I’ve had an older Kenwood speaker laying around that I bought as a companion to my TS-850 when it was new. It had developed a nasty intermittent crackle, traceable to its A/B switch, although all the switches needed cleaning . I’m now using it with my Icom IC-7300. This is a sealed pushbutton switch that I had tried to clean several times before. The only point of entry without removing and disassembling the switch is a tiny hole on top of the switch.
Enter my superhero … Caig Labs De-OxIT! I I remember I used this stuff when I ran a calibration laboratory. Best contact cleaner ever! I bought a 25ml bottle with a needle applicator on Amazon for $21 … not cheap, at all. But … if you can get it onto the contact, it will clean it, protect it, and lubricate it. I know … I know … it sounds like a commercial, but believe me … IT WORKS!
I dripped a small amount into the hole, waited for it to work its way into the switch, and then pushed the switch several times to wipe the contacts and spread the solution. VOILA! No noise! Clean audio!
End of testimonial!
Seriously, if all else fails, get some of this stuff and try it. I think you’ll be happily surprised.
73 de Dick N4BC