Yeah, yeah, ... primary charge shorting for cyan. It's a Saturn KM-250ci. Sorry I didn't save any of the samples.
But here's the thing: It's had three cyan drum units, and it goes away for a while each time. Then I noticed that most of the screws were stripped out on the toner hopper assy. It's no wonder since it's been off/on about a zillion times in the last 9 years. So I re-tapped the holes 10-32 (about 4.5mm if there was such a thing) and installed 5 new 10-32 screws. The theory is that I would get better drum ground contact with the hopper pulled snug up to the frame (not just one screw at the left). I also used some conductive grease at the drum grounds.
Two weeks later and I'm back. Same blue bubbles. Cyan gradations of 15% or less are blank on my test pattern. So just for kicks I swapped cyan and magenta drum units. Cyan instantly filled in to 40% fill on my 15% pattern (very heavy fill). The first calibration made it worse, almost 60% fill for my 15% pattern. The second calibration brought it around to what I'd like to see: 15% fill. I expected image anomalies to move to magenta, but that didn't happen.
Self-calibration is clearly compensating for something with the cyan drum/primary charge ... but what exactly? I left with mostly perfect images for a Saturn, but I don't expect it to hold.
I think both the customer and me want this machine to retire. =^..^=
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