If it's a LED display and all the lights are dim, I think it might be an issue with the power supplied to the LEDs. Maybe it's a constant current source going bad.
I took the cover off intending to do some voltage measurements, but the board in question isn't readily accessible, plus (even in 2001) it's all the very smallest surface mount stuff. So unlikely I could either find the problem or fix it, or keep from messing up the glued-on ribbon cable to the display in the process. So I just put the cover back on.
But now, when the door is closed and the oven isn't doing anything, the display is pretty bright! If I open the door, or start it cooking, it goes dim. As you say, looks like a power issue. So clearly I need to go back in and remake all the connectors. And that would include the fuse holders. Anything else? Anyway, I may very well owe Sharp an apology.