Solid state guitar amps use transistor technology rather than tube technology to amplify the signal of the guitar. Early guitar amps used vacuum tubes to amplify the sound, but when the transistor was invented, amplifier manufacturers found a more reliable and cheaper technology. Solid state amplifiers are considered to be more reliable than their tube counterparts, but problems can occur in solid state amps. Solid state amplifiers are typically cheaper to repair than tube amplifiers.
Identify the source of the problem. As soon as you notice a problem, attempt to make an assessment of the cause. If you are able to turn on the amplifier but are experiencing diminished sound quality, you at least know that the problem is not in the power section. If there is a clear sound coming from the amp but it is followed by a rattle, you should take a look at the speaker. A damaged or loose speaker cone can create a rattling sound.
Inspect the amplifier for obvious signs of damage. Turn off the power and unplug the amplifier from the power supply. Remove the rear panel from the amplifier using a screwdriver. If you can see any loose parts or parts that have become completely detached, this may be the cause of the problem. Reattach the part and then try the amplifier again.
Look for loose wires and blown fuses. Sometimes the problem is as simple as soldering a loose wire back to the relevant terminal or changing a fuse. If you are in doubt of how to tackle this problem, consult a qualified repair professional.
Replace any broken or worn out parts. If you identify any parts that are obviously damaged, such as a transistor, take the part to an electrical store or guitar store and ask for an exact replacement. It's important to replace like for like so that you know the new part is compatible with your solid state amplifier.
Clean the pots and dials. Sometimes dust and grime can cause an amp to malfunction. Use a damp cloth to clean the front panel of the amplifier. Using a dry cloth to wipe away any dust or grime that has become deposited inside the amplifier.
Reattach the rear panel. When you have successfully replaced any faulty parts and have corrected the cause of the problem. Make sure you screw the back panel on firmly to protect the interior of the amplifier from dust particles. While you have your screwdriver handy, tighten up any other screws such as those on the amplifier handle. Quite often a loose screw on the outside of the amplifier is enough to create an irritating buzz.
Keep a mental note of which screw goes where. It's easier to screw them back into their original hole.
Always ensure that power is off when inspecting the inside of an electrical device. Before testing the amplifier, make sure that the volume is low.