My press has it out for me lately. I’ve been hearing this clicking associated with the ink drum. It started a couple days ago, just a couple clicks here and there, but has sounded more and more frequently the more I print. I took a short video and you can hear some of the clicking. It sort of looks like the chain might be bouncing off something, but it’s getting worse and I don’t need the chain snapping.
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Your chain is contacting the guard. The holes for the chain’s pins elongate over time, and the cumulative effect makes it longer. I quick fix is to remove the guard or cut away enough so the chain clears. There id probably not enough slack in the chain to remove a link.
On some models the motor can be moved to take up the slack, but access is very difficult on an SP20. When tome allows you can replace the chain.