what causes dark background on copies, but scans and prints look fine?

[sbtiti]

I am working on a Workcentre 3635mfp and sometimes the configuration report that prints after power on will be all dark, but usually a test print such a Customer Assistance Report, will look fine. When I copy a page, the copy comes out with a light gray background at the top 2/3 of the page and dark gray on the bottom 1/3.

I have performed scans and they look fine, so the problem must not be with the scanner. The toner/drum cartridge is brand new. I have cleaned all the spring contacts to the HVPS and that did not help.

I am having trouble understanding what might be happening here, and not sure what part to replace first. Any help from other forum members would be greatly appreciated!! Thanks.

[Phil B.]

Re: what causes dark background on copies, but scans and prints look fine?

I am working on a Workcentre 3635mfp and sometimes the configuration report that prints after power on will be all dark, but usually a test print such a Customer Assistance Report, will look fine. When I copy a page, the copy comes out with a light gray background at the top 2/3 of the page and dark gray on the bottom 1/3.

I have performed scans and they look fine, so the problem must not be with the scanner. The toner/drum cartridge is brand new. I have cleaned all the spring contacts to the HVPS and that did not help.

I am having trouble understanding what might be happening here, and not sure what part to replace first. Any help from other forum members would be greatly appreciated!! Thanks.

look at the development unit....

[sbtiti]

Re: what causes dark background on copies, but scans and prints look fine?

If it were an issue with development, why are only copies effected? Unit reports look good and printing from computer looks fine too. Only the copies seem to have the dark grey background. I thought it must be in the scanner, but when I just scan the same original, the image looks fine.

I can't make logical sense of this problem. I guess I might see how a bad power supply might cause this issue. Any further ideas would be appreciated. Thanks.

[rockdude]

Re: what causes dark background on copies, but scans and prints look fine?

I am a little confused??

First you say the config page has the problem (which is NOT a copy) then you say the customer assistance page prints okay.

But when "Phil B" suggests "Development" you say it "Only" applies to copies??

If it happens on the config page on startup it's happening on more than just "copies".

Is the graying consistent? (If you make 10 copies do they all have the same graying?)

Run 10 config reports do they all have the same problem?

If it's inconsistent you may be right with the HVPS if it's not I would rethink the development section.

[Phil B.]

Re: what causes dark background on copies, but scans and prints look fine?

If it were an issue with development, why are only copies effected? Unit reports look good and printing from computer looks fine too. Only the copies seem to have the dark grey background. I thought it must be in the scanner, but when I just scan the same original, the image looks fine.

I can't make logical sense of this problem. I guess I might see how a bad power supply might cause this issue. Any further ideas would be appreciated. Thanks.

go back and READ what you first said was the issue.

SOMETIMES these machines DO NOT MAKE LOGICAL SENSE

[sbtiti]

Re: what causes dark background on copies, but scans and prints look fine?

This is why it is so hard to determine the cause. The initial, auto printed config report, is the only report that comes out dark (sometimes). The copies always have the problem on the bottom third of the page. Except for the copies always showing the issue, it seemed like a thermal issue because the initial report would come out perfect if the copier had been on for a while and then turned off and on then the auto report came out looking perfect. I might assume there are two different problems that need resolved, but I would like to concentrate on the consistent issue with the copies first: Why do reports and prints look fine, but copies get a grey background when the scanned image also looks fine?

[Milo Wilson]

Re: what causes dark background on copies, but scans and prints look fine?

Sounds like the light bar in platen glass area. When you scan, the light bar moves to a fixed location and paper moves across. When you copy off the glass the light bfast moves and the paper is stationary. The lamp is probably fluctuating in brightness when moving.

[rockdude]

Re: what causes dark background on copies, but scans and prints look fine?

If that were true, then just to test. Make copies with the ADF.

Since the scan lamp doesn't move during ADF copies it would either prove of dispovewhat you said.

[sbtiti]

Re: what causes dark background on copies, but scans and prints look fine?

Thank you for the ideas. Keep them coming, please. I have copied using the ADF and still have a grey background, but it is more evenly distributed down the page. The flat bed copies had a darker grey at the bottom third of each page and I don't see that change on the ADF copies but they still have the lighter grey background that the print outs do not.
It is almost like the HVPS is unable to provide the proper static charges when the scanner is being used. It might be time to see if a new HVPS solves this issue, but my client has not authorized it yet.

Thanks again for your assistance and help.

[Milo Wilson]

Re: what causes dark background on copies, but scans and prints look fine?

I would lean towards the scanner lamp itself as being the problem. Either clean it and the mirrors in the scanner or replace it with a new one

[sbtiti]

Re: what causes dark background on copies, but scans and prints look fine?

Thanks for the help. I will check the lamp and mirrors, however, I would think the scanned image would also show the problem if caused by the scanner unit. This may take me a few days to determine the outcome, but I will report back to this thread. Thanks again.

[sbtiti]

Re: what causes dark background on copies, but scans and prints look fine?

I have found that scans have a slight grey background, but nothing like the copies that seem worse the last 1/3 of the page. This darker 1/3 happens when using the flat bed glass for copies. I noticed that when the scan bar gets 2/3 the way down the page that the printer motor startup so it appears that this might be a clue to why the bottom 1/3 is darkest. It sounds like a power supply issue. What do think? Would you think the main power board or the high voltage power supply?

Thanks for any further help you can provide.

The scanner light is bright and even through the scan process.

[Phil B.]

Re: what causes dark background on copies, but scans and prints look fine?

I have found that scans have a slight grey background, but nothing like the copies that seem worse the last 1/3 of the page. This darker 1/3 happens when using the flat bed glass for copies. I noticed that when the scan bar gets 2/3 the way down the page that the printer motor startup so it appears that this might be a clue to why the bottom 1/3 is darkest. It sounds like a power supply issue. What do think? Would you think the main power board or the high voltage power supply?
Thanks for any further help you can provide.
The scanner light is bright and even through the scan process.

so when the engine starts ( vibration ) you notice the problem..

could the PCU or DEVELOPER move and cause bias problems?

if it isn't laser... could be dev unit from the vibration is causing contact probs.. the old oki 4545 ( toshiba engine )
would do it until i added foam to front cover inside

IF it does it on internal prints AND Copies it's NOT the scanner

[Milo Wilson]

Re: what causes dark background on copies, but scans and prints look fine?

the scanner lamp ribbon cable usually goes bad by getting cracks and when the carriage moves, the ribbon cable connections will fluctuate the power to the lamp.

[sbtiti]

Re: what causes dark background on copies, but scans and prints look fine?

Print jobs look fine and so do internal reports. Copies are the poorest, but scans also have a slight background shading problem. I have cleaned the CCD mirror and both sides of the scanner glass to no avail. I will inspect the scanner ribbon cable for any defects. Thanks for the ideas.