Ventilation fan blew on one of our ETC "Sensor" packs during the ballet. Stood a box fan up next to the dimmer pack to keep it going.
The fan is inset too deeply to be able to read the data plate, and I didn't want to go through the process of cracking the case unless I knew a replacement was available. I mean, it looked like a standard 4" muffin fan, but engineers sometimes get creative and it might be some one-of-a-kind 33.3 volt multispeed fan with an ambifacent lunar waneshaft and twin spurving bearings.
So we contacted ETC for the correct part number, found it at an online dealer, and when the part arrived I opened the case. And then and only then noticed we'd managed to order a 10" fan.
Well, fortunately, now that the case was open I could read the nameplate, and it did turn out to be a common design and an essentially similar recommended replacement was available at the nearest Grainger.
"Nearest" being down the freeway, since they consolidated (and closed the local store). Spent the morning driving down to get the part, wriggled it in, wrestled the pack back up to the racks, and it works fine. But during the drive, the engine fan on my car blew, so now I have to deal with that!