That's a bummer. I own two R8600's and never had a display issue with either except once when I accidentally let some LCD touch screen cleaner and anti-static spray get below the front bezel from me spraying too much on the cleaning towel I was using! I didn't realize I'd applied so much cleaner onto the towel that I could have wrung liquid from it!
The screen stopped responding to touch until I dried it out with a fan. Never another problem since that mistake.
Do the LED's on your front panel still light up when the LCD screen goes dark?
I wonder if someone could walk you through the menu button press's needed to get to the reset screen where you could try and perform a total reset even though you can't see anything. I don't know if that would work and it definitely won't work if your screen is also not responding to any touch input. I don''t think there's another way to do a factory default reset without using the touch screen for parts of the reset procedure.
You did not accidentally hold the P.Lock button in for a couple seconds did you? That blanks the display but that button should turn on a white LED on the left side of that button if you did that.
If that button has the white LED lit, hit the button again to bring the display back. With that lit though, the other controls should also not work so I doubt it's that simple.
Good luck with it and hopefully it will be something very simple.
Oh, did you try it with no SD card at all? I know you tried a different card but in reality, no card is needed to operate the 8600.
I assume you are also removing all power sources for several minutes as well. Maybe pull the power while the radio is on which should help drain any caps quickly.
I already miss my 8600.
