Here is the story of my Hammond BV organ Trek II percussion unit conversion in pictures. Click on any photo to see it in high resolution. I hope this helps someone. Email me at the address below if you have any questions or comments.

Here's the conversion kit laid out for inspection

The first task is to remove the wood music stand and top keyboard manual cover (two small screws), then remove the large bolts holding the top manual in place from underneath the organ. You need to raise the top manual up at the left hand end using something like wood blocks. Be careful not to damage any keys in the process.

The reason you need to raise the keyboard up like this is so you can get to the screws that hold the wood end block in place. These are screwed in from underneath. You will need a stubby or offset screwdriver to get these out.

Once you have removed the the wood end block and screws, squirrel them away safely in case you ever want to restore the organ back to original.

The two screws are replaced with two T-nuts, then the metal chassis for the Trek II unit can be fitted in place of the wood end block. The chassis is bolted down from above.

The Trek II printed circuit board with trailing wires can then be fitted. The wires need to be routed to the rear of the organ. I found it easier to remove a small square of the felt material in order to route the wires neatly with the prospect of them getting damaged. Once the wires are routed, the PCB can be bolted into place using the supplied standoffs.

Then the top cover and knobs can be installed - it looks very neat. Don't mind the dust on my preset keys - the cleaner isn't allowed to touch my BV and I hadn't cleaned for a while. Next step is to re-assemble the keyboard - simply a reversal of the disassembly process.

Then you need to wire the unit up from the rear of the organ. The black wire goes to the GND busbar. Note, in this picture, you can see the other new wires from my Smooth Drawbars conversion.

Then the wires to the appropriate drawbars are unsoldered and connected to the appropriate wires from the Trek II unit using the supplied wire nuts. Follow the Trek II instructions explicitly here to ensure the correct harmonics are chosen.

Then the audio feed needs to be connected to the pedal resistance box (or expression unit, depending on which Hammond you own). Here's the box opened up, with before and after photos. It's not obvious how this wire should be connected from the Trek II instructions, so be careful.

Then the power supply transformer needs to be wired up. The Trek II kit provides a clamp-on AC connector for this, but I decided I preferred to wire the transformer into the power strip on the the organ's pre-amp directly. Mount the transformer well away from the pre-amp and any audio wires - you wouldn't want to introduce any hum! You can see my Hamilton Leslie 122 control conversion installation in these photos also.

That's it, all done. Put the organ cover back on and test the percussion unit. I think you'll be very pleased with the results.