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I need help identifying this 360 degree rotary encoder on my Roland SC-880 rack synthesizer. This one has become 'jumpy' and Roland claims the part is discontinued. So my only choice is to replace it. (or figure a way to open and clean it?)

This encoder has 20 detents and a push switch to select different modes. It's 17mm x 9mm at the base, and about 37mm tall. The synth came out in 1998 and I'm told Roland used Alps Encoders. What's the best way to go about replacing or fixing this?

SC880 ENCODER1

SC880 ENCODER2

SC880 ENCODER3

SC880 ENCODER4

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  • \$\begingroup\$ Have you tried filling it with contact cleaner already? \$\endgroup\$ – Ignacio Vazquez-Abrams Jul 1 '15 at 1:59
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    \$\begingroup\$ Do you have any idea how many ticks this encoder has per turn? That may be an important parameter to know for suggesting a replacement. \$\endgroup\$ – Michael Karas Jul 1 '15 at 6:57
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    \$\begingroup\$ Does this module mount via the threaded collar at the base of the shaft? \$\endgroup\$ – Michael Karas Jul 1 '15 at 7:07
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    \$\begingroup\$ This search at Digikey can get you started. All 20 pulse-per-turn encoders. I looked at 5 and they all had the same pinout as the ALPS. \$\endgroup\$ – Mr. Mascaro Jul 1 '15 at 14:26
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    \$\begingroup\$ @SynthGuy, ALPS doesn't make an encoder with that footprint anymore. The technology has evolved. You might have to panel mount, but the electrical pins should be in the same positions. You can cut off the clips and just be extra careful that the connection to the panel is good. \$\endgroup\$ – Mr. Mascaro Jul 1 '15 at 16:25
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The fact that Roland mounted this encoder on a small modular circuit board assembly does make it possible to think about finding an replacement encoder based mostly on the shaft mount, shaft size and knob attachment. The problem may be just a bit complicated if the existing unit also has a push switch action on the shaft.

You could make a new circuit board to accommodate the mountings of the replacement encoder. It is likely that you could even find some encoders that can direct mount via the panel collar and then you could direct wire to the encoder terminals without a circuit board.

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  • \$\begingroup\$ Yes, there is a push function on the encoder to access different menus on the synth. My skills are basically novice soldering so 'cleaning' this one, or finding a very close replacement are probably my only choices without paying a professional to do the job. \$\endgroup\$ – SynthGuy Jul 1 '15 at 3:32
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As a possible replacement encoder you may want to look at this part from ALPS.

enter image description here

If you can affix this with similar panel mounting you may be able to just wire to the leads of this device without even having to use that circuit board (just extend that existing harness as needed).

This particular encoder has 18 instead of 20 detents per turn.

Mouser carries this particular part (EC11E09244BS) in qty 1 for $3.21.

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  • \$\begingroup\$ Thanks for the suggestion. Are you sure this part is compatible? How do I know the shaft is the correct length and size for the knob? It mounts by the collar at the base of the shaft. \$\endgroup\$ – SynthGuy Jul 1 '15 at 12:16
  • \$\begingroup\$ Yes I see. The specs of collar 7mm and combine with shaft of 20mm are correct. Plus the knob spec looks correct. So now just need to be sure this will mount by collar? \$\endgroup\$ – SynthGuy Jul 1 '15 at 12:37
  • \$\begingroup\$ The wires would definitely reach the pins of the encoder without any problem. I wonder the purpose of the circuit board since it's only function seems to be routing the wires to the pins. \$\endgroup\$ – SynthGuy Jul 1 '15 at 15:39
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    \$\begingroup\$ The circuit board does several things. Eliminates hand soldered wires. And it provides a clean way to terminate the connection harness as 4-wires instead of 5 as may typically be soldered to this type of switch. (Clearly the switch and the encoder share a wire in the harness - probably a GND). \$\endgroup\$ – Michael Karas Jul 1 '15 at 17:13
  • \$\begingroup\$ My concern with your alps replacement was the 9PPR for 18 detents. I didn't know how that would affect the function. So, from digikey, I ordered ACZ11BR1E-20FD1-20C from CUI and EN11-HSM1BF20 from TT Electronics. These seem the closest fit, the TT even a bit more so (7mm brushing length) and less than half the cost. I think I should be able to solder one of these on the existing circuit board. I hope I'm on the right path, and value your help very much. Thank you! \$\endgroup\$ – SynthGuy Jul 1 '15 at 18:51

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