canon ir5020..void areas

[Albonline]

voided areas on rear 1/2 of copies. repeats on the page diamiter of developer sleeve,have replaced laser, all coronas ,dev. unit HV pcb and transformer swapped main contr. PCB, replaced main drum motor and DV clutch, replaced registration assmy.

[etcopy1]

Have you tried developer drive clutch? How about turning off potential control?

[20YRSEXP]

Having a repeat problem that mimics the dev roller would seem to eliminate electrical components such as the coronas and HVT. That said... On that machine the laser writes and the Primary lays a clean or blanking charge so that would seem to also eliminate the Primary assembly. You have done the laser and Dev unit, those are the first two things that come to mind. With all you've done the problem seems to lean towards the drum, but I would also suspect the T/S assembly and I wouldn't rule out the fixing unit. Check the press roller and the HR bushings. Uneven pressure may cause uneven density. Thats a strange one considering all you've done. I hope some of this helps. Let me know how it's going.

[20YRSEXP]

If you haven't already, try to stop the paper before the fixing unit and see if the density is good. And if at all possible, (and I know this is really tough to do) try and see if the image on the drum is even. If it is the problem would be in the transfer or fixing. Stopping the page before the fixing unit would point to or rule out the fixing unit. Also if you haven't tried it already put some fresh paper in and see if it goes away.

[Albonline]

turned off pot. cont.. same problem...have tried to get dev. drive motor, unable to get so far...image on paper before fuser, unable to see void on drum surface...will try to catch it.

[20YRSEXP]

Before going crazy put some fresh paper in just to make sure that the problem isn't damp paper. Quick and easy is always the best way to go before getting to in depth.

[Albonline]

he, he, he did that first of all. if the primary is exchanged image is improved slightly, changeing developer bias and charge values has little or no effect.the image looks as if the developer sleeve stalls every reveloution, (or maybe slows down?) . has any body ever seen anything like this???

[20YRSEXP]

The problem with it being the speed is the copy is only effected on the rear half. Make sure we are both oriented the same. when you say the rear are you meaning the rear of the machine? The problem is lead to trail on the machine rear side? Because roller speed would effect the copy front to rear not just half. Do you have a transfer corona unit you can try?

[20YRSEXP]

Just thought of something. Its been a while so I don't remember, is there a glass between the laser and the drum? could it be dirty on one side?

[Albonline]

the image defect does go from edge to edge (front of mech. to rear) but is much more noticable on the back edge and tapers toward the front edge at about 17 degrees angle all but disapereing past 2/3 of the way to the front edge.

[20YRSEXP]

OK, That changes my thinking a little. I still would not rule out the drum. Do you have a used one? Even if it is not perfect it should show whether or not the drum is the issue. Check the drum edges for build up? The dev unit could be pushing away from the drum. Also, make sure the dev unit is pressing evenly. And if you haven't done it yet check your corona wire height.

[Albonline]

the drum has been changed twice. the ap kit is new the cros. are all new, just heard that 3 of theese units are being traded in, part, parts parts!!!

[mrfixit51]

Having a repeat problem that mimics the dev roller would seem to eliminate electrical components such as the coronas and HVT. That said... On that machine the laser writes and the Primary lays a clean or blanking charge so that would seem to also eliminate the Primary assembly. You have done the laser and Dev unit, those are the first two things that come to mind. With all you've done the problem seems to lean towards the drum, but I would also suspect the T/S assembly and I wouldn't rule out the fixing unit. Check the press roller and the HR bushings. Uneven pressure may cause uneven density. Thats a strange one considering all you've done. I hope some of this helps. Let me know how it's going.

Just a quick note to clear up some misinformation, the laser actually erases in this machine. It writes to white, not black. Here is a quote from the service manual:

The laser beam is then led through an imaging lens for removal of distortion, and is
directed to the positively charged photosensitive drum (areas representing white)
for the formation of a static image.
The laser beam is also used to blank out the non-image area.

I just did not want anyone chasing down the wrong alley based on a wrong assumption.

[20YRSEXP]

If you got that from the 5000 manual I stand corrected. Like I said it has been a while since I worked on a 5020. If I am wrong sorry for any confusion, maybe I have it backwards. I guess thats what happens when you start spending more time making sure others are doing their job rather then actually getting the hands on as often as I used to.
But Albon, What I thought about on the way home tonight was, did you run test prints from service mode to eliminate the reader as the issue?

[mrfixit51]

If you got that from the 5000 manual I stand corrected. Like I said it has been a while since I worked on a 5020. If I am wrong sorry for any confusion, maybe I have it backwards. I guess thats what happens when you start spending more time making sure others are doing their job rather then actually getting the hands on as often as I used to.
But Albon, What I thought about on the way home tonight was, did you run test prints from service mode to eliminate the reader as the issue?

No Harm, no foul,,, ;-) The 5000 family all uses that backward write to white mode. I believe they were going for darker blacks by going that way. I too thought of machine prints or network printing if it is online... I'm old enough to be vice president of service by now,, but still humpin' it in the field ;-)