Lexicon JamMan Encoder Repair
Lexicon JamMan Encoder Repair

Other than the encoders, this group of Lexicon products are remarkably reliable and are still in use all over the world to this day (2007). Since I had a hand in their development, I try to do what I can to keep the devices working so I came up with a mod to replace defective encoders. I wasn't able to locate exact replacements for the encoders but I did find a replacement that I was able to retrofit:

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=CT3003-ND

The parts I got have the number: 288T232R31 on them and, though I was able to get them to work, they have 5 problems:

  • The shaft is too long - I had to cut it.
  • The pins are wire hole type not pc mount - I cut them off and just tack soldered the part to the board.
  • The mounting hole is too big - I had to drill out the hole to make it fit.
  • The shaft is round - I had to find a replacement knob (Radio Shack)
  • The detents are not as distinct. It's not as easy to tell the position of the encoder. -Nothing could be done about that. No biggie.
  • NOTE - This is an inverted graycode encoder. Circuit can be modded to accept the Standard Graycode though otherwise position and value do not correspond. - Tito

Despite all of these problems, the part does work and even with all of these extra steps, only took about an hour to complete.

I video taped myself performing the mod which I've posted here:

Bob Performing The Encoder Mod.wmv - Video (133MB) 11-17-2007

This is still a rough cut of the video but does go over all the various steps involved in performing the mod along with other helpful hints about maintaining these devices. We'll be updating the video over the coming weeks so, if you are interested in this sort of thing, check back for the updates.

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