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Choptigan

by Zac Rae

After I came across my third optigan, and my second in one week, I decided that my extreme lack of space was going to finally motivate me to attempt a “cut-down” on an optigan, much like the kind popularly attempted on Hammonds to make them more portable for road use. The idea had been milling in my head for a couple years but I was awaiting a second one so I could leave one in “mint” condition. If anyone seriously intended to tour with an optigan, this might be the way to go, but you would have to be psychotic anyway. Not like the sort of person who would bother to do something like this to an optigan is in sound mental condition so we should probably just drop the subject.

Choptigan Image
Choptigan Image
Choptigan Image
Choptigan Image

The optigan I chopped was a 35011 ; the cabinet design is really the only one of the various optigan designs that I’ve seen that will easily facilitate a chop, as the top is in one piece and it is basically separate structurally from the rest of the cabinet. The standard 35001 cabinet will not work easily and you would have to redesign or construct a new top piece – the electronics would be the same though. Its basically a wooden box so anyone with woodshop from high school can probably do it. Its just extra work It would also be feasible to integrate it into a road case ala the orcheston D style case. That is for someone else to do. What follows are basic instructions for a 35011 chop.

Unscrew the back panel. Keep the screws and the panel – clean off the gunk if you haven’t done so.

Remove the top piece. There are four screws at the base of the top section that unscrew it, located at the four corners of the machine pointed up. They are the outermost screws. The inner screws remove the entire keyboard mechanism from the base – don’t do this yet!

Next follows a lot of disconnecting wires. Remove the plugs from the reverb tank and un-screw that from the base. Set it aside. Remove the wires that lead to the volume pedal LDR from both voice amp boards. These are marked D and E. Finally remove the wires going to the speakers and the headphone jack, which can also be totally removed. Keep all the wires for use later. Depending on your concentration level with tons of wires floating around, you can leave the rest in place, or take out what is necessary for enabling you to work inside it.

The vertical mounting board that holds the two amps, the transformer and the LDR can now be discarded. I would unscrew the mounting board first and then remove the components, but you can do it the other way around. The two amps and the transformer can all be mounted in the section directly behind where the spare discs go. There’s normally a piece of black card in there which has to be removed to clear the area. You can see vaguely (behind the mess of wires) on my picture how that works. The components all fit in their quite nicely, and you shouldn’t even have to change any of the wires to longer connections. Drill holes and mount them there with the original screws. I also drilled a few holes to screw it some clasps to organize the wires. Now all the main optigan components are mounted in the top section of the machine.

At this point in time, if you haven’t done it yet, clean out the foul black goop from the button contact section. I use a mouse pad to replace it and it works fine, adding a bit of spring and cushioning. I would also remove the latex contact strip from beneath the keys, and give those contacts a thorough clean. Its actually worthwhile doing this beforeyou take it apart so you can hear to make sure youíve got it all taken care of.

The reverb tank fits best in the front section where the spare discs normally go. Couldn’t find a nice way to screw it in to I used velcro which works perfectly. You can reconnect the original wires that went to it.

Next is to attach two ºî jacks for the outputs. I thought it best to use two mono ones, but you could go for a stereo jack, or use RCA connectors, depending on your preference. To bypass the LDR circuit, solder wires from both D and E (use the original wires) to the tip. Attach a 470 Ohm Resistor between the ring and the tip on the jack. Repeat this for both keyboard and chord side. On the keyboard side, connect the ring on the jack to F on the board. Remember the keyboard amp has the extra jumper on in. This connects F to the ground loop. It is not present on the chord half, so instead run the ring end of the jack into the main ground connector which is on a multi way connector just to the left of the lamp assembly (looking at it from the back) The schematic provided for a line level out from the service manual does not work for the chord side and this is why. An alternative would be to add the jumper wire in, but I suspect that would add a ground loop problem – similar to the problem encountered using a stereo jack in the headphone output, rather than a mono one.

That does it – you can remove the whole top assembly from the base and it is now a self contained unit. I just sawed the back piece to an appropriate size and used that for the back. The base is another matter, and will present a problem if you do not use an X brace stand as in the picture. The base of that section of the optigan is not even, there are bits and bobs sticking out. Sooner or later, I will make a real bottom piece for the thing. Feet would be good too, but this works fine for now. The volume is permanently up and you’ll have to use an external volume pedal now, which I personally find useful for recording purposes. The only final touch is to add your own choice of snazzy paintjob – this one was actually painted white like this when I bought it (!), but I probably would have done something silly with it anyway so its just as well.

Good luck if you attempt this operation.

I’d like to hear from anyone else who is attempting it or has done something similar. Next up is a 6U, 19″ rack-mounted and MIDI-ed optigan module… Look for it in coming months.

 
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