C550 Yellow Imaging unit going bad under 13K copies on DU

[PJFixIt]

I replaced this unit only 13000 color copies ago and it started printing striped image already. Swapped LED strips with magenta but no luck. Apparently it's 3rd unit last 8 months and not heavily used machine either. Please advice what I can look for to fix this problem. Sample yellow only is attached. All other color developers are fine. Thanks for your help. Machine errors out p-21 while adjusting gradation

[Mr Spock]

Re: C550 Yellow Imaging unit going bad under 13K copies on DU

Check the yellow developer bias and the yellow toner add system.

[WetPaper]

Re: C550 Yellow Imaging unit going bad under 13K copies on DU

This is an old problem that seems to crop up every once and a while...

Subject:
Poor copy quality. Void areas can be seen in the lead-to-trail (sub-scan) direction.

Description:
Poor copy quality. Void areas can be seen in the lead-to-trail (sub-scan) direction.
Solution:
CAUSE: Image Unit failure (the Image Unit is losing developer). See the attached file for a print quality example.

SOLUTION: The IUs have been modified. Replace the IU with one manufactured after 2/16/2011. The lot number on the IU box is the manufacturing date.
Example: Lot number: xxxxx1216x (2011/February/16)

[MAD0RAM]

Re: C550 Yellow Imaging unit going bad under 13K copies on DU

All units should be manufactured after that date by now.

[PJFixIt]

Re: C550 Yellow Imaging unit going bad under 13K copies on DU

Thank you all (esp. Wetpaper). I will check the manufature date (if they still have the box) and get a newer unit.

[dallas]

Re: C550 Yellow Imaging unit going bad under 13K copies on DU

Open the Yellow IU and check the grid for waste toner contamination.
In this case, change the Transfer Belt Unit.

[PJFixIt]

Re: C550 Yellow Imaging unit going bad under 13K copies on DU

Opened the IU and the grid is clean. Noticed a similar pattern on the developing roller - instead if developer there were bands of yellow toner while turning the roller, due to reduced amount of developer, I guess. This and the previous 2 prematurely failed yellow IUs seem to have 2012 manufacture date. The current IU lot# is XXXXF2711A, meaning July 2012? Could there be some thing else wrong with this C550?. Thanks in advance.

[EarthKmTech]

Re: C550 Yellow Imaging unit going bad under 13K copies on DU

you dont need to open the imaging unit to see charge section contamination.

shine a light in and look through the ozone duct gap at the base of the yellow iu after pulling out the charge cleaner all the way. If you see brown stains on the sides of the the charge unit you have a failing transfer belt - these have been modified for this very reason and seal better now. If you see black on the walls you have a failing black imaging unit and this is killing the yellow - this usually also includes black toner deposits at the edges of the transfer roller.

had this problem many times now and its almost always either the transfer belt leaking or the black imaging unit spoiling it, there is also a possibility of the waste toner collection unit that sends the waste toner from the belt to the box leaking at its seal where it mates with the belt.

Also note, that once the charge unit is contaminated the machine will destroy the imaging unit all by it self. There does not need to be any actual fault with the developing side of the IU - lost developer as per your print sample becomes a symptom and is not the cause.

In addition i will also say that, if the toner supply shutter leaks at the bottom of the toner hopper and you have toner puffing at time of adding, this will destroy imaging units too. this will be evident by piles of new, clean toner on top of the imaging unit.