I am working on a T2300. The original problem was the mounting bracket on the bottom side of the carriage broke so the belt could not be attached.
I replaced the carriage (and belt while I had it apart). Now my bi-directional printing is off--it's "stair stepping" on each pass. The belt is tensioned properly. The encoder strip is clean. The rail is clean and lubed. The image quality diagnostic print shows everything is perfect except for the bi-directional--it's off approx. 1/8" in passes. I have run the printhead alignment multiple times, rechecked everything and I can't find anything out of place.
This wasn't there before replacing these parts. Maybe something with the third party belt?
Sometimes it can be caused by the encoder WHEEL located on the left side of the printer attached to the roller. I had one that was consistently skipping. When I checked the encoder wheel, it had some grease on it that was blocking it from being correctly read. I cleaned it off and reassembled, only to have it do it again after a few passes. Took it apart again and found the housing right above the encoder wheel has a glob of grease on it that was dripping down onto the encoder wheel. After cleaning it up, it worked fine.
Also check that you have the Carriage rear bushing in place on the back (top) of the carriage. It rides on the silver rail and will cause problems if not properly seated.
There should also be a calbration test you can do. Go to google and download the service manual and it will list the tests and how to perform them.
Turned out to be the new belt I had installed. It felt a little slicker than the original, and didn't tension as tightly as the original either. The new one I didn't have any difficulty attaching the tensioner. The old one I had to use a little extra pressure to get the screw started.
After triple checking everything I figured I'd go back to where I was before the problem started. I had to have the carriage as the mounting block snapped off my original carriage, so that left the belt. It's been printing perfectly since I put the old one back in.
BTW--if you put a refurb carriage in, you will need to swap out the line sensor from your original carriage or you will get a 59.3:00 error.
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