When replacing or upgrading the tombstones (socket components) in a T8 tube light fixture, it’s important to understand how to properly handle the installation and what types of components are available. This guide will take you through the process of changing out the tombstones and explain key differences between shunted and non-shunted tombstones, as well as the different types of bulbs (Type A and Type B) that can be used with these fixtures.

What You'll Need

- Replacement tombstones (shunted or non-shunted) 
- Type A or Type B T8 LED bulbs (depending on your fixture and preference) 
- Screwdriver 
- Voltage tester 
- Wire cutters/strippers 
- Electrical tape (optional)

Step-by-Step Guide:

1. Turn Off the Power

Safety is always the priority. Make sure to turn off the power at the circuit breaker to the light fixture before working with any electrical components. Double-check with a voltage tester to ensure there is no power running to the fixture.

2. Remove the Old T8 Bulb

If you're replacing an old T8 bulb, gently remove it from the tombstones by rotating it and pulling it out of the sockets. If the bulb is broken, wear gloves to avoid injury from glass shards.

3. Identify the Tombstones 

Tombstones are the small socket components that hold the T8 tube light in place. There are two main types of tombstones:

• Shunted Tombstones: These tombstones have a built-in electrical connection between the two terminals. This means power is sent to both pins of the bulb simultaneously. These are typically used with ballasted fixtures (e.g., older fluorescent setups) where the ballast controls the power flow.
  

• Non-Shunted Tombstones: These tombstones have no electrical connection between the terminals. Each terminal is independently wired to different parts of the circuit. Non-shunted tombstones are used when bypassing the ballast (common in LED retrofits).

4. Remove the Old Tombstones

 
Be sure to make note of how the wires are connected, as you'll need to replicate the wiring for the new tombstones.

5. Install the New Tombstones

For non-shunted tombstones, connect the wires from the fixture to the appropriate terminals on the new tombstone. Usually, the wires will connect to two separate terminals — one for the live (hot) wire and one for the neutral wire. Tighten the screws to secure the wires in place. 
 
For shunted tombstones, follow the same procedure, but remember the two terminals are already electrically connected, so you don’t need to worry about independent wiring. 
 
Once the wires are connected, secure the tombstone in place using the screws or clips.

6. Install the New Bulb 

• Type A Bulbs (Plug-and-Play): If you’re using a Type A bulb, which is compatible with the existing ballast, simply insert the bulb into the tombstone sockets. Type A bulbs do not require you to bypass the ballast, so they should work with shunted tombstones.
• Type B Bulbs (Ballast Bypass): If you are using a Type B bulb, ensure that the ballast has been removed or bypassed, and that the tombstones are non-shunted. Insert the Type B bulb directly into the non-shunted tombstones, making sure it fits securely.

7. Test the Fixture

Once the tombstones and bulbs are installed, turn the power back on at the breaker and test the fixture. The light should power on immediately. If it doesn’t, double-check the connections, and make sure the bulbs are properly seated in the tombstones.

8. Troubleshooting

If the light is still not working: 

• Check for any loose connections at the tombstones. 
• Verify that the correct bulb type was used for the given setup (Type A or Type B). 
• Ensure that the power is on and that no fuses or breakers have been tripped.

Types of Bulbs: Type A vs. Type B

Type A LED Bulbs These are compatible with the existing ballast in the fixture and do not require any rewiring. They're often used for a simple retrofit and are called “plug-and-play” bulbs because they work immediately after installation. 
 
Type B LED Bulbs: These bulbs require a ballast bypass, which means the ballast must be removed or disconnected from the circuit. Type B bulbs are more energy-efficient and provide longer-lasting illumination, but the rewiring process can be more involved.

Now You Know

Changing the tombstones in your T8 fixture is a straightforward process once you understand the different components involved. Be sure to choose the appropriate type of tombstone based on whether you're using Type A or Type B bulbs, and follow safety protocols when working with electrical components. 
 
If you're upgrading from fluorescent tubes to LED, replacing the tombstones with non-shunted ones and bypassing the ballast can improve energy efficiency, as Type B bulbs don't rely on a ballast for operation. However, for simpler, plug-and-play installations, Type A bulbs and shunted tombstones are the way to go.