Oddly enough, most Nautel transmitters suffer horrible neglect. It's a rare operation, today, that pays any attention to preventive maintenance.
I know of one, of the ND generation, that suddenly fell silent.
When opened up, where there should have been a massive copper bus bar into which originally were mounted some huge diodes, there was only dust and some diodes dangling by their braided leads. The bar was gone - apparently vaporized! That'll happen when you don't snug things down every year or so.
When that missing piece got replace and everything was swept and vacuumed out it came back on the first try.
You can punish hell out of a Nautel AM transmitter and it'll forgive you if you give it the chance.
The one I tend has been in service (it's an ND-25) since 1996 with zero transmitter-caused down time. BUT, every cabinet and every module gets a close inspection, thorough cleaning and tightening once a year every year.