I am having a similar issue.
It started out with a bad lamp transformer. None of the oven lamps lit. I replaced the transformer, then only the lower oven would work.
I then replaced the main power board only. The panel was dim for the top oven and fine for the lower. I assumed the resistor included on the new board caused this. As the oven was used, the panel got dimmer to the point of being unreadable. The lamps don’t work again now either.