Tubes & Amp Parts for Hammond Organs and Leslie Speakers
Preamp, rectifier and output tubes for Hammond B-3, C-3, A-100 and M-3 organs and Leslie 122/147 amps, including AO-28 tube sets and matched 6550 pairs. Read the tubes & amp parts guide
Tubes & amp parts
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Tubes & amp parts: buying guide
Tubes are the first thing to check when a vintage organ sounds weak, noisy or distorted. This section covers single preamp and rectifier tubes, a complete AO-28 preamp set, and matched 6550 output pairs for Leslie amplifiers. Each listing says which chassis the tube fits, so you can order by the amp in your instrument rather than by guesswork.
The B-3, C-3 and A-100 consoles share the AO-28 preamp, which takes eight tubes: two 6AU6, one 12BH7, one 12AX7, two 6C4, one 12AU7 and a 6X4 rectifier. Our AO-28 tube set includes exactly that complement. The M-3 and M-100 spinets use the AO-29 amplifier instead, which uses 6AU6, 12AU7 and 12AX7 tubes along with a pair of 6V6GT output tubes and a 5U4GB rectifier. Leslie 122 and 147 amplifiers each run two 6550 output tubes, which we sell as matched pairs.
When you replace tubes, swap one at a time and note which socket each came from. With the organ on and the volume low, a gentle tap on each tube will usually reveal a microphonic or noisy one. If new tubes don't cure hum, the capacitors are the next suspect; see our recap kits.
Common questions
What tubes does a Hammond B-3 use?
The B-3 shares the AO-28 preamp with the C-3 and A-100. It takes two 6AU6, one 12BH7, one 12AX7, two 6C4, one 12AU7 and a 6X4 rectifier, eight tubes in all. Our AO-28 tube set contains that full complement, or you can replace single tubes as needed.
Which output tubes does a Leslie 122 or 147 use?
Both amplifiers use two 6550 output tubes in a 40-watt push-pull stage. Replace them as a matched pair so both tubes share the load evenly. The 122 and 147 differ in their input and speed-switching circuits, not in their output tubes.
Are the AO-29 tubes the same as the AO-28 tubes?
Some types overlap, such as the 6AU6, 12AU7 and 12AX7, but the AO-29 in the M-3 and M-100 is a combined preamp and power amp. It adds two 6V6GT output tubes and a 5U4GB rectifier, so check the tube type printed on the socket chart before ordering.
How can I tell which tube is bad?
Start with tubes that don't glow, then tap each tube gently with the organ on and the volume low; a crackle or ring points to the culprit. Swapping one tube at a time with a known-good spare is the most reliable home test.