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Hammond T- Series Resistance Wire

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  • Hammond T- Series Resistance Wire

    Hi I can't find this information anywhere; on the internet or in the manual.

    What type of resistance wires are used in the T - Series organs? I know that the M series use 16 ohm resistance wire, is it the same for the T - Series?

    Some of them have disconnected from the key contacts, and some have broken. If i theoretically knew which resistance wire to replace it with, does the length and the gauge of the wire matter at all?

    Thanks, I can't find any sources online to help with this sort of repair.

  • #2
    "Resistance wire" can be made from various metal alloys that have different "resistivity". These metals can be drawn into various gauge wires which depending on the gauge and alloy, can have different "ohms per foot" specifications. Basically what you would want is an alloy that is "solderable" with ordinary solder and has sufficient ohms per foot to reach from point A to point B in the manual. A simpler solution might be to either create some slack in the existing wires and solder them back, or perhaps splice in short pieces of copper wire to bridge a gap.
    Tom in Tulsa

    Fooling with: 1969 E100, 1955 M3, 1963 M100, Leslie 720

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    • #3
      I am unsure about T series resistance wires, but they might be 16 Ohms. You should be able to tell quickly with a multi-meter, but make sure one end of the wire is disconnected so you are getting a true reading.

      If they are 16 Ohms, you can get donor resistance wires from Alan Dubois. Go to eBay search for Hammond foldback kits. You can then contact the seller (Alan) and ask if you can buy a few individual contact and wires vs. the whole kit. Replacing the contacts and the wire at the same time makes it a lot easier. You can read about how to do foldback on here and elsewhere to get a sense for how to replace wires and contacts.

      If you want to make your own wires, read on...

      What I did for new tapering wires in my M100 was to use 32-gauge prototyping wire (also known as "blue" wire - Mouser and Digikey sell it) and soldered resistors to the end at the contacts to get to the desired resistance in Ohms. There is negligible resistance in prototyping wire, so the correct resistor is all that is needed.

      I made all the wires to replace at once, like a little assembly line. Resistors were 1/4 Watt metal film type. I cut one end of each resistor lead ~5/16 inch long (leaving one end long to handle it easier), stripped the same amount of the wire, tinned both ends, and soldered the new wire to it in parallel so there is a good amount of connection. Tug on in hard to make sure it is solid. Then I put on a short piece of heat shrink tube to insulate that. DO NOT get a heat gun anywhere near the contacts in the manual. It will easily melt the plastic contact holders and then you are in big trouble. For the other end of the wire, the part that attaches to the lug, I stripped about 1 inch and twisted it back on itself to make the loop. I think all the blue wires I made were ~18 inch in total length, but I can't remember for sure. I just made the new wires the same length as the original resistance wires so I could weave them into the looms the same way as all the other wires.

      Once you have all the wires made, cut the remaining end of resistor to about 5/16" in length (any longer and it makes it harder to fit). That end gets soldered right to the contact. To install the new wire, you should pull out the contact with the bad wire some from the holders so you can solder it more easily. No more than 1/2 inch so it goes back easily. If you pull the contact all the way out it can be fiddly to get it all the way back in. You can do this by grabbing one side of the contact with needle nose pliers, bending the contact a little to one side to free if from the plastic holder, and pull it up slightly. It's easy to do it once you get the hang of it.

      Once the contact is pulled back, I cut the existing wire to be replaced flush with end of the contact, put on a very small dab of solder flux, and soldered the end of the resistor so the resistor body would sit vertically just above the end of the contact. Then push the contact back in so it seats and check nothing is binding. There should be a little play side to side and up and down, but it should be secure. If there is no play, then it's possible it is not seated properly. Look at the opposite end of the contact from wire end near the bus bars and make sure you see the end of the contact poking out in the right slot and on top of the bus bar, not underneath. There should be nine contacts poking out and all should look the same.

      Once the contact is inserted, then I carefully routed the wire in the loom in the slots and under the strings like all the other wires. The last step is to solder it to the correct frequency lug. If there is more than one wire to solder to a frequency lug, I would run all the wires to that at the same time before soldering. If the lugs are mounted in black plastic instead of bakelite or phenolic, be really careful with soldering iron and work quickly. If the lug falls out of the plastic holder it is a whole other nightmare to fix.

      Keep in mind that each of the 9 contacts for individual keys go to different frequencies. You will need to number the frequency lugs for each tone, and map each contact for each bus bar to the correct frequency.

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      • #4
        Kon Zissis recommends repairing the wire up to a point, but if there are too many breaks he says just to put in a 16 ohm resistor and run a fine, enamelled wire straight to the terminal strip. I've done it on my T and it can look pretty tidy. I can't remember if this pic was from the repair or the tapering mod...
        ‚Äč
        -1958 Hofner 550 archtop guitar -1959 C3 and PR40- -1964 Busillachio Harmonium- -1964 M101-
        -1967ish Leslie 122- -1975 T500 (modded..chopped, and reassembled!)-
        -DIY 760 FrankenLeslie/rat hideout-
        -1980 Electrokey Electric Piano- -Yamaha electric Harmonium (early 80's?)-
        -1990 Jansen GMF150 amp- -1992 Korg 01W/fd- -1992 G&L S-500 geetar.

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