That brief was from before I had a schematic for the 300 or the 500. PA
component level schematic with similar D class in the 500 manual.
The 470uF cap is not on the audio o/p filter but must have been one of the
main DC rails. What effect would intermittant non electrical contact of one
of those , due to tinpest, have on functioning of the amp when there is
plenty of capacitance at the ps ?