Fluorescent to LED Conversion: Stealth Before & After




Introduction: Fluorescent to LED Conversion: Stealth Before & After

A hack shouldn't require any thought once it's in place, it should be easy. This is a true hack, because nothing appears to change, but "under the hood" there's a big difference. With this instructable, the after appears to be the same as the before, but the result is way more energy efficient with no change in behavior. Flip a switch and the light still turns on. It looks the same as it always did. But wait, it uses half the electricity it did before. Now that's a hack...

Problem 1: A fluorescent fixture that sometimes will not start, and flickers even with new tubes

Problem 2: Keep it simple! Don't change the way the fixture works or looks now

The Challenge: Keep the fixture compatible with "legacy" fluorescent technology and new LED options

Solution: Stealth before & after -- modern efficiency using new technology, but the casual user notices no change

I say "stealth" because this is indeed a significant transformation, with all changes transparent to the end user. The "before" was noisy, with replacement tubes that are becoming outdated. The after looks and functions exactly the same as far as my family is concerned, while supporting newer but still standard replacement tubes as well as cutting-edge plug-in LED replacements.

Background: Recently, one of the existing -- and aging -- fluorescent fixtures in our basement started flickering and would not fully light all the time. It uses 4-foot T12 tubes and a 40-year-old magnetic Class P ballast that has a familiar and annoying 60Hz hum when powered on. Replacing the tubes had no effect, therefore the ballast was the culprit. The T12 tubes are now outdated, replaced by more efficient T8 tubes that use the same connectors. Since I needed to replace the ballast anyway, why not use one that will work with the newer T8 tubes, too?

Coincidentally, LED lighting has become increasingly affordable over the past several years, along with a corresponding increase in quality and dependability. I have been replacing incandescent lamps throughout the house with LED lamps over the past year or so. And while fluorescent fixtures have always been more efficient than incandescent, the math doesn't lie: I could cut the energy usage by as much as 60% by updating the fixture to LED. I could also get rid of that nasty hum and use standard T8 tubes or new T8 replacement LED tubes in the same fixture. All I needed to do was replace the ballast. Fluorescent fixtures are mercifully modular and with a few common tools most anyone can handle this conversion.

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Step 1: Disclaimer! Alternating Current Is Potentially Dangerous!

Please understand that tinkering with AC power in your house could be hazardous. If you're not comfortable performing this on your own, please consult a licensed electrician. I show these steps for reference purposes only. Attempt this Instructable at your own risk...

Also, there are fixtures that hard "hard-wired" to an electrical circuit and those that plug in to an electrical receptacle. For fixtures wired directly to a circuit, please remember to open the circuit breaker before performing any steps like this Instructable discusses. I used a fixture with a plug, so I unplugged it from the wall first.

There, now that I've gotten that out of the way...

Step 2: Assess What You Have

There are a couple of important things to check to see if the process will be easy. The connector at the ends of the tubes are what you need to check. These bi-pin connectors are commonly referred to as "tombstone" connectors because of their shape. These have two different styles: shunted and non-shunted. For the work I am showing, we want non-shunted connectors. The primary difference is whether or not the 2 pins are electrically connected.

The type of fluorescent tube will also help identify the connector type. My fixture uses T12 tubes. This type of tube is pretty old and has been replaced by a newer, more efficient T8 size. The good news is both sizes will fit in a fixture designed for T12 tubes. The bad news is they're not always interchangeable because the ballast inside the fixture usually works for only one type of tube.

This Instructable shows installation of a fluorescent ballast that uses non-shunted tombstone connectors, and the connectors in my fixtures happened to be non-shunted. The fixture I show had an old ballast that used T12 tubes, while the new ballast only works for the T8 size.

Step 3: Never Fails, There's Always More Work Than You Thought...

The first time I tried this replacement, I worked on a ceiling fixture in my basement and it was clean and simple. Of course I didn't document that process. When I decided to document the process for an Instructable I used the plug-in fixture that had been out in the backyard shed for many years. It was beat up and really needed some remedial care. The pictures show you how much of a fire hazard it really was! It was a wonder it hadn't shorted out and burned down the shed long ago.

I pulled it apart, cleaned up the housing and repainted it. Big difference! Now I had a shell worth upgrading.

Step 4: Open the Fixture, Remove the Components

Fluorescent fixtures are usually extremely easy to service. They're designed to be opened up and dismantled, often without tools. My fixture requires only a screwdriver and a small socket to remove the ballast, the rest can be removed without tools.

Important: First things first: Either unplug the fixture, or find the circuit breaker to which the fixture is attached and open it to cut power from the fixture. Make sure the power is off to the fixture before proceeding.

  1. Open the fixture and remove the tubes.
  2. Look for a way to remove the service panel that covers the ballast and wiring. Some fixtures have wingnuts. Some have Screws. Remove the panel and set any fasteners aside for replacement.
  3. Disconnect the black (hot) and white (neutral) conductors form the ballast. It's likely that they're connected with wire nuts like this one.
  4. The tombstone connectors should be able to be removed.
  5. Remove the ballast fasteners and the ballast should come out easily.

Step 5: Install the New Parts

For reference, the ballast will likely have a wiring diagram printed right on the ballast itself. Follow the diagram and connect the different colors to the connectors. It's important to use the proper gauge of wire. 18AWG or 18-gauge is probably what the old ballast has in place. I believe most residential wiring codes require the use of solid core insulated wire.

These tombstone connectors are really easy to work with, and the connections are made by stripping the end of the conductor and pushing it into the hole. The wire pushes in but doesn't pull back out. There is a slot beside each hole where a small slotted screwdriver can be inserted to release the connector and allow the wire to be removed without having to open up the connector.

