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I am repairing my parents old single lamp (lamp F30T12-CW) ballast (old ballast was a GE 6G1075) with a two lamp ballast ( Phillips Advance B134SR120M-A) but only connecting one lamp The new ballast has 2 blue, 2 red, 2 yellow plus black hot and white common... what wires do I connect to the tombstones? Thank you

  • There is usually a diagram on the ballast that shows the different configurations. I would change over to T8 LED lamps. I use 3000 lumen lamps 20w. The ones I purchase are hybrids they can be direct wired single or double ended or work with the existing ballast. They fit in a T12 fixture and produce more visible or perceived light than the T12 and will last longer. – Ed Beal Sep 18 '19 at 13:19
  • The diagram on the ballast only shows a two lamp install.... there is a side note that says "For 1-lamp operation, individually insulate the yellow leads for 600v" Does that mean the two reds on one end and two blues on the other? – Rick Sep 18 '19 at 13:27
  • No put a wire nut on each yellow they are not being used. They want to make sure you don’t combine them that would short that section of The ballast out. – Ed Beal Sep 18 '19 at 13:48
  • So yellows are not used, so 2 reds on one end and two blues on the other? – Rick Sep 18 '19 at 13:59
  • That’s what individually insulate the yellows means. Most ballast are electronic (since ~2004) other than the yellows the diagram should be correct. – Ed Beal Sep 18 '19 at 18:50
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You don't, unless the ballast label or data sheet says you can.

In your case the ballast label says "For 1-lamp operation, individually insulate the yellow leads for 600V" - that is canonical. Further, it makes sense. They need to be capped off from each other because there is preheat voltage on them.

Since you need 4 wires and there are 4 wires left, do the obvious. The red wires go to the same end, because they provide lamp preheat for that end. That's what makes it a rapid-start ballast and not instant-start. Despite the names, rapid-start is better - it starts more reliably in the cold, and lamp life is much, much longer - because it starts the tube using its preheat feature as intended.

This does not mean you can do this 1-lamp trick for any rapid-start ballast. Many do not support it. You got lucky, don't chance it again - check the label or data sheet. Labels typically list some of the tubes supported; data sheets list every one.

  • My ballast says supports the bulb I have and can be used in a one lamp application. I am not an ignorant person but this is not my area of expertise... and I sure don't want to cause a problem/fire due to improper wiring in my 96 year old parents home. So please.... simply for me... if the yellow wire are to be capped off from each other and not used... are you saying 2 reds on one end and two blues on the other? – Rick Sep 18 '19 at 16:50
  • Yes, that's what it means. – Harper - Reinstate Monica Sep 18 '19 at 16:52
  • Thank you very much! – Rick Sep 18 '19 at 16:53
  • Installed ballast and everything works perfectly!!!! – Rick Sep 24 '19 at 13:42

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