Most arcade cabs don't have embedded audio amps. Systems have to amplify their audio output theirselves to drive the cab's speaker(s).
These components can die from overheating or voltage surges on the 12V line.
Dead power amps tend to output no audio at all and short out, tripping the cab's or supergun's power supply protection. Crackling audio is most often a digital issue (contacts, cut traces...) and faint audio is often caused by aged/bad capacitors or broken volume pots.