[CQ] C6501 with Halo/Shadows on CMYK Text

[mrwho]

Hello there.

Printing in CMYK, black text shows a noticeable halo or shadow around the letters (if it was typed with Bold) but not on pure K text.

Here's an example:

halo.jpg

The upper line is K text; the lower line is CMYK text. On the computer screen all text looks the same, you can only see the difference using the color picker (upper text is something like 33,33,33 RGB and lower text is something like 00,25,33 RGB, if memory serves me right), so the machine treats the upper line as pure black and lower line as composite black.

So the shadow or halo around the text is the real problem. I've already exchanged all the parts on the fusing unit and transfer unit that exceeded PM; also pulled out the registration sensor section and cleaned it thoroughly; ran all the gamma adjustments after cleaning optics; tried different belt speed settings; nothing worked.

Couple of questions:

- Both the black developer and black developing unit are beyond PM, but not that much - the K developing unit is not throwing out developer and copy uniformity is okay (not perfect, but okay) so apparently the black developer is nice. I've had to change black developer before because of lack of quality, but it never showed this symptom, so I've discarded it so far, but could I be wrong? Could this be caused by the black developer and/or the black developing unit?

- Besides this, what else could cause this?

Thanks for your time!

[Texers]

Re: C6501 with Halo/Shadows on CMYK Text

hi,
if you haven't tried this already..

► Full color mode (At the 1st transfer, all colors are pressed)
Symptom occurrence position is 1st transfer unit.
[Cause]
Toner attachment amount is too much.
[Solution]
Since the symptom becomes noticeable by the slight change of density, BT proposes the
following step by step method to optimize toner attachment amount.
After performing each step, check whether the symptom appears or not.
1. Access the Covered Margin Fine Adjustment and if the adjustment value is minus value,
check whether the symptom occurs with the default value.
If the minus value was entered, reset to the default value (+/-0).
[Service Mode]=> [02 Process Adjustment] => [02 Process Fine Adjustment] =>
[01 Covered Margin Fine Adjustment]
NOTES:
*1: The adjustment value is reflected after performing Automatic Gamma adjustment.
*2: If adjustment value is increased too much, carrier attachment or void occurs.
Therefore, check the image using test pattern
*3: If the + value is already entered at step 1, go to step 2 then step 4.
2. If the step 1 is not enough,
Decrease Bk maximum toner quantity adjustment value (Start check from [-2])
[03 Machine Admin. Setting] => [01 System setting] => [05 Expert Adjustment] => [06
Process Adjustment] =>[03 Toner Quantity/Exposure]=> [Maximum Toner Quantity]
NOTE:
* Since the maximum Bk density decreases, check the image density using test pattern.
3. If the step 2 is not enough,
Access Covered Margin Fine adjustment and increase Bk adjustment value.
Start check from [+3]
[Service Mode]=> [02 Process Adjustment] => [02 Process Fine Adjustment] => [01 Covered
Margin Fine Adjustment]
4. If no improvement is observed after step 1 and 2,
check the following points of 1st transfer section of intermediate transfer unit:
► Whether shaft holder is damaged.
► Whether pressure spring is moved from normal position
5. If no abnormal is found at the step 4, replace intermediate transfer unit.


for me, usually step 2 does it..
hope it helps.

[mrwho]

Re: C6501 with Halo/Shadows on CMYK Text

hi,
if you haven't tried this already..

