So this evening, I had the most catastrophic ballast failure I’ve ever had. Up to this point, the most I’ve ever had happen for exciting failures is with HID ballasts. I’ve had cores go up in smoke, and capacitors turn into pressure cooker smoke machines. I’ve never had anything crazy happen with fluorescent ballasts… usually they just refuse to work or they underdrive the lamps like crazy.

Tonight, I decided to embark on a multi-year procrastinated project of converting some old 50s-60s F40T12 Single Lamp strips to Preheat. These fixtures are originally rapidly start, and have big old GE HPF ballasts dating from the mid 50s. Powering them up, they work very well, drive the lamps HARD at like 55w, and have an incredible power factor of .95. I would normally keep a fixture like this original, but these fixtures have blatant knockouts intended for starter sockets. Would be rude not to convert them to Preheat, so I did just that tonight.

I was originally going to use some 1972 CGE NPF Preheat ballasts, but they aren’t cosmetically in great shape. So, I decided to experiment with using the original Rapid Start ballasts as Preheat. This was achieved by disconnecting one of the two blue leads to one socket; and disconnecting the neutral bridge on the opposite socket. So, you had one blue line on one side, the green line on the other, and a starter wired between the open pins on each side. The white and black lines went straight to the mains.

This worked very well, better than the NPF CGE ballasts I had. The lamps operated perfectly and started up very quick. Power factor still good, and excellent drive to the lamps. All stats on the meter matched how it ran on rapid start. Awesome. So I proceeded to convert the other two in the same way. They both worked great as well.

It was about an hour after I finished the first one and let it sit running off to the side, that I start to hear what almost sounded like rain outside. Not thinking about it much I carried on with whatever I was doing. A few minutes later I start to hear it get louder, then I look over to see white smoke POURING out of that fixture followed by arcing sounds! S##T! Ripped the cord out of the wall and took the fixture outside.

There was oil EVERYWHERE and it stunk. It got all over the garage floor and the inside of the fixture. The next hour was followed by me gutting the fixture, tossing the ballast, and trying to get this godforsaken substance off every surface it was on. I got the majority cleaned, but any object that has even just a microscopic amount of it stinks horribly. It’s most definitely PCB oil too, which makes this all the more a big problem. I can seriously still somehow taste it and smell it on my hands DESPITE me wearing gloves through the whole process and thoroughly washing my hands afterwards.

So now I’m stuck trying to think what the heck actually happened here. The only thing I can think of is that I should have capped the green wire and wired the lamp directly to neutral like in the diagram… though I’m not sure if that would really have had any effect on operation. Interestingly enough, the other two fixtures were running perfectly fine, even after that one blew up. The working ballasts were warm but not alarmingly so. The ballast that blew up was scorching hot. It was running just fine though for over an hour before this too. I just can’t imagine that the way I wired this would cause such a spectacular failure, but I could be wrong.

So I guess I’m just gonna use the 70s NPF ballasts after all. Oh well. Would be curious to hear from others on this. I still can’t conclude whether it was me that caused it, or if it was just doomed from the start. Picture of the ballast label below.