I recently had mine (AIWA NSX-D939) repaired for a similar problem. Your brief discript about your unit sounds like your experiencing a power-down issue. And, in consideration of the age of the unit, it is probably the capacitors related to the power supply unit that's giving the trouble. Capacitors do dry up (internally) over time. The same was true for my TV which I had recently repaired. It too had to have the capacitors replaced. Go to AIWA websight and it provides location info on local service centers which repair your specific model unit.
Milton B Rick, November 2007