I'm not familiar with the 8663A, but I did have a problem once on my 8780A where the keypad didn't respond.? The problem turned out to be a broken copper leaf spring underneath the "8" key.? The key contact was being shorted closed and to the instrument, it appeared that the "8" key was always being depressed.? To the user, the entire instrument keyboard appeared as non-responsive.
After I figured out the problem, I realized why a single "8" always appeared on the display after the instrument powered up.? Doooohhh! :-)?
