Ditto what Jon S said... also be aware, that some Maggie models use a portion of the panel for a tweeter array... with a different grid of wires. Frequently, those tweeter grids will fail, even if everything else is working. Unfortunately, the grid wires are made of aluminum... and I really haven't seen many people able to get any of them working once the wiring fails. It's theoretically possible, to scrape away corrosion and/or sealing coatings, and use a conductive paint (like that used to fix auto rear window defrosters) to fix them, but I haven't seen anyone who was totally successful doing that...
Regards,
Gordon.