[CQ] MP7500 black copies

[mrwho]

I'm looking at a MP7500 outputing black copies - completely black paper, not just overtoned or heavy backgrounded copies where you can faintly see the text. This machine is spitting out pitch black copies. I removed the toner bottle and, as the toner runs out, the black copies turn into gray copies, but I still can't see any text.

I've been checking around the machine settings and dismantled the entire charge assy (corona and the back of the machine) but no luck.

Any hints?

[Polo-022]

Charge corotron...maybe a broken wire!

[mrwho]

Before I posted this, I found the machine with a SC300 error and the wire was, indeed, broken. After replacing wire came the black copies.

Sorry for forgeting to mention this.

[aabarnes1]

You have a charge all over the drum, possibly caused by a faulty charge corona power pack or no drum earth. Can you try a pcu from another machine like a 5500 or 2051?Do you have any other sc codes logged?

[TonerMunkeh]

Could be the end blocks are shorting out. You got a spare corona unit from a Bellini, Katana or another Martini you can try?

[Fearless V K]

I believe you can energize the corona in sp mode. try it and you should be able to see it glowing if it is working. otherwise sounds like a bad power pack or contact somewhere.

[westonprawn]

Ive had this before and it was a stray paper clip shorting the charge pcb (Horizontal, rear of mc under scanner), Long shot I know but is definatley no neg charge on drum so everything is going over....

[Ricohtechguy]

Just put a new charge corona unit. Once they arc out and blow the charge unit is finished.

[spaceman99]

end springs (block) at the rear of corona assy bent or broken. I would change the whole assy.

[Masterchief]

ive seen this problem numerous times, all charge grid related problems. the springs are not contacting properly or the grid has arc'd completely and needs a whole new unit.

[kopirmaster]

when you change wire,do you get back plastic screew on charge corona,or you back metal screew,maybe this is your problem

[Fogonazo]

Re: MP7500 black copies

I have the same problem erratically, without a fault code.
I've made the following attempts diagnostic
I changed the corona charging by the crown of another machine
I changed the power supply unit revealing
I changedthe power of load
Ground the drum by hand with temporary wire cun

But the failure continues

[Herrmann]

Re: MP7500 black copies

You always said black "copies", how about the prints? Do a counter print, how does it look like?

To estimate, if the error is charge related or laser related, tape a part of the dust proof glass with black tape, is the sheet still completly black?

[Fogonazo]

Re: MP7500 black copies

The impression is black, on copy mode or printing mode.
Including printing of the counter.

Thanks for replying

[Herrmann]

Re: MP7500 black copies

ok, then do the "glass trick" as i described and see, what happens