Old problem on C6500

[empiru]

Hang on guys, this is a tough one. So, we have this Bizhub Pro C6500 (3.000.000 copies) with a problem that has been going on for aprox. 2 years now.. If I print, let's say, an A3 sized paper with a full background (for e.g. Y 100, M 70, C 0, K 0) the print will come out with more yellow to the back of the machine than to the front; this is sometimes very annoying, there are orders that my collegues just can't print because of this. More details (and maybe tomorrow, I will scan a print-out) : changed ALL developing units, ALL charging coronas, ALL drums (of course, in 2 years I've done that several times), ALL developers, ALL WRITING UNITS, fixing unit, Transfer Belt Unit and ocassionaly only The Transfer Belt, Transfer Roller Lower. The machine does this on any stock, 80 gsm to 300 gsm. I did every possible adjustment, did all the adjustments for replacing parts, had the Minolta Techs visit us for several times with no results. Here is the interesting fact: we service other 3 C6500 and 2 of them ARE HAVING THE SAME PROBLEM these other 2 print slightly better as the first one.. I was just wondering, has anybody seen this on other C6500s? Are we the only ones having these problems? Thanks! I forgot to say, the size of the print-out doesn't matter, from A4 to 13 x 19 inch, no difference and also forgot to say, I changed 2 different Color Registration Assys too, but thanks to the new text editor, I can't go back in the text to modify, so...

[seeb]

Re: Old problem on C6500

Something maybe to try.

[empiru]

Re: Old problem on C6500

Something maybe to try.

Thanks! I forgot to say, I've done that too... sorry, I did so many things in 2 years with this machine, I can't think of everything right now But thank you any way! Now let me explain why this kind of "adjustment" won't work for me: The print-out has a different color (more yellow) only on a ~5-6 cm wide area, and as long as the sheet of paper is.. you'll understand better when you see the scan.

[richd]

Sounds like the distance between the coronas and drum surface needs adjusting, this is a common problem and there are plenty of info for your techs to get from km.
In service mode print test pattern 53, 1 at a time with a density of 40, measure the delta e value with a spectometer, in board and out board , the difference in value should be no greater than 2.
Adjust to compensate for this, if you can get it within a delta value of 2, its within spec and is a realistic achievement.

[empiru]

Re: Old problem on C6500

richd, thanks for the input; however, seeb suggested the same thing, I said I've done it without results..I'm the tech, I did everything I said and yes, KM has given me information about the distance between the corona and drum surface; after I tried it myself, it didn't work, a KM tech came and did the same thing with the same results.. that's why I said it's a tough one anyway, thanks for your support.

[richd]

No problem, couldn't download the attachment using mobile app !
Only thing left is changing the process carriage, could be skewed and wouldn't matter what you changed, would always get the same results ! A long shot but worth a go !
Good luck

[empiru]

Re: Old problem on C6500

You know what, I thought of that too and since you're the second person to think of that, I think I'll give it a try... I hope it's not too expensive, though...will see.Thanks!

[inutelkamo]

Re: Old problem on C6500

have you solve this problem?

We have encounter same type of problem..
We change 4 drums, transfer unit, corona, transfer unit, 4 developing unit and ofcourse with new 4 developers,
but still unsolve..

Until 1 day, as we were trying to see if what we can do, i have accidentally touch process adjustment at the paper size settings,
and for i dont know, i set the "SEPERATION DC" front and back to -25..

It solved the problem...

[empiru]

Re: Old problem on C6500

have you solve this problem?

We have encounter same type of problem..
We change 4 drums, transfer unit, corona, transfer unit, 4 developing unit and ofcourse with new 4 developers,
but still unsolve..

Until 1 day, as we were trying to see if what we can do, i have accidentally touch process adjustment at the paper size settings,
and for i dont know, i set the "SEPERATION DC" front and back to -25..

It solved the problem...

Thanks, I will try that too.. I'm not very confident it will work, but if you say it solved you're problem, I have nothing to lose.

[Ianizer]

Re: Old problem on C6500

I'm at a bit of a loss, Empiru.
Clearly, you've made reasonable effort to correct the problem.
I'd have looked at charge wires.

I don't know your firm's relationship with K-M, but they've been very responsive to us with sending a field engineer when necessary.
Might consider holding K-M's feet to the fire on this one...

-I

[empiru]

Re: Old problem on C6500

Well, our company has a very good relationship with KM... just like I said, they visited us for several times... but... I just think they don't know the solution either; I'm just being honest..

[seniortech]

Re: Old problem on C6500

Try replacing both of the process unit carriage rails. I had a similar problem a while ago, like you every thing was changed without any success. turned out the carriage rails were bent causing colours (especially yellow) to be slightly darker at the rear side, what caused this we never found out (maybe someone leaning on the carriage during maintenance???)

Good luck

[empiru]

Re: Old problem on C6500

Try replacing both of the process unit carriage rails. I had a similar problem a while ago, like you every thing was changed without any success. turned out the carriage rails were bent causing colours (especially yellow) to be slightly darker at the rear side, what caused this we never found out (maybe someone leaning on the carriage during maintenance???)

Good luck

That's a very good idea. Thank you! After all, those rails sustain a pretty big weight and can easily be bent... interesting, will try it for sure.

[inutelkamo]

Re: Old problem on C6500

Nice! very nice.. I never realy expect that the rail could effect the imaging system of the machine.. Good suggestion friend.. additional knowledge and parts to be check if incase i would encounter the same problem again..

[eifling]

Re: Old problem on C6500

We had the exact same problem with some jobs having yellow shading on the sheet even though there was not any yellow in the job.

For weeks our tech worked on it and eventually said it was humidity in the paper and messed with the settings but nothing was ever solved. He tried many of the things mentioned in this thread but in the end still stuck with humidity being the problem.

In the end we changed the Screening from Dot 1 to Line 1 and simple as that, problem solved.