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raplma
07-12-2021, 06:52 PM
Hello
This is one of those "has anyone come across this before"... so any pointers and any suggestons most welcome.
C7000, 11M+ clicks (yes high I know), only OEM consumables...

The image below shows a repeating ghostly black mark that appears on anything printed irrespective of image/colour, including no image jobs/blank sheets, test patterns etc.
In the pic, you'll see the top edge of an SRA3 sheet where the direction of print is from left to right and the mark is on the side of the paper towards the rear of the machine
The mark although from a distence looks the same, actually varies in the style of the 'peaks' or ripple effect.

FYI - Black dev and black dev unit replaced back in March and dev is at 66%.
Upon the appearing of the mark I have replaced the black drum unit with new oem drum likewise corona.
The pattern repeats roughly every 186-196mm which is why I replaced the drum unit, but there was no change.
The TB is 145% of life, but visually in good condition.
Relative humidity was higher than usual for us at 45% usually 35% (as measured on the machine), there is basic air conditioning in the room where the machine is housed too which includes humidity control.
Note: there are no codes being thrown by the machine, it will hapily run any job in this condition, indeed I ran the job I needed to 1up SRA4 instead of 2up SRA3....

I have run the tonor desity restore as it had run a long B/W job at the end of last week, only 10% coverage though, as well as the tonor refresh for black.

The one thing I am yet to try is the panic stop and look through the process unit to see where the image is residing, although I am expecting it to appear on the drum. In my mind I am unable to work out how - if it is the write unit - how is it possible to excite the drum in such a way.

Anyway... yes I am an end user, but endevour not to take your expertise for granted and am most grateful for any suggestions, and contribte to this forum when appropriate. We've had KM MFP's and presses for 13 years and all bar the first one have been maintained by ourselves, so not a complete numpty, but happy for someone to prove me wrong there :)

Mark

49671

tsbservice
07-12-2021, 08:04 PM
Hi Mark glad you're hanging around mate.
Unfortunately I have no production machines in the field but if you need any guide for this model just PM me. You have interesting problem here and I would love to fight it in person. This is looking like something is causing a small bump on mag roller and it touches drum surface.
I'm sure other guys here will have more insights. Good luck.

Synthohol
07-12-2021, 08:17 PM
first glance id check the fuser belt.
if you roll one mark on top of the next you get the diameter of the offending roller/belt/drum.

blackcat4866
07-13-2021, 12:23 AM
Did you remove the red painted shipping screws on the drum blade mount? If not the drum blade will not touch or clean the new drum. I think everybody has done it at least once. 188mm is the right interval for drum cleaning. =^..^=

raplma
07-13-2021, 09:22 AM
Morning all
It's a great feeling to arrive at the factory in the morning fire up the PC and see you guys many thanks for your replies.

tsbservice: So, if they ever get teleportation working I know who to call :) ... yeah! Thanks for the offer of the manuals I think I have all the ones for this machine. I will certainly look into whether something is bumping into the drum surface though. I do have a new whole transfer belt assay, I've just not the cleaning unit for it so, reluctant to put it in without renewing that too.

Does anyone know if the TB assay from a c5501 can be used in the c7000, I know they made a few tweaks in the upgrade, but will it work well enough that if I put it in the c7000 it will at least work, so I can then rule in/out the TB?

Synthol: Thanks for the pointer of the fuser, I hadn't thought to check that as I was convinced it was in process. Having checked it, there are a couple of marks but they don't correspond to the marks on the paper. I do have a spare fuser on the bench, so will finish rebuilding it and swap over to rule out that part.

blackcat: Oh yes those cheeky little blighters. Yes I have removed those, I have a little pile on the machine to remind me, and yes I too have forgotten to remove them in the past!! Yes indeed the distance corresponds to the drum circumference, which is why I initially changed the drum, but still get the same mark irrespective of the drum installed.

It's just such a weird mark, as if someone is pouring a liquid down the drum, but of course it's in the wrong direction...

Thanks again, most appreciated.
Mark

Toxic
07-13-2021, 09:48 AM
I dont see good from photo, is that mark only one color (black) or is it mixed color?
Which drums you use , i remember long time ago we all have problem on C5501 and DU-102C with cleaning blade factory problem?
It is little confusing you said repetition mark is 186-196mm, is it really changing distance, it should not if you measure from mark start point to second mark start point?
I would try to put other developing unit.

Failed mechanical part.
・Approx 188mm pitch: Damage on the drum surface.
・Approx 251mm pitch: Damage on the fusing belt
・Approx 53mm pitch: Developer conveyance failure of developing sleeve.
・Approx 95mm pitch: Soiled second transfer roller

tsbservice
07-13-2021, 10:03 AM
I dont see good from photo, is that mark only one color (black) or is it mixed color?
Which drums you use , i remember long time ago we all have problem on C5501 and DU-102C with cleaning blade factory problem?
It is little confusing you said repetition mark is 186-196mm, is it really changing distance, it should not if you measure from mark start point to second mark start point?

