This machine is from the 1980's and in its time was a high end CD player.  Unfortunately, the years have not been kind!  When this one hit the bench, it had trouble reading any disks, and when you managed to get a decent read, there was a killer 100Hz hum on the recovered audio.  I think it hummed basically because it was never taught the words...

As the hum came in at 100Hz, 'pickup' can be ruled out from the process as that would have been at 50Hz.  The main power supply is full wave from the transformer so the output is at 100Hz, pointing directly at the main filter caps as the likely culprit.  Power board pulled and main caps removed and tested....er....fail!!  After replacement of the 3 main filters that hum had all but gone, but for some reason the recovered audio still sounds broken up, like it was out of sync with the decoder.  Checking the DAC board, 5 caps were pulled for testing and all 5 failed in capacity and ESR.  There was an article I remember reading about the old Philips capacitors from the 80s being junk now, some 40 years later.  Just can't get good parts those days..

The decision was therefore made to do a complete re-cap of the box.  All the boards were pulled and the electrolytics replaced.  The boards were then cleaned down and the conformal coatings redone to make all the solder sides nice and shiny again.