I have a 1973 Pioneer SX424 amp/tuner, it still works a treat but it tends to lose a channel after being on for a while. This can be corrected by turning the mode switches. I'm assuming that the rather complex physical switches are making intermittent contact. Mates who are telecom engineers, trained in the old Stouger days, told me to clean the contacts with meths, this has not cured the problem totally, is there any more I can do.
Damon.