T12 Ballasts – Electronic & Magnetic Fluorescent Replacements

What These Ballasts Replace

• F40T12 / F34T12 — 4 ft shop lights, offices, schools, retail strips. 1-lamp and 2-lamp rapid start, usually 120V.
• F20T12 — 2 ft T12. Same family, lower wattage.
• F96T12 / F96T12HO — 8 ft industrial and high-output. Instant start or rapid start, often 120–277V.
• T12HO sign lamps — Multi-lamp sign ballasts that also cover T8HO sign tubes. Not a general office T8 ballast.

Parent: Fluorescent Ballasts · Sibling: T8 Ballasts

T12 vs T8 — do not mix

A T8 fluorescent tube on a T12 ballast is overdriven. Replace this ballast with another T12 unit, convert the fixture to a T8 ballast plus T8 lamps, or bypass the ballast and install a Type B LED tube.

How to Choose

1. Read the lamp stamp

F40T12, F34T12, F20T12, F96T12, or F96T12/HO. HO and slimline 8 ft units are not interchangeable with a 4 ft F40 ballast.

2. Match lamp count

1-lamp or 2-lamp for linear fixtures. Sign ballasts are listed as 4–6 lamp and a length range, not a single F40.

3. Start method and voltage

• Rapid start — most 4 ft T12 replacements
• Instant start — many 8 ft F96 units
• 120V or 120–277V universal

4. Keep T12 or leave fluorescent

Keep T12 when you only need the fixture back on today. Convert when the ballast is a repeat failure: T8 lamps + T8 ballast, or Type B LED tubes with the ballast removed.

Why Buy from LeanLight?

• Fast, free shipping from Georgia
• Keystone, LEDVANCE/Sylvania, and Halco cross-references
• Volume pricing on cases
• 30-day satisfaction guarantee

Related: Fluorescent Ballasts · T8 Ballasts · LED Tubes · Linear Fluorescent Lamps

Frequently Asked Questions

What does a T12 ballast do?

It strikes the T12 lamp and then limits current. Without it the tube would draw unlimited current and fail.

Can I replace a magnetic T12 ballast with electronic?

Yes, if lamp type, lamp count, voltage, and case size match. Confirm tombstone wiring if you later convert to instant-start T8 or Type B LED.

Can I put a T8 tube on this ballast?

No. Buy a T8 ballast for T8 fluorescent lamps, or a Type B LED tube and disconnect this ballast.

F40 vs F96 — same ballast?

No. F40 is 4 ft. F96 is 8 ft. Use the ballast listed for the lamp on the fixture.