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I'm wanting to do a ballast bypass in this ancient fluorescent fixture with a magnetic ballast in my laundry closet. It has a single bulb and is easy to access, so I thought it would be a good one to try out the bypass on to see how it goes. When i opened the fixture up, I noticed something I hadn't seen before in the how-to videos. One tombstone has three wires coming out of it. There is a blue from one side of the tombstone directly connected to the ballast, then on the other side of the tombstone are two white wires: one directly connected to the ballast and one wired to the neutral from the house. Is it ok to just combine all three (the two whites and the blue) to the house neutral or do I need to pull one out or what? The picture shows the three wires coming from the one tombstone. The tombstone on the other side has two red wires directly connected to the ballast and looks as expected.

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2 Answers 2

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It doesn't matter if the wires are paisley :)

All wires which go to one tombstone are connected to utility "hot".

All wires which go to the other tombstone are connected to utility "neutral".

That's that. You are now ready for a double-ended ballast-bypass LED, or a universal LED.

If you somehow get a single-ended ballast-bypass LED, or a Plug-n-Play LED, or a Type C, then send it back.

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  • Thanks. That's what I figured, it was just odd to me that one of the white wires was going directly from the ballast to the tombstone, then the other one next to it on the same side of the unshunted tombstone was going to the neutral of the house. It's as if the ballast is using the tombstone as a connecting point to get to the house neutral, instead of being directly wired to it. Made me wonder if those white wires should even be part of the equation if there is no ballast anymore.
    – Nick
    Nov 19, 2023 at 20:44
  • @Nick yeah there's a reason they do it, the simpler ballasts sometimes put themselves partially in series with the line voltage. But they still need power for their own stuff, preheaters, etc. Nov 19, 2023 at 23:32
  • I see. So it's ok if I leave those lines in the tombstone and connect them to the house neutral from there?
    – Nick
    Nov 19, 2023 at 23:52
  • @Nick my only concern is the neutral might need to go to both pins on the tombstone. I suppose you could connect the other two to each other. Nov 19, 2023 at 23:57
  • The tombstone with the two white wires on its right side has one blue wire on its left side, as shown in the picture. So three wires total. Do I combine all of those and then connect them to the house neutral? I'm not quite sure what you mean by "connect the other two to each other." The tombstone on the other side of the fixture has two red wires coming out of it, as you'd expect. I really appreciate the help.
    – Nick
    Nov 20, 2023 at 0:29
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Probably. It depends on what the ballast bypass lamp expects. The ones I've used need line on one end, neutral on the other. In that case you can treat all three of these wires as the same wire and put them in a wire nut with line or neutral, then do the same with the two wires at the other end.

Make sure to install the sticker which shows the ballast has been bypassed.

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  • That was my plan, to get an LED powered from both ends that works in a fixture with the ballast bypassed. The thing I'm wondering about is what to do with those white wires running from the socket, because I've never seen that before. I've only ever seen blues, reds, yellows coming from the sockets, not what I assume are neutrals. I know that a proper replacement ballast for this model would require taking out both the whites and putting one blue from the ballast in their place, so just putting a blue in their place is an option for a bypass, but I'd rather avoid that struggle if possible.
    – Nick
    Nov 19, 2023 at 16:12
  • Don't get hung up on the colors. This is for a preheat style fixture I think. White, white, and blue from that end go all together to neutral. All the wires from the other end go to line. Done.
    – KMJ
    Nov 20, 2023 at 6:46
  • Yep. It's about 35 years old. Same age as the home. According to whats on the ballast it's a rapid start, and I could not find any starter for it so I assume that's right.
    – Nick
    Nov 20, 2023 at 14:11

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