WARNING !!!
Before we even begin a description of the X66, it is, I feel, of paramount importance that I should warn all owners and players of X66 Hammond organs of a dangerous electrical condition which now is very likely to exist in your instrument. Within the last 2 years, I have worked on seven different X66 instruments, and I have encountered this problem in all of them.
Considering that I have seen this in seven out of 7 instruments, it is logical to conclude that this problem may be much more widespread than any of us might realize. The problem concerns the AC power wiring within the console that supplies the pedal lights and also the vibrato and celester drive motor. In all of the instruments that I encountered, the insulation on this wiring has now become dried out, hard and brittle and in many places it has broken off, leaving bare wires carrying 120 volt AC power. In our NSHOS club instrument, the problem showed up as a persistent 120 cycle (second harmonic of the AC power frequency) humming and a buzzing in the speakers, with the buzzing being particularly prominent in the Leslie. The second and worse problem was that if you touched any part of the metal on the console, and also anything else electrical such as a microphone, you would get a nasty shock.
When we examined the instrument, we found significant portions of this wiring which was bare and part of it was touching the inside of one of the two main support columns. The support columns are attached to the metal framework in the bass pedestal and from there, AC power would be present on any of the rest of the metal in the console. We could not connect any auxiliary equipment to the console as a result, and had to warn all of our guest artists against touching anything metal on the console. After we replaced this wiring, all of these problems went away. The instrument no longer produces 120 Hz humming and buzzing over the speakers, and it is safe to touch it and likewise to connect auxiliary equipment such as signal processors or recording equipment.
I have likewise found this problem on the X66 here at the house, on three instruments that belonged to our club VP, Jim Gregory, and also in one which was shipped to Europe. It therefore is logical to conclude that this problem is widespread among the X66 models, as they are all approximately the same age now within a few years, and it seems that the AC power wiring for the pedal lights and the scanner motor, which was actually a lampcord variant that Hammond used, has inferior insulation. Doubtless it was good wire in its time, but this is over 5 decades later and now it is a dangerous problem.
I cannot stress strongly enough that if you own or regularly use an X66 Hammond, that you should either check this yourself, or find a qualified Hammond repair technician who can check this wiring for you and replace it if necessary. If your instrument has its original wiring for the pedal lights and the scanner drive motor, you may have a potentially serious and dangerous electrical hazard on your hands which should be addressed right away. In my work on these six different X66s, I have not found any other wiring in any of the consoles which has degraded, so it seems that the lampcord that Hammond used for these two applications has insulation of a different type from that of the remainder of the wiring.
My best advice is simply this. Get this checked right away, DO NOT USE the instrument without verifying that this wiring is OK, or if defective, replaced ASAP.