bizhub 751 Copies Dramatically Lighter than Prints

[MFPs R Now PCs]

We have a bizhub 751 in the field that dramatically decreases the darkness/density of the letters on documents when making a copy. The exact same document when Printed looks fine. Is there a way to permanently fix this in “Tech Mode”? We could change the end user side via Density and/or Background Removal, but isn’t that “cheating”? (Or is that the only way to fix it)?


A New Drum/Developer change has already been done less than a month ago.

Please Help?!

[scottybbb]

Have you tried cleaning the optics.

[MFPs R Now PCs]

Have you tried cleaning the optics.

I guess I should have mentioned that we also have cleaned the Optics, Mirrors and CCD Lens. (oops)

[ZOOTECH]

We have a bizhub 751 in the field that dramatically decreases the darkness/density of the letters on documents when making a copy. The exact same document when Printed looks fine. Is there a way to permanently fix this in “Tech Mode”? We could change the end user side via Density and/or Background Removal, but isn’t that “cheating”? (Or is that the only way to fix it)?


A New Drum/Developer change has already been done less than a month ago.

Please Help?!

Don't know much about KMs, but is copy mode perhaps in "Toner Save" condition verses print mode in normal?

[WetPaper]

Did you try both off the glass and the adf? Was there a difference?

There are KM models where you can adjust the ADF density separately from the glass but I can't remember if the 751 is one of those. This would be cheating of course.

Has the CCD or Image Control Board been ruled out yet?

[MFPs R Now PCs]

Overnight it's now printing really light, even the Machine Management List is Very Light. I cannot seem to find the "Troubleshooting" Section in the Manuals "Field Service" or "Theory of Operation" for Copy/Print Quality Control (i.e. Light Print/Dark Print/Lines/Shaded Background/Dots on Page etc, etc.. like there is for ANY C Series Machine C451/C550/C650) Could someone point me in the right direction for finding these sections in what Manual, please?

[Zackuth]

You mentioned drum/developer change. Have you also done the transfer/seperation wire and cleaning unit changes, charge grid maintenance?

[CraigW]

If you take the dev unit out and spin by hand using the large white gear .... do ALL of the other gears (in stirring section) spin as they should ??

If those smaller gears get worn it cannot add toner to dev unit.

[ZOOTECH]

If you take the dev unit out and spin by hand using the large white gear .... do ALL of the other gears (in stirring section) spin as they should ??

If those smaller gears get worn it cannot add toner to dev unit.

OP said prints ok, just copies are light.

[Luther]

Like above said make sure the dv gears are not worn down, also make sure the sensor under the drum is not dirty

[MFPs R Now PCs]

The sensors underneath the drum are still clean. All of the processes indicated in the Adjustment Section of "Field Service" manual for replacing the drum were performed at the time of replacement.

I tore it apart again today and reinspected/cleaned everything, all charging units got cleaned, re-powdered drum and blade too. All gears on the developer are turning properly. Now prints are definitely dark again but everything is shadowed on the trailing edge. I did notice this before starting today but now it's very pronounced. Getting a secondary tech onsite. This WILL be resolved! Ha, ha.

As far as original post prints vs copies on too light: It started with only copies but in 1 day before I got on-site myself it now includes anything, even prints...?

[CraigW]

Also for light a couple of days ago I had a 601 light, and found the spring out of place on the little black cover that closes when you remove the drum carriage. Right near the front.