Gently move any soldered wires at their connection points. If the wire shifts at the connection point, it needs to be soldered back in place.
Check the circuit board for corrosion. The Roland Cube uses large vent slots to allow heat generated by the amplifier to quickly exit the casing. These slots also allow moisture in. Look for corrosion on the circuit board's soldering. Use a cotton swab dipping in rubbing alcohol to clean off any corrosion.
Reassemble the amplifier. Place the electronics chassis back into the amplifier's casing and replace the mounting screws. Replace the black back panel.