Yes as you said I do not know how to tell if it is operating properly, which I stated in the listing...the most I can verify is sound comes out, knobs move and the sound is different, lol. I have found someone local that said they can diagnose and fix when I receive it back. I am now gun shy on sell...

I have a realistic mg-1, I sold it on eBay and it is being returned, the buyer said the detune slider did not work and there was intermittent sound when changing functions. I know zero about these units. I did read there is some foam deterioration issue, would it be any help if I cleaned the inside?...