Bizhub 750 drum scratches

**Will** · 01-26-2012

Have 2 different Bizhub 750's that have prematurely developed scratches on the operator side or front side about 2 inches in from the end, and both machines seem to have the same type of scratches in the same area. It ends up being on the bottom inch of an 8.5x11 sheet running thru the machine landscape direction.

Looks as though something either in the drum carriage or transfer assembly is rubbing against the drum causing scratches around the circumference area. Checked all around drum carriage and transfer guide and corona and can't see anything touching it. Anybody ever see this, need suggestions???

**scottybbb** · 01-26-2012

Check mylars on the end of the transfer/separation corona unit.If the mylar is worn thru the metal of the corona unit will scratch the drum.

**Will** · 01-26-2012

Thanks but checked them and seem fine.

**suomi** · 01-26-2012

Buy new >>57AA R715 00 TRANSFER SEPARATION UNIT

**EarthKmTech** · 01-26-2012

Originally Posted by suomi

Buy new >>57AA R715 00 TRANSFER SEPARATION UNIT

Yep, throw it out even if it looks good. The threadlock on the guide plate loosens and the guide then comes into contact with the drum due to vibrations turning the screws.

This cannot be adjusted in the field and must be replaced.

**Synaux** · 04-01-2014

Originally Posted by EarthKmTech

Yep, throw it out even if it looks good. The threadlock on the guide plate loosens and the guide then comes into contact with the drum due to vibrations turning the screws.

This cannot be adjusted in the field and must be replaced.

I just ran into this.
At first I thought it was a bad cleaning blade and was about to install it, but when I inspected the old (but almost new) cleaning blade I used my magnetic screwdriver and it pulled off the reside off the blade. So I thought it was developer; however, I now think it is actually metal shavings...?

In fact, the metal area next to the Transfer Guide Roller was actually worn down (its a little over exposed in the picture, but its there). It destroyed a drum in about 17k hits and immediately caused a very fine line in a new one after only ~100 prints.
Untitled-1.jpg Untitled-2.jpg

I do see that the Drum Protection Mylar (56AA-1784-0) is broken in the corner on the worn side; however, it doesn't look like replacing the mylar will be sufficient by itself.

*Edit* The screws with the blue thread lock have worked loose...

Also, as you guys can see in the photo, it is dumping toner on the Transfer Separation Unit on the worn end and a tiny bit on the other edge too--this causes dirty edges on the paper (hardly noticeable on individual sheets, but blatant when looking at the edge of a stack of prints).
Any ideas for this other than the cleaning blade (which is almost new, but will be replaced regardles).

I very well may have never noticed this without this forum--thanks everyone!

**CraigW** · 04-03-2014

That lock solution they used was worthless.... every one of those plates came loose and would rise up.

**mrwho** · 04-03-2014

I'm not sure if this happened to me with a 750 or a 920, but slowly raise the corona and make sure the grooves fit into the holes of the drum unit. Sometimes they will not and the corona will be tilted in an awkward position (though I'm not sure if twisted enough to scrape the drum).