sony Str-d315 Receiver Am Fm Stereo Cd Phono Tape Serviced A-b Speakers Only

Sony STR-D315 Receiver AM FM Stereo CD Phono Tape Serviced A-B Speakers only B work as of Nov 28 2022 I opened the case and it was very difficult o to put back together properly.Tried to access the A and B speaker switches inside the case but they are way to difficult to get at.Blew them out with a PC Duster pressurized can top and bottom.Wanted to either clean the contacts or bypass the switches but it would have been a lot of time and effort. Discrete components. Not PC board but jumper wires in pegboards by the dozen. Very old technology. Yet acceptable performance. Sony STR-D315 Receiver AM FM Stereo CD Phono Tape Serviced A-B Speakers only B work as of Nov 28 2022B work so I accepted that and put it back in operation. Hooked up only B speakers, my 12" woofers and 3-way mid range and tweeters. AM and FM antennae. Tested at high volume power output and passes that test. Bass and Treble and Balance controls operate as they oughtta. FM 101.1 station is still programmed after ½ to one hour unplugged. Says something about why all the programmed stations have dropped out some mornings. So I have only one pair of speakers in operation not A and B. It is the A-B switches. Help?