Quoted from maestro:Title pretty much sums it up. Plays fine but sometimes has to be on a while before sound starts working. Usually I can play a game, turn the machine off, then back on and it works. It's more likely to happen when it's cooler in the house and outside.
Most likely the power supply needs to be serviced (usually capacitors that have dried out over time) but could be other things. Do you have a voltmeter/DMM? Do you know how to take AC and DC measurements of voltage?