Hammond Chord Organ Tube Chart

The Hammond Chord Organ changed relatively little as it went through Models S, S-1, S-4, and S-6. Tube-wise, the biggest change was that the 6SN7 tubes in the original Model S became 12AU7s in the S-1 and subsequent models. Tube V1 changed function slightly, and became a 6C4 in Model S-4. Finally, Model S-6 added a new tube, V30, a 6BJ7.

The Owner's Service Suggestions for the Hammond Chord Organ on this site was written for the original Model S, and so refers to 6SN7s, 6SK7s, and so on. The tube numbers and the function of each tube didn't change, and the layout of the chassis remained basically the same. The basic procedure is to take tube 12 (V12) as a spare, and work your way through all the similar tubes (6SN7s or 12AU7s) to identify a bad tube. Not all the substitutions for a Model S are the same in the later models, since three of the 6SN7 tubes became 12BH7 in Model S-1 and later models. Also, tube V1 ended up as a 6C4 in models S-4 and S-6.

Tubes by number

Tube	Function	S	S-1	S-4	S-6
V1	Solo Oscillator (and Chord Control in S, S-1)	6SN7	12AU7	6C4	6C4
V2	Solo Oscillator and Vibrato Oscillator	6SL7	12AX7	12AX7	12AX7
V3	Solo Oscillator Rectifier and 1st Divider Driver	6SN7	12AU7	12AU7	12AU7
V4	Solo 1st Frequency Divider	6SN7	12AU7	12AU7	12AU7
V5	Solo 2nd Divider Driver and Vibrato Switch	6SN7	12AU7	12AU7	12AU7
V6	Solo 2nd Frequency Divider	6SN7	12AU7	12AU7	12AU7
V7	Solo Bass Rectifier and Pedal Limiter	6SN7	12AU7	12AU7	12AU7
V8	Solo Preamplifier and Pedal Control Tube	6SN7	12AU7	12AU7	12AU7
V9-V10	Solo Control	6SK7	6BA6	6BA6	6BA6
V11	Power Rectifier	5U4	5U4	5U4	5U4
V12-V19	Organ Oscillators	6SN7	12AU7	12AU7	12AU7
V20	Amplifier and Preamplifier	6SN7	12AU7	12AU7	12AU7
V21-V23	Chord Oscillators	6SN7	12BH7	12BH7	12BH7
V24	Pedal 1st and 2nd Divider Drivers	6SN7	12AU7	12AU7	12AU7
V25	Pedal 1st Frequency Divider	6SN7	12AU7	12AU7	12AU7
V26	Pedal 2nd Frequency Divider	6SN7	12AU7	12AU7	12AU7
V27	Phase Inverter	6SC7	12AX7	12AX7	12AX7
V28-V29	Output Tubes	6V6	6V6	6V6	6V6
V30	Percussion Rectifier	-	-	-	6BJ7

Tube Counts by Model

As this table shows, most of the 6SN7s in the Model S become 12AU7s in Model S-1 and later models. Three of the original 6SN7s ended up as 12BH7s in later models. One of the 12AU7s (V1) became an 6C4 in models S-4 and S-6.

The 6SK7s (V9 and V10) in the Model S were replaced by 6BA6s in later models.

Two tube types used in the Model S, 6SL7 (V2) and 6SC7 (V27), ended up as type 12AX7 in later models.

Tube V30, an 6BJ7 was added in Model S-6.

Model S		Model S-1		Model S-4		Model S-6
tube	count	tube	count	tube	count	tube	count
6SN7	22	12AU7	19	12AU7	18	12AU7	18
-	-	12BH7	3	12BH7	3	12BH7	3
-	-	-	-	6C4	1	6C4	1
6SK7	2	6BA6	2	6BA6	2	6BA6	2
6SL7	1	-	-	-	-	-	-
6SC7	1	-	-	-	-	-	-
-	-	12AX7	2	12AX7	2	12AX7	2
6V6	2	6V6	2	6V6	2	6V6	2
-	-	-	-	-	-	6BJ7	1
5U4	1	5U4	1	5U4	1	5U4	1
total	29		29		29		30