See also David Webster’s guide to installing a triple jack socket here 

This modification invented by Jack Lyon (and Organ-Den?) adds a dedicated TRS (6.3mm) jack for connecting a “Leslie slow/fast” foot switch (pedal) on the rear side of the VR

With this jack the damper and expression in-jacks are free for other things, e.g. permanently connected expression pedal + piano damper pedal

The mod is quite easy and requires only very basic soldering skills. If you have zero experience with soldering you for sure know somebody who has and is willing to help you.
When soldering or touching the electronic boards take care that your body does not carry static electric charge. De-charge yourself by touching the ‘ground’ pin of an electric wall socket. Don’t wear wool or fleece cloths

You need:

• a piece of cable (e.g. from an old broken headphone..)
• a TRS (6.3mm) mono jack (e.g. Adam Hall 7203 TP PCB02 : Thomann/Europe, 3 euros for 2 pieces)
• a screwdriver for opening the VR
• a soldering iron (ca 30 Watt)
• something to drill a hole : a small drilling machine or a Drehmel

You have to:

• put the VR top down
• undo all screws on the bottom side: open the VR09 / VR730 as described here Open VR09 or here: Open VR730. Don’t forget to unplug the battery cable when lifting the bottom off
• search a free place on the rear panel of the housing where you want to install the jack (see photos below)
• drill a hole: do it carefully, starting with a small drill, then increase diameter. Or use a Drehmel
• cut the cable to the correct length (see photo below). Undo isolation
• solder the cable to the jack. Do this outside of the VR housing to avoid dropping solder onto the electrical boards
• now insert the jack, fix it with the nut
• place the cable e.g. as shown in the photos
• carefully solder the cable to the pins of the ‘rotary fast/slow switch’ (see photos below). Don’t apply long excessive heat to the soldering points to avoid melting the switch
• fix the cable with straps
• profit from having the VR open for a clean job (blow off dust, clean traces of coffee, beer, sandwiches …
• close the VR: don’t forget to attach the battery cable and READ the warning on ‘remounting screws’ in Open VR09
• finished !

The foot switch (pedal):

The switch should be an unlatched (momentary) switch that closes the electrical contact when you push and opens when you lift the foot.
Switches that open on pressure and close on release also work but should be avoided for not permanently running current through the electronic board while the switch is in ‘rest’ position. Most after market switches have a little switch to invert the close/open behaviour (usually called ‘polarity switch’).
Basically any damper (sustain) switch or pedal works, even a ‘chrome piano damper pedal’ or those little boxshape ‘damper switches’ that are often come with stage pianos (and are useless as piano pedals).
A nice switch is the Boss FS-5U – it’s expensive – but you can watch out for clones (e.g. the ridiculously priced but quite reliable Lead LFD-1).

 

 

The TRS jack from rear side

 

The cable:

 

The soldering points to the ‘Rotary fast/slow button’: