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M100 foldback instructions

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  • M100 foldback instructions

    So I’ve been toying with the idea of adding the full manual fold back to my M111 . I was curious if anyone could lend a hand and give me detailed instructions . I understand where the key contacts go and how to find the corresponding notes . But don’t quite grasp what you connect the new key contacts to and what kind of conductor you use . Any help would be appreciated ..

  • #2
    You connect to the terminal strip on the manual chassis in question, using the resistance wire that's welded onto the key contact.
    Current organs: AV, BC, A-100
    Current Leslies: 22H, 142, 147, 760
    Organs in the past: L-100 (several), M-100 (x2), T-100, E-100, CV
    Other keyboards: Roland FP-4, Yamaha DX7, Yamaha TX81Z, Yamaha Motif ES Rack, Korg Krome, Novation Mininova

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    • #3
      So where does this resistance wire come from though is my question I guess ? As the new contacts have none ... do I take the old wire from the donor organ aswell ?

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      • enor
        enor commented
        Editing a comment
        Yes. De-solder at the terminal strip, untangle and remove.

    • #4
      If you want to add full foldback to a spinet, the first thing you do is go get at least one more spinet.
      Then you go look up HammondWiki where there are charts and pics and all kinds of info.
      You can go to YouTube and see a few offerings.

      I'm not giving you the shove-off. I'm really not. There's a lot of steps; a lot of components; and a lot of moving parts to this operation. I've done two.
      You need wired contacts and full length bus bars. It's not for the timid or the busy because there's lots of fiddly bits to dive into.

      When you're done, it will sound different and, in most peoples' opinions, better. You'll want a Leslie or something like a Leslie, even if home-brewed. But that's for another post.

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      • enor
        enor commented
        Editing a comment
        Just to pick nits: The M-100 already has full length busbars in all positions, so at least it's a little bit easier to do this procedure on than the M-3 in that respect.

      • tiredoldgeezer
        tiredoldgeezer commented
        Editing a comment
        Good catch!
        I've only done M-2/3 spinets. Was unaware of the difference in that respect.
        To my knowledge, the only source for full length busbars is another spinet. If it already has that, much of the trouble is over.

    • #5
      Thanks for the feed back . I have an l100 (non functional) where I’ve been getting my parts from . And a Leslie 142 (which I love )! I’m fully invested into the project . To be clear this is an m100, so it has full length bus bars . I’m understanding everything .. almost .. just looking for a definite answer on weather or not to re-use the resistance wire from my l100 . As I’ve found no clear info anywhere online ..... I’ve combed the internet ..

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      • enor
        enor commented
        Editing a comment
        If you have a donor L-100, just take the contacts from that one, including the piece of resistance wire welded onto it. De-solder at the terminal strip, remove, re-use in new organ.

    • #6

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      • #7
        Alan Dubois offers the correct contacts and resistance wires on eBay:

        https://www.ebay.com/itm/Upper-Lower...4AAMXQDjhQ55Fs

        More importantly, he offers very detailed and exact instructions with photos. I just completed full foldback on a 1965 M103 with his kit and also added tapering to the upper octave at the same time. Makes a huge difference in sound.

        If you root around on the internet and also here in old posts, you can find enough info to get it figured out, more or less. But Alan's instructions that come with the kit are well worth the money. It includes full disassembly of the organ to get down to the parts. I can't give you Alan's proprietary instructions, but I did do a post not too long ago on here where I included some uploads of some printable guides for assisting with the foldback and tapering. The key is to do all contacts for one frequency at a time, go slow and double check that every contact you add gets seated all the way into the correct slot. Getting the contacts all the way through all the slots can be a bit fiddly and requires patience and never force them as they will bend easily. You will know when they seat properly after you have done a few. Also, if your organ has the thin green resistance wires instead of the cloth covered wires, be very careful when you are inserting the contacts that you don't snag one of the other wires in the new contact. The edges are sharp and they will cut through the thin insulation and you will get two tones on both contacts when either is played. I put up a post earlier about that with a picture of the snag.

        Alan's instructions also recommend to test every single contact and bus bar combination. It's time consuming but you will know for sure that all is well before you put the whole thing back together.

        One other note is there is a lot of stuff on here and elsewhere about the "gooey foam" problem inside the manuals. Sometime in 1960's they switched from felt to foam, and the foam deteriorates into goo that can eat through the wires. Mine had the foam, but it was disintegrated and dry, not gooey. I removed all traces of it carefully and replaced it with 1/8" thick felt by 1/2" wide that had sticky tape on the back.

        Good luck!

        Last edited by tmccann; 06-18-2020, 12:37 AM.

