Percussion Volume Drop M3

Make Sure you've seen EliminatingThePercussionVolumeDrop to know what this mod does!

The pictures below show a Hammond M3 (Serial#: 60860)

First you need to get at the matching transformer. Its inside the aluminum enclosure under the lower manual drawbars, above the tone wheel cover on the right.

Remove the two screws on the mounting brackets and carefully move the drawbar leads away from the enclosure. Then remove the two screws securing the cover, and remove the cover.

Notice a pair of 1 Meg resistors mounted on a strip on the left side of the matching transformers. The resistor to jumper out is the lowest one when the matching transformer is mounted (R2 (1Meg)). Make sure you use a clip-lead to jumper R2 first as a test.

To test what the jumper change will do before you solder it permanently, turn the percussion ON with the first 4 drawbars out to position 8. Hold a chord, listen for the percussion to decay, then while still holding the chord, rock the Percussion volume (not organ volume) tab from SOFT to NORMAL. Notice that the drawbar volume drops! This is normal in all organs of this type and is considered a serious drawback by many professional players. Most play the organ with the percussion tabs "four up" or all four tabs rocked up toward the rear of the organ for this very reason. This mod to eliminate the organ volume drop completely changes the way the organist can use the percussion!

Once you understand the original percussion situation, try this - add the jumper on the lowest resistor on the left, then hold a chord with the percussion on SOFT, let the percussion decay and while still holding the chord, rock the Percussion tab to NORMAL. You should now not have a drop in drawbar volume when you switch the percussion volume tab from SOFT to NORMAL.

R2 Has been clipped off leaving some lead to solder too.

• This resistor doesn't need to be clipped out. It would disappear to the circuit when jumped, and the mod could more easily be reversed. It might also be easier for someone else to find using the schematic. I'm using ground bus wire since it's going to ground anyway, and it's easier to work with than insulated wire. Thanks for the great mod and pics. -towlie

Jumper soldered in place.

TopicModification