My NAD 512 cd player will play a disc for 10-15 minutes, then the transport begins to foul up. With the cover off, I observed the laser pickup retract to the start position, wildly try to focus, and the disc slowly stopped spinning, then stopped, showing "disc" on the display. It doesn't matter what disc I use. This transport was repaired by the Service Bench in Cambridge roughly 3 years ago. When I had the cover off this time, I noted some brown material drained from the 2200 Uf caps in the power supply section, next to the heat-sinked power transisters, Q501 and 502.