Failed mechanical part.
・Approx 188mm pitch: Damage on the drum surface.
・Approx 251mm pitch: Damage on the fusing belt
・Approx 53mm pitch: Developer conveyance failure of developing sleeve.
・Approx 95mm pitch: Soiled second transfer roller

@Toxic
On Mark's picture it looks like 186mm distance but yeah pretty close should be the drum.

@Mark
49685

raplma
07-13-2021, 12:58 PM
The mark is only K black, there is no CMY.

I mentioned that the spacing is variable, that would be because the shape of the mark varies each time, so there isn't a set datum to measure each mark. But they will be 188mm so yes the drum has something to do with it, and indeed was why I initially swapped the drum, but changing the drum has no effect. The drums are DU104's, yes we had the issue with the DU102's back in the day and have since only used 104's even on the c5501's and c6501 machines we had.

The strange aspect for me is that the mark is different each time, it isn't a consistent mark... could the TB be flapping - for want of a term - hence asking if a c5501 unit could be used.

49688

raplma
07-13-2021, 06:21 PM
Minor update
I can rule out the fuser as in swapping it the mark is still there.
I have been panic stopping the machine and the mark has always has just passed on to the paper, so will try again tomorrow to see if I can stop it when it is on the drum or TB.
FYI the mark gets progessively bigger and more pronounced the longer the job runs, stop and restart and the mark resets as it were, run a single sheet at a time and the mark is bearly visible...curious.
Many thanks for your suggestions and advice, most appreciated.
Mark

tsbservice
07-13-2021, 06:48 PM
Mark when you print CMY separations from Service mode is the defect present? If not that should rule out(at least that's my theory)TB and leaves only black drum/dev and surrounding as possible culprit.

Synthohol
07-13-2021, 07:43 PM
ive seen the coronas vibrate causing drum contact, you normally will see a kind of grid pattern but try swapping coronas around, see if the issue changes.

blackcat4866
07-14-2021, 12:35 AM
Similarly I was going to suggest swapping cyan and black drums. I'm still stuck on drum cleaning. =^..^=

raplma
07-14-2021, 09:25 AM
Morning all...
Thanks again for your replies, most appreciated.

tsbservice: The mark remains irrespective of the job sent through, CMY separations, no image anything. So yes so I agree, it's unlikely to be TB related.

Synthohol: Ideed, this is where I started when the problem first occurred, replacing the drum and corona with new items. But I think you and blackcat have given me the next thing to try, I know the drums/coronas of the CMY are fine, so as suggested swap them over and see what happens. The vibration concept I'd not thought of, so if swapping doesn't change anything, which I suspect it won't, looking into whether something could causing an oscilation of the drum/corona is a great idea, and kinda makes logical sence as to the shape of the mark, and why it gets more pronounced as oscilations by nature amplify.

Thanks again
Mark

raplma
07-14-2021, 01:29 PM
Sorted!...he says while grasping for some wood...just need to run a full job to make sure.

and the winner is....

Well not totally sure TBH.

I liked the suggestion of an oscilation causing the mark, so checked the drum shafts for any signs of play in the motor housing bearings, after all this is a high miler, but nothing of note. As suggested I swapped the cyan/black drum and corona's over, and ensured that they were snugly seated so that they couldn't oscilate. However...what I also noticed is that the TB assay didn't sit smoothly into it's support blocks when re-installing, you know how it usually just drops in, so cleaned them out put it all together, ran a load of test pattern sheets through and 200 sheets later no mark on any of them.

So, it could have been the drum/corona, or it could have been the TB oscillating on a bit of git in the groove, who knows.

What I do know is as usual you've come up trumps, so massive thanks for throwing ideas and suggestions at this, most grateful!

Until the next issue :)

Mark

blackcat4866
07-14-2021, 02:15 PM
Congratulations! Thanks for sharing. =^..^=

tsbservice
07-14-2021, 02:15 PM
I would like to steal (well temporarily) from BC saying 'Congratulations on your success'!
Anyway I have no doubts from the beginning :)
Mark it is real pleasure for me to read your posts. Much appreciated we have people like you here.

raplma
10-11-2021, 09:26 AM
Just a quick update on this for the record...

Guess what the marking came back again.
So, not knowing exactly which of the various things I had done actually appeared to fix it, I was kinda back to the start again.
Re-reading this thread I came back to what Synthohol had remarked about oscillation coronas.
As it turns out, it would appear to be this very thing. I noticed on the corona I had swapped before there was a very slight grazing of the shiny surface on the side that is towards the rear of the machine.
When you remove the coronas behind them at the front and back are two white sprung positioning/locating posts. Looking at all of them, it was clear some had been replaced in the past. And the rear one was looking rather off colour and tired. As the plastic housing was fine, I simply replaced the spring inside, and guess what, the mark was gone.
Funny thing is, I have not been able to locate the part in the parts manuals, can't find them anywhere, and I'm pretty familiar with the parts diagrams for this generation of machine.
Anyway run 50k sheets since and no marking...so here's to hoping I have cracked it this time.

So thanks again is in order!

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