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Percussion Keying Modification

The Hammond percussion effect is produced by borrowing the second or third harmonic signal from the corresponding manual drawbar, amplifying it, and returning part of the signal to the same drawbar. At the factory, the 1’ (9th) drawbar is used to key this effect, rendering that drawbar inactive when the percussion effect is switched on. A popular modification involves selecting another drawbar, typically the 1 3/5’ (7th) or 1 1/3’ (8th), to key the effect, thereby reactivating the 1’ for use with percussion. This is easily accomplished.

Looking into the back of the organ, locate the small 6 lug terminal strip attached to the manual chassis near the middle of the organ. Each lug has two wire attachment points. As you look in from the back of the organ, the lug on the far left has two white wires attached: the top wire goes to the percussion switch and the bottom to the 1’ drawbar. Complete these steps to change the percussion keying:

1. Remove the white wire from the 1’ drawbar for the upper manual B preset; let it dangle for now.

2. Remove the lower white wire attached to the far left lug of the terminal strip described above. Reconnect this wire to the 1’ drawbar from which the white wire was just removed. You might need to splice in some extra wire to provide enough length.

3. Disconnect the wire from the drawbar of the desired harmonic and connect it to the terminal strip where you just removed the white wire.

4. Finally, connect the dangling white wire from Step 1 to the drawbar where the wire was just disconnected in Step 3. That’s it – enjoy!

Tips and Techniques Archive

Here are links to some previous offerings that you may find of interest...

May 2008 - Getting the most from your 1122 Leslie kit

January 2009 - Bad Scanner? Maybe Not...

Getting The Most From Your 1122 Leslie Kit
If your own a Hammond XK-3 or any other keyboard with an 11 pin Leslie out, you can connect to a 142 or 122 Leslie using the Hammond 1122 Leslie kit. Better still, the 1122 kit can be easily modified at the Hammond Clinic to work perfectly with the EIS Mark II relay. This means you can now have full control over the Leslie motors, including fast, slow and stop. It even works with demos on the XK series organs! And don't worry if you happen to encounter a Leslie 122 amp without an EIS relay -- you still retain preamp functionality with older generation relays. Call for details if this interests you. Sorry -- this modification is not available for the 1147 kit at this time.

Bad Scanner? Maybe Not...
Over the years, we have worked on quite a few vibrato problems that would appear to be a scanner issue but, in fact, were not. There are several things that can mimic a bad scanner. Some of them are:

1. a weak 6AU6 tube
2. a weak 12BH7 tube
3. a shorted cap in the vibrato line box
4. "stretched" plate, or screen resistors
5. growth in the vibrato selector switch
6. one or more broken wires in the wiring harness just below the percussion switches

Before you spend good money rebuilding a scanner, it is a good idea to check the points mentioned above.