Hello, my name is***** to Justanswer! Give me just a few minutes to look up some specifics, I'm working on this now.
Do you still need help with this?*This is not your answer, just an inquiry to see if you still need help. I'm here to help when you're ready. Due to the nature of the problem, it may take a few tries back and forth before we finish the troubleshooting and fix the problem.
If it's the backlight that isn't working, you can shine a flashlight into the display, and you'll see the characters. Since it's blue, try that first to find out. I think you'll find that a ribbon cable was not seated properly during the replacement, unless you see characters with a flashlight. If you do, change the backlight.
Deoxit is the stuff to use, but sometimes the ribbon doesn't always align properly. They are a pain. Yes, the LED is the backlight for the whole screen.
The other thing that can go out is the IC that sends the characters to the screen. If that goes bad, you'll need to replace the module that the LCD plugs into.
That's getting a little above my pay grade... Basically if you are sure the contacts are lining up on the ribbon, on both ends, and it still doesn't work, and you are certain that the LCD works, then the IC is dead.
You did read the part about the IC that sends the characters to the LCD, correct? When there are no characters, and the rest of the machine works, it's either the LCD or the IC that needs replacement. The IC you would have to order from Korg.
Sounds good, you're on the right track.