Hi all,
I know this machine is ancient, but it just keeps going, except for this one issue that has me stumped.
For yellow screens, about 50% or less, I'm getting uneven density in the feed direction, specifically a thin band of extremely low density (about 15-20mm) wide, repeating at about the same interval as the drum circumference (188mm).
See attached for scan of a test pattern. It's #53, Dot 1 screen, with value 32 for Y only. Arrow is feed direction. I also did a levels adjustment on the scanned page, to make the difference easier to see. It's VERY visible when yellow is mixed with any other color in a print. It becomes worse at higher values, but then solid yellow (255 / 100%) is completely fine.
My first thought was, given the repeat distance, to swap the drums. That didn't help. Drums from the other colors, which don't have this problem would show it immediately when swapped to the yellow position, then back to normal when returned to their original color. I also swapped the following with new parts:
- yellow charge unit
- transfer belt assembly
- lower 2nd transfer roller
- brand new drum in yellow position for good measure (effect appeared immediately)
Additionally:
- cleaned the 1st and 2nd transfer contacts at the back of both belt units, and inside the printer
- cleaned the laser window
- cleaned the PGC and registration sensors
- gamma offset adjustment
- gamma sensor adjustment
I ignored the developer, since it's only about 50% life, and solid yellow prints OK, but I could try changing that too.
I'm thinking it's either a 1st transfer or laser issue, especially since the machine is so old, and has 5 million clicks. Will try the following next:
- yellow laser
- High volage unit /2
Any thoughts or suggestions? Maybe I'm missing something obvious? Thanks in advance.
I know this machine is ancient, but it just keeps going, except for this one issue that has me stumped.
For yellow screens, about 50% or less, I'm getting uneven density in the feed direction, specifically a thin band of extremely low density (about 15-20mm) wide, repeating at about the same interval as the drum circumference (188mm).
See attached for scan of a test pattern. It's #53, Dot 1 screen, with value 32 for Y only. Arrow is feed direction. I also did a levels adjustment on the scanned page, to make the difference easier to see. It's VERY visible when yellow is mixed with any other color in a print. It becomes worse at higher values, but then solid yellow (255 / 100%) is completely fine.
My first thought was, given the repeat distance, to swap the drums. That didn't help. Drums from the other colors, which don't have this problem would show it immediately when swapped to the yellow position, then back to normal when returned to their original color. I also swapped the following with new parts:
- yellow charge unit
- transfer belt assembly
- lower 2nd transfer roller
- brand new drum in yellow position for good measure (effect appeared immediately)
Additionally:
- cleaned the 1st and 2nd transfer contacts at the back of both belt units, and inside the printer
- cleaned the laser window
- cleaned the PGC and registration sensors
- gamma offset adjustment
- gamma sensor adjustment
I ignored the developer, since it's only about 50% life, and solid yellow prints OK, but I could try changing that too.
I'm thinking it's either a 1st transfer or laser issue, especially since the machine is so old, and has 5 million clicks. Will try the following next:
- yellow laser
- High volage unit /2
Any thoughts or suggestions? Maybe I'm missing something obvious? Thanks in advance.