► Full color mode (At the 1st transfer, all colors are pressed)
Symptom occurrence position is 1st transfer unit.
[Cause]
Toner attachment amount is too much.
[Solution]
Since the symptom becomes noticeable by the slight change of density, BT proposes the
following step by step method to optimize toner attachment amount.
After performing each step, check whether the symptom appears or not.
1. Access the Covered Margin Fine Adjustment and if the adjustment value is minus value,
check whether the symptom occurs with the default value.
If the minus value was entered, reset to the default value (+/-0).
[Service Mode]=> [02 Process Adjustment] => [02 Process Fine Adjustment] =>
[01 Covered Margin Fine Adjustment]
NOTES:
*1: The adjustment value is reflected after performing Automatic Gamma adjustment.
*2: If adjustment value is increased too much, carrier attachment or void occurs.
Therefore, check the image using test pattern
*3: If the + value is already entered at step 1, go to step 2 then step 4.
2. If the step 1 is not enough,
Decrease Bk maximum toner quantity adjustment value (Start check from [-2])
[03 Machine Admin. Setting] => [01 System setting] => [05 Expert Adjustment] => [06
Process Adjustment] =>[03 Toner Quantity/Exposure]=> [Maximum Toner Quantity]
NOTE:
* Since the maximum Bk density decreases, check the image density using test pattern.
3. If the step 2 is not enough,
Access Covered Margin Fine adjustment and increase Bk adjustment value.
Start check from [+3]
[Service Mode]=> [02 Process Adjustment] => [02 Process Fine Adjustment] => [01 Covered
Margin Fine Adjustment]
4. If no improvement is observed after step 1 and 2,
check the following points of 1st transfer section of intermediate transfer unit:
► Whether shaft holder is damaged.
► Whether pressure spring is moved from normal position
5. If no abnormal is found at the step 4, replace intermediate transfer unit.


for me, usually step 2 does it..
hope it helps.

Thanks for the hints. I tried messing with K toner density, but not by much, and since it didn't show any difference, I discarded it. I'll try those tomorrow.

As for the shaft holder and spring, which ones are you refering two? The two springs that stretch the transfer belt? And which shaft holder?

Thanks!

[Texers]

Re: C6501 with Halo/Shadows on CMYK Text

As for the shaft holder and spring, which ones are you refering two? The two springs that stretch the transfer belt? And which shaft holder?

Thanks!

1st of all.. try to run some test charts through.. see how those are coming out.. before starting to do anything.. make sure is not a file issue. also you can try preflight the job.

after that..

shaft holder and spring is: A03U R745 00 POWER SUPPLY BLOCK D ASSY. sometimes i find it damaged and can cause these kind of issues.
also worth to check if : 65AA -273 0 TENSION PLATE REAR CAULKING is/was fitted properly (both marks touching the frame - very important) - this can cause this fault as well as some colour registration issues.
if you start playing with toner density, i would advise you to run auto gamma after each step u go up / down. if it shows any improvement do a proper m/c setup as you may end up with colour variations.

may not have anything to do with your problem but check rendering intent on the rgb channel, eventually the whole colour flow.
though, now looking with a magnifying glass which colour is faulty? k or c?

[mrwho]

Re: C6501 with Halo/Shadows on CMYK Text

1st of all.. try to run some test charts through.. see how those are coming out.. before starting to do anything.. make sure is not a file issue. also you can try preflight the job.

I did that roughly after I first saw the problem (and after a couple of tries at solving it with cleaning and adjusting), and long before posting here. I first thought it could be a rip problem when the customer showed me the above example (those lines are part of the same page), and I dismissed that once I figured out it happened on CMYK text and not on K text.

shaft holder and spring is: A03U R745 00 POWER SUPPLY BLOCK D ASSY. sometimes i find it damaged and can cause these kind of issues.

I'll check that. I never had to replace those before, so it's no wonder I'm stuck if a problem is caused by it. Is it possible to confirm if that part is indeed the culprit by looking at it - will it have any hairline cracks or something like that?

also worth to check if : 65AA -273 0 TENSION PLATE REAR CAULKING is/was fitted properly (both marks touching the frame - very important) - this can cause this fault as well as some colour registration issues.

Thanks for the tip. It's in place - I make sure it is like that every time I need to take out the transfer belt. Had my handful of belt problems when I first started servicing these machines just because that part wasn't exactly in place.

if you start playing with toner density, i would advise you to run auto gamma after each step u go up / down. if it shows any improvement do a proper m/c setup as you may end up with colour variations.

It did indeed show improvement, but didn't disappear completely. I've just ordered the HV part you pointed me, along with K developer and K developing unit just because they're both past life and I'm now almost sure the problem is related to toner density.

