M8124cidn service manual or defect sheet.

[fluffybunnyuk]

Hi,
I'm trying to work out why a line occurs on the reverse side/manual duplex, 2cm from the top.

the service manual would help. I'm not entirely sure if its paper not taking the charge, or the fuser or whats causing it.

[Ropariva]

So…..based on your scant information and no photo, are you saying it occurs on the back of a single sided document? By “top” do you mean leading edge? Is it blurry or a sharp line. Happens in black or full colour. How many prints has the machine done? Does it happen on A4 and A3? What have you done so far? Swapped drums around?
When you have a problem like this you have to find ways of eliminating parts of the machine from the equation. Have you stopped the print part way through and examined the transfer belt and fuser for example.
I teach my techs to try and have answers to all the questions I would ask them before they call me. Often doing this they find the answer to their problem.

[fluffybunnyuk]

https://ibb.co/VcxVq95w

It occurs on A4 1200dpi fine, manual duplexing on the second pass. its a fading line in colour only that looks like the machine needs a drum refresh. Except the drums been refreshed, and a couple of dev-clns to make sure enough toner is in the developer,. the machines done 200 pages. the print is from the MP tray as its 220gsm, and a selection of papers have been tried all with the same effect.
drop it down to 80 or 160gsm and its fine. Which lead me to assume if its not the drum then maybe its a fusing issue. So i tried slowing the print down and it still happened.
the defect is 2cm from the leading edge, which doesnt correspond to the defect chart, so it takes me back to the drum.
what makes me frustrated is that its an intermittant problem.
Not sure i'm making progress.

[Ropariva]

I’d suspect the paper has a deviation in it’s surface after the first run. Ie, a dip at that point that is causing poor transfer on the second side.
You can duplex thick paper from the trays. Have you dried doing that instead of manual duplex? For this kind of document it would be preferable.
you can also try loading paper landscape and see if that works

[KYO_OEM]

Possible static charges from the paper due to the higher secondary transfer voltage required for 220g.
This generates a countervoltage on the belt, which is then transferred to the drums.
This is also reflected in the lower voltage required for 80 or 160g.
Less surface on the drums >> stripes.....
Problem of this media type, open brand new paper packet and try again.
Check grounding from plate discharger on 2nd transfer unit.

[fluffybunnyuk]

Thank you both of you. Much appreciated.

[Dark Helmet]

Is that mark going front frame to rear frame or lead edge to trail edge?

[fluffybunnyuk]

its ok, the solution is cooling. somehow the laser printer is overheating. never seen that before in an A3.
50 sheets and its cooked.
meanwhile my HP A3 laser churns out hundreds without cooking itself.