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Generally, adding full foldback to a spinet requires the addition of some missing key contacts. M2 and M3 spinets also require the replacement of (at least) three non-full-length busbars for each manual. Thus a donor organ, or some other supply of parts is required. M100 and L100 series usually have full-length busbars and need only the "missing" contacts to add foldback.


GeoffWilliamson wrote a great page about this modification. Unfortunately, his page seems to be off-line now, but itís still available from the wayback-machine here.

?KarlFrick has added foldback to his ?PortaB, and he took a nice set of pictures while he was doing so.


If you don't have the nichrome resistance wires, MikeFulk suggests using 16 ohm, 1/8 watt resistors (which fit on the end of the key contacts) instead.

Parts Sources

AlanDuBois has Foldback Kits available on eBay for M2, M3, M100, L100 and PortaB which includes detailed documentation (with lots of photos) on how to perform the foldback modification for these models. Search eBay for "Hammond Foldback" or

Also see CategoryPartsSources.


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