Xerox 7800 - Light Gray Repeating Dots?

[Matthew Barkowski]

I originally thought these marks were because of the roller assembly but after replacing them I realized I was mistaken. Does anyone have any idea what might cause these?

I read some posts that it might but the "IBT belt". Does that sound right. See pics.

https://www.colorprintingforum.com/threads/xerox-phaser-7800gx-repeating-marks.16607/

 

[OkiTech]

hi, take a 11x17 sheet, print something that dot would show up and post.
Simplest way to do determine the issue is to measure the distance between defects and compare the to the circle length or the components. I can not determine that out of your pictures.

 

[I Gen]

Did you ever fix this? It looks like the transfer roller, fuser assembly or ibt belt.

 

[Matthew Barkowski]

I replaced the IBT belt assembly and that worked for about a year and a half - although if that was actually the correct solution is speculation. The marks don't seem to line up with anything on the repeating defects (printed on 11x17). I'm going to replace the fuser assembly 1st (I have other repeating marks that are 94mm so for sure the fuser assembly) then likely replace the IBT belt assembly again assuming it does not stop. Frustrating to say the least. Let me know if you have any suggestions! Will likely replace the belt cleaner as well...

 

[Biggs]

If you look at the dots under a loupe, are they composed purely of black?

are they always along a linear path like in the picture?

 

[Matthew Barkowski]

Yes always linear and does not match up with anything on the "Repeating Defects" page. I don't own a loupe (magnifying glass), but from the naked eye, they appear gray with no other colors. Another interesting fact - they'll mostly erase if you take a good eraser to it. If I look in the printer on the ibt belt, I see the marks - they appear translucent on the belt if that makes sense. Thinking I need another ibt assembly, although I replaced mine 1.5 years ago.

 

[Matthew Barkowski]

And correction on the previous post - I have other dots that are 95mm, not 94, indicating an imaging unit needs replacement, not the fuser assembly. s

 

[Biggs]

My apologies, I missed your reply.

it could be black developer leaking onto the belt. Take a look at the black unit and see what you can find.

if it’s only black on the belt/paper it must be coming from the black imaging unit. My bet would be the developer housing is compromised in some way, or the developer within it is old and needs to be replaced

 

[OkiTech]

Hi guys. As far as "I replaced Belt 1.5 years ago" , while physical age of the supply items is also important, main identifier is amount of pages it had run. So if you have issues with belt after, lets say 20,000 pages it would be odd but if you racked up 100,000 impressions in that 1.5 years, I'd say it is completely expected that new one might be need.

 

[OkiTech]

Now, printer talk. Rule number 1: please state print count of your printer. If we're talking about printer with 30-40k impressions, it could be different set of problems from printer with 200-300K pages on it. I remember fighting 2 grayish dots in 7800 or 7500 and they went away only with belt replacement but it was a while ago, like really a while. I guess one way to determine if it is a problem with belt is to find those dots on it, clean them off with dry qtip and look with eye-loupe if there are some kind of damages, craters may be, that collect toner dust and re-deposit that on to paper.
There is nothing much in that printer that can produce gray, issue with any of the colors are likely to be distinguished C or M or Y or K, in my opinion, the only way it can be gray is if it picks up dust out of belt cleaning section where all colors are mixed and mixture of gray can exist

 

[Matthew Barkowski]

Thanks for all the responses! I ended up replacing the black imaging unit and the dots disappeared until recently (approx a year). I'm getting them again. To answer the questions above, my 7800 has 106,000 total impressions on it, which I would guess 30-40K would have been since I replaced the IBT belt assembly. Also, I have attached my supply sheet to show how worn out my components are (not very).

 

[Matthew Barkowski]

More images. This one zoomed in. You can see it has a red tint to it. Oddly - I have noticed it seems to be a problem if the temperature is below 65 degrees Fahrenheit in the house. When it warms up, it seems to correct itself. As you can see, still can't figure out what it really is since 2019 - I just work around it

 

[Matthew Barkowski]

The other thing I would say - I am using 130lb cardstock- the absolute thickest the printer can handle (per specs).