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  1. #1
    Senior Tech 250+ Posts Jake2o's Avatar
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    C6500 printing black

    So I have this 6500 that is printing black sheets indicative some sort of failure of the charge corona being able to charge the drum; simple enough under normal circumstances, but this is the strangest fault I have ever come across. After more days than I care to mention of messing with it I put a process unit in out of another machine (just the frame) and it worked perfectly. Put the original frame back in and it is back to printing black. I have swapped the drum guides with those of another colour and that hasn't made any difference, neither has swapping the static sensor and even the erase lamp just for the hell of it. I have taken out the ADU and observed the PU going in and out and it glides and locates as it should.

    If I print a black test pattern 11, while the sheet is black it is still possible to see the print (just about) which suggests that the drum is getting a bit of a charge, but not enough.

    It is not the following: Dev housing, Drum, drum guides, corona, write unit, erase lamp, drum drive shaft, transfer belt assembly, or static sensor.

    It is something else in the process unit frame because the fault goes away when I change the frame, but for the life of me I cannot see what. Are these known to arc out somewhere?

    Any ideas would be extremely welcome.

  2. #2
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    Re: C6500 printing black

    think you will find the cel circuit on the bad carriage is grounded. turning on the lamp. could possibly be the grid grounding, but assume you eliminated the obvious stuff already.

  3. #3
    Service Manager 5,000+ Posts
    C6500 printing black

    Phil B.'s Avatar
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    Re: C6500 printing black

    Quote Originally Posted by Jake2o View Post
    So I have this 6500 that is printing black sheets indicative some sort of failure of the charge corona being able to charge the drum; simple enough under normal circumstances, but this is the strangest fault I have ever come across. After more days than I care to mention of messing with it I put a process unit in out of another machine (just the frame) and it worked perfectly. Put the original frame back in and it is back to printing black. I have swapped the drum guides with those of another colour and that hasn't made any difference, neither has swapping the static sensor and even the erase lamp just for the hell of it. I have taken out the ADU and observed the PU going in and out and it glides and locates as it should.

    If I print a black test pattern 11, while the sheet is black it is still possible to see the print (just about) which suggests that the drum is getting a bit of a charge, but not enough.

    It is not the following: Dev housing, Drum, drum guides, corona, write unit, erase lamp, drum drive shaft, transfer belt assembly, or static sensor.

    It is something else in the process unit frame because the fault goes away when I change the frame, but for the life of me I cannot see what. Are these known to arc out somewhere?

    Any ideas would be extremely welcome.

    could the contacts be dirty or damaged/bent?

    typically all black pages are do to contact failure ....

    how many pages on supplies/machine?

    are any drums/belt/transfer units EOL or near?

    was the unit working properly before?

    did you clean the machine?

    if you send a print job can you see the text under the all black?

  4. #4
    Senior Tech 250+ Posts Jake2o's Avatar
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    Re: C6500 printing black

    It is probably the grid grounding, but I just do not know what on.

    If I send test pattern 11(beam check) then I can definitely see the pattern under the black is as it should be. I can't do a copy or print outside of test mode because it is locked in adjustment mode, and because the toner is painted on the drum it just errors out.

    It can't be the drums or the coronas themselves because the all work perfectly if I put them in another process unit frame.

    It is a customers machine that typically they bought of fleabay and so I have no idea of it's history. When I went to it, it had the bottom right locking shaft and locking roller missing so I have fit new ones. I think it is a bit of a pup to be honest, but it is a good customer with another machine that I look after so I don't mind going the extra mile to try and revive it. It also had the infamous 3102, but that is easily remedied. It has had issues in the past and whoever worked on it previously probably wasn't entirely sure what they were doing because every plug and every socket is marked up.

  5. #5
    Senior Tech 250+ Posts Jake2o's Avatar
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    Re: C6500 printing black

    Quote Originally Posted by Albonline View Post
    think you will find the cel circuit on the bad carriage is grounded. turning on the lamp. could possibly be the grid grounding, but assume you eliminated the obvious stuff already.

    Ahhhh! you might have hit on it there, I just never thought of that for some reason. The lamp is wiping it as fast as the grid is charging it, that would make perfect sense; will give it a go tomorrow and post how I get on.

    Thanks.

  6. #6
    Senior Tech 250+ Posts Jake2o's Avatar
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    Question Re: C6500 printing black

    So I tested the Erase lamp circuit and checked it in state confirmation and it operates exactly as it should which leaves me absolutely clueless as to what is wrong with this carrier. I have now taken it out and put a carrier in from another machine while I discover what is wrong with it, but there is nothing left to check (certainly nothing obvious). It has to be the drum earthing out somewhere, but where is anyone's guess.

  7. #7
    Senior Tech 250+ Posts
    C6500 printing black

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    Re: C6500 printing black

    Quote Originally Posted by Jake2o View Post
    So I tested the Erase lamp circuit and checked it in state confirmation and it operates exactly as it should which leaves me absolutely clueless as to what is wrong with this carrier. I have now taken it out and put a carrier in from another machine while I discover what is wrong with it, but there is nothing left to check (certainly nothing obvious). It has to be the drum earthing out somewhere, but where is anyone's guess.
    I suggest measuring ground conductivity on the black drum shaft while printing.
    Nothing like day after day

  8. #8
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    Re: C6500 printing black

    Quote Originally Posted by tulintron View Post
    I suggest measuring ground conductivity on the black drum shaft while printing.


    also check the developer bias system shorted to gnd?

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