These connectors also allow for short conductors to be used as "jumpers" to complete the circuits described in the wiring diagram. Cut short lengths of wire, strip a bit of insulation from both ends and complete the connections according to the diagram. Pay close attention to which wires go where and where jumpers are needed.

I used the wiring from an old ballast for jumpers.

Leave the wires extended to full length at this point. Until the components are replaced, it's not clear how much slack there will be once the ballast is installed. after everything has been put back into the fixture, you can bundle the wires and make them neat.

Double-check your work and make sure everything is connected correctly. Now is the time to fix any mistakes while the wiring is accessible.

Step 6: Reassemble the Fixture

Now it's time to reverse the process. The new ballast is now connected to the tombstone connectors according to the wiring diagram.

  1. If you're working in a ceiling fixture, have a helper support the ballast while you replace the panels holding the connectors.
  2. Examine the way the ballast is secured to the fixture. It may simply use the same mounting hardware as the old one, but if it doesn't fit in the old mounting holes, drill a couple of small holes for sheet metal screws and fasten the ballast.
  3. Draw the wires together and neaten up the wiring paths to both ends. I used tie wraps to bundle them.
  4. Reconnect the hot and neutral conductors to the corresponding conductors on the ballast. Make sure the wire nuts (or whatever fastener you use) are secure. Don't forget the ground, too.
    Check your work one more time and make sure everything is installed correctly and neatly.
  5. Replace the service panel and carefully insert the new tubes.

Step 7: The Moment of Truth

Finally it's time to energize the fixture and see if everything works. If it's got a plug, plug it in. If it's hard-wired, close the circuit breaker. If it stays closed then there are no shorts in the wiring. If for some reason the breaker will not stay closed, there could be a problem with the wiring. Make sure the circuit is open and go back to check your work.

Caution: If there is any doubt, call a licensed electrician. Faulty wiring is always a bad thing!

  1. Make sure the circuit breaker is closed and the switch for the fixture is in the off position.
  2. Install the LED tubes.
  3. Turn on the switch and see how things look.
  4. Feel free to admire your handiwork!

Step 8: Conclusion: My Calculations

I have done some rough calculations, and while it seems a bit costly up front, in time the upgrade will indeed pay for itself.

The up-front cost per fixture is $35:

  • Each 4-ft T8 LED replacement tube is $10
  • The T8 ballast is $15
    • $10 x 2 + $15 = $35

The cost of Fluorescent lamps is about the same over the life of both types:

  • The lifespan for LED lamps is about 25,000 hours3hrs/day = 8,333 days, or more than 22 years
    • 2 lamps cost $20
  • The lifespan of a Fluorescent is rated at 20,000 hours but I've never had one last more than 4-5 years
    • 5 year lifespan for 2 lamps 10-pack of lamps cost $20

The new fixture uses about half the power of the old fixture:

  • Old: 60 watts
  • New: 30 watts

Some additional details regarding return on investment:

  • Assume 3 hours of usage a day, give or take
    • The annual cost savings is about $4.75
  • The return on the $15 investment of the new ballast is a little over 3 years
    • $15 / $4.75 = 3.16 years

In about 3 years the upgrade will pay for itself. That's a reasonable investment in my book. Plus, I had to replace the ballast anyway, so it looks like pure savings to me!

Step 9: The Parts and Tools I Used


  • GE Electronic Ballast ($15 at big orange store)
    • Product Code 93884
    • 120V
    • Drives 2 T8 lamps

LED lamp

  • Philips InstantFit T8 LED($10 each at big orange store)
    • Direct replacement for T8 fluorescent lamps
    • Non-dimmable
    • 4,000K color temperature -- "cool white"
    • 2,100 lumens

Tombstone connectors


  • White rust-resistant spray paint ($4.50 at local hardware store)


  • Wire cutters
  • Wire strippers
  • Socket set
  • Nut driver
  • Small screwdriver
  • Pliers


I spent a total of a couple of hours, including a trip to the hardware store to get the paint I didn't know I was going to need until I opened up the fixture. There was time in there to let the paint dry to the touch that I'm not including. I spent the afternoon working on the project, documenting it and getting it ready for this Instructable. I then spent a couple of hours writing, organizing and documenting the images with notes. It's really a never-ending process, since I'm finding things I missed the day before and small changes to clarify my thoughts.

It's a fun, satisfying project. I reclaimed a fixture otherwise destined for the scrap heap; I made it better than before while keeping it the same (if that makes any sense...); and I learned something. I call that a good day's work.

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    2 Discussions


    4 years ago

    Why do you need a ballast at all?

    Here in the UK the LED replacement tubes will run directly off our mains voltage (240v) they usually arrive with a drawing showing how they can be wired and yes they can be ran off a ballast using a special starter that basically shorts out the starter so that the voltage from the ballast is directly applied to the LED tube. However the tubes will work perfectly well without a ballast as they will run on 85-265 V AC and that is how mine are wired with 240 volts directly applied to one of the tube ends. As an early adopter the oldest ones have now been running for two years with no issues.

    I have taken the additional precaution of attaching a small label near the lampholders stating 'LED tubes only'

    You can find the LED tubes I am using here.


    Reply 4 years ago

    I considered that path. I chose this solution to allow for backward compatible fluorescent T8 lamps, as well. Even though I own my home, I always try to factor in resale value, and not everyone likes LED lighting.

    My primary requirements for the project were 1) keep the functionality exactly the same both before & after; and 2) support both legacy fluorescent and emerging LED.

    I really like your idea of a label for the type of lamp used. I have always simply replaced lamps with the same type, but one never knows who put the lamp in before you, and with these fluorescent fixtures supporting both T12 and T8, it makes sense to provide a message to the user about how the fixture is configured. Saves opening it up to see the actual inner workings.