I'll keep you posted. Thanks for the tips!

[eifling]

Re: C6501 with Halo/Shadows on CMYK Text

Are you positive its the engine and not the graphics and or rip? Reason I asked I have seen similiar issues where in the pdf it looked crisp but for what ever reason because fuzy in print. Tried it on 3 different machines to the same effect.

Fiery or Creo?

[Texers]

Re: C6501 with Halo/Shadows on CMYK Text

I'll check that. I never had to replace those before, so it's no wonder I'm stuck if a problem is caused by it. Is it possible to confirm if that part is indeed the culprit by looking at it - will it have any hairline cracks or something like that?

yea, you should be able to tell if is broken or not.. usually is due to heavy handed engineers. in my cases 1 of the hooks that keeps the holder in place was broken - that gives a bad position on 1st transfer roller and/or vibrations. by setting the m/c to push all 1st transfer rollers against the belt will reduce vibrations especially when u print on thick stock 250+gsm. however that can give you other headaches..

also related to that area, when i do pm, i clean the tension rollers (silver ones). i've noticed toner/dust start to build up on them and that damage the belt on the inside - results in bad transfer. and it seems the m/c performs better and is more stable.

It did indeed show improvement, but didn't disappear completely. I've just ordered the HV part you pointed me, along with K developer and K developing unit just because they're both past life and I'm now almost sure the problem is related to toner density.

what i found was that i had to go quite extreme with the density in order to cure the problem and from there was just a fine tweaking backwards.

may worth to check, in m/c admin - process control, you can set how much toner and how often to be added. it could be a wrong setting there.
also you could check how is the image on the drum.. if fault is there then it could be a developing/TCR issue

I'll keep you posted. Thanks for the tips!

glad i could help!

[Texers]

Re: C6501 with Halo/Shadows on CMYK Text

Are you positive its the engine and not the graphics and or rip? Reason I asked I have seen similiar issues where in the pdf it looked crisp but for what ever reason because fuzy in print. Tried it on 3 different machines to the same effect.

Fiery or Creo?

had some halo on KM5501+IC408, in thin white text within solid colours caused by some 3rd party imposition software. as soon as i tried the fiery imposition (even demo one) fault went away and had very nice crisp white text. but this is something bit different..

[mrwho]

Re: C6501 with Halo/Shadows on CMYK Text

Well, that should be easy enough to test - just run some copies with a text original in full color should be enough to see whether it's a controller problem or not. I'll keep you posted!

[jma676]

Re: C6501 with Halo/Shadows on CMYK Text

Hello there.

Printing in CMYK, black text shows a noticeable halo or shadow around the letters (if it was typed with Bold) but not on pure K text.

Here's an example:

[ATTACH=CONFIG]19850[/ATTACH]

The upper line is K text; the lower line is CMYK text. On the computer screen all text looks the same, you can only see the difference using the color picker (upper text is something like 33,33,33 RGB and lower text is something like 00,25,33 RGB, if memory serves me right), so the machine treats the upper line as pure black and lower line as composite black.

So the shadow or halo around the text is the real problem. I've already exchanged all the parts on the fusing unit and transfer unit that exceeded PM; also pulled out the registration sensor section and cleaned it thoroughly; ran all the gamma adjustments after cleaning optics; tried different belt speed settings; nothing worked.

Couple of questions:

- Both the black developer and black developing unit are beyond PM, but not that much - the K developing unit is not throwing out developer and copy uniformity is okay (not perfect, but okay) so apparently the black developer is nice. I've had to change black developer before because of lack of quality, but it never showed this symptom, so I've discarded it so far, but could I be wrong? Could this be caused by the black developer and/or the black developing unit?

- Besides this, what else could cause this?

Thanks for your time!

[florina]

Re: C6501 with Halo/Shadows on CMYK Text

IT happened to me too when printing PDF documents with text when accidentally selected "print as image" instead of "let printer determine colors" in adobe print window

[tulintron]