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        • enor
          enor commented
          Editing a comment
          Gooey foam isn't really an issue on spinet models. Yes, there's a foam strip present in the manuals and yes it does deteriorate just like in the bigger instruments; but the strip in the spinet isn't as wide and it's placed differently. This different placement means that even if the foam strip does deteriorate and turn into a gooey mush, it's not going to reach the resistance wires and therefore not going to cause problems.

        • tmccann
          tmccann commented
          Editing a comment
          I never thought about it that way. It sits close to the wires but underneath them. So unless you are doing a lot of Keith Emerson moves with the organ, it really can't get to the wires. Something for spinet owners to cheer!

      • #8
        Thanks everyone for the feedback . I got all my contacts, with resistance wire ready ... my final question .. how important is the length of the resistance wire ... will it make a difference if I don’t pay much attention to it ..?

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        • tmccann
          tmccann commented
          Editing a comment
          The resistance wires in spinets are either 16 (most) or 18 (some) Ohms at the length from the factory. If you shorten them the resistance will change. If you are harvesting them from a spinet, measure them and make sure they are ~16 Ohms. They are much easier to install if you have the factory loop on the end vs. trying to wrap them around the lugs. I left all mine the factory length. I installed all contacts for a particular tone, then routed the wires in the loom under the strings (with a wire pick tool) just like the contacts that are already in place, and then carefully placed the loop over the lug for that frequency. Once I ran all the wires for a particular frequency I then soldered them to the lug all at once. Then move on to the next frequency. I tried to upload some pics but it is failing for some reason. I'll try again later.

          Be extremely careful in unsoldering and soldering to the lugs if they are held by black plastic instead of bakelite. The black plastic will melt and the lug will fall away. Repair is not easy. Solder quickly and if you have problems let it cool down and start over.

          There are grounded contacts for tones 49-61 in the last row of contacts that are connected to the ground lug to the left of the last tone 91. These contacts are there for percussion and need to be removed before doing the foldback. To remove existing contacts, grab one side of the contact with needle nose pliers and tweak it to the left or right (as appropriate) and you can pull it straight out. Practicing this on the grounded contacts is a good way to get the feel of removing and inserting contacts without damaging anything important. Be careful not to snag any of the other resistance wires when pulling out or inserting contacts. Also, avoid touching the end of the contact where it touches the bus bar with a short palladium wire. I cleaned all mine with alcohol before inserting.

          As mentioned below, cleaning the bus bars is critical. I used NEVR DULL wadding polish and they shined up nicely. Be careful not to bend the bus bars. But the good news is on the M100 models they are super easy to re-insert vs. the flat bars on the consoles and older spinets. If you run into any resistance inserting one, just rotate them and they will pass through the next gate. It is way easier to insert the contacts and see they are in the right place with the bus bars out. There is a huge debate about whether to lube the bus bars or not. I used a thin coating of DeOxit 5 on mine.

          As I mentioned earlier, strongly consider adding tapering at the same time. You can add 27 Ohm resistors to a new wire and add it on top of the 16 Ohm resistance wire. You end up with 10 Ohms (parallel) which will fatten up the upper octave. You can google tapering and see the details.

      • #9
        Just another advice. From my experience with adding foldback I'd say that it is very important to clean the busbars if new ones are installed. I did foldback once on an m2 and did not pay much attention to the busbars. I had to do the whole thing again because the tones were clicking way too loud. And even if the m100 already has full length busbars, you might want to clean the busbars as well. At least if you think some of your tones are scratchy or have too much keyclick and using the busbar shifter does not help. You'll have the manual(s) open, so you won't get a better chance of doing that job. Others disassemble the manuals only for cleaning the busbars.

        greetings Christian
        1960 M3, 1953 M2 converted into M3, Leslie 122, Ventilator II, Viscount Legend Solo

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        • #10
          Two things are extra problematic when doing this procedure on an M-100:

          1. The terminal strip is made from a very heat sensitive plastic. It easily melts and the lugs come loose

          2. The metal in the resistance wire is of a type that's hard to solder - the solder doesn't "stick" easily. This means that you often have to try several times, and problem #1 comes into play.

          To get around this problem, I don't solder the "new" resistance wires directly to the terminal strip. Instead i use a short piece of normal, insulated wire... just an inch or so. I splice the new resistance wires to this piece and insulate the splice with heat shrink tubing; then I solder the other end of the short wire to the terminal strip (which of course is quick and simple because it's made of solder friendly metal). Yes, the terminal strip gets a bit more crowded in this way, but it's still worth it because of the eliminated risk of messing things up badly.
          Current organs: AV, BC, A-100
          Current Leslies: 22H, 142, 147, 760
          Organs in the past: L-100 (several), M-100 (x2), T-100, E-100, CV
          Other keyboards: Roland FP-4, Yamaha DX7, Yamaha TX81Z, Yamaha Motif ES Rack, Korg Krome, Novation Mininova

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