I remember in the early stages of my electrical apprenticeship working on troffers with the old PCB ballasts.
I seem to remember how nice it was that the manufacturers (Thorn, I think) rivetted the ballasts to the top of the troffer body.
One morning I was working in the editorial office of our local newspaper, removing these ballasts and replacing them with wire-wound ballasts.
The first person into the office that morning turned on all the lights, so that when I turned up, the ballasts were too hot to touch, let alone hold while you drilled the rivets out.
One other thing I remember too, was that the wiring they used inside the troffers had a habit of having it's insulation go brittle, due to the heat inside the fitting.
I only had to be taught that lesson once, as the place had to have as many lights on as possible as the staff were proof-reading and checking colours and what-not as I worked.
For a split second, they had all the light they needed, when I took the cover off one of the troffers.
The insulation fell off all of the wires and shorted to the troffer case.