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lead guitarist
intern
Joined: 03 Apr 2007
Posts: 123
Location: Texas
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 Posted: Wed Oct 22, 2014 4:17 pm Post subject: Black when cutting paper/dark background/black prints |
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Hello,
Weird thing here. Machine was giving intermittent black prints, solid black. everything was replaced! Drum, charge assembly, developer housing, all new developer bias pins and lubed with di-electric grease, swapped out charge harness, HVPS for charge -2.2 btw as measured from test points. Everything looks great! Swapped grid supply board. When cutting from the roll it gives a 100% black sheet, when printing a plot it's almost black but you can see the image through the blackness. I removed the grid screen and now I have a black and white print like I should. Although it's not what it should be!
I am at a loss and feel like I am running in circles. Been doing this kind of work for 30 years and I know it should be working at this point! What am I missing?? Ugg pulling my hair out!!! Any suggestions??
Lead Guitarist
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If it's too LOUD get some plugs!! |
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KipCody
medical school grad
Joined: 16 Jul 2013
Posts: 65
Location: Knoxville, TN
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| Posted: Thu Oct 23, 2014 11:18 am Post subject: |
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| Have you tried adjusting the current to the grid plate in service mode? I think it's sub mode 4 item no. 1b |
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lead guitarist
intern
Joined: 03 Apr 2007
Posts: 123
Location: Texas
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| Posted: Thu Oct 23, 2014 11:36 am Post subject: |
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No because the weird thing is when the charge assembly is in the machine without the grid it will print, not awesome but it prints! I had it working with all the parts in it, but took it apart again to clean an issue and then no bueno!
I have narrowed it down to the process unit itself, it just does not go in all the way as it should, shy by about a 1/4 inch for the ground tab to make contact with the charge assembly. The tab that is mounted on the L.E.D. head!!
I am getting closer!!!
_________________
If it's too LOUD get some plugs!! |
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TXReproShop
doctor
Joined: 04 Apr 2005
Posts: 300
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| Posted: Thu Oct 23, 2014 2:06 pm Post subject: |
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Had a similar issue with a 9000 a couple years back. I had cleaned the printhead by hand and somehow bent a very small corner of the copper down. It was touching the drum and causing all black prints.
While probably not your problem, it was something that we chased for several days. So I would say you are looking at a grounding issue. |
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lead guitarist
intern
Joined: 03 Apr 2007
Posts: 123
Location: Texas
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| Posted: Thu Oct 23, 2014 2:48 pm Post subject: |
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Seems that the charge assembly does not have enough clearance from the drum, shorting out the charge. Not sure why this is because that distance is fixed, and it explains why when we install a charge unit without the grid there is clearance!! Weird! I will kick it's little but into submission at some point!
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If it's too LOUD get some plugs!! |
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CHILLIN
doctor
Joined: 05 Oct 2006
Posts: 950
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| Posted: Thu Oct 23, 2014 3:06 pm Post subject: |
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| If the clearance between the main charge and drum is not correct. Check to make sure the counter wheels are sitting correctly against the drum in the groove not on the drum. Hope that makes sense. Also check the blocks the charge Assy mounts to. |
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lead guitarist
intern
Joined: 03 Apr 2007
Posts: 123
Location: Texas
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| Posted: Thu Oct 23, 2014 3:47 pm Post subject: |
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Thanks but I already checked those two things! In all reality it should fit correctly. As with a charge unit without the grid and grid hold downs, no problem except the print quality sucks!
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If it's too LOUD get some plugs!! |
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GRAPHICS-TECH
medical school freshman
Joined: 04 Jun 2014
Posts: 27
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| Posted: Fri Oct 24, 2014 9:24 am Post subject: |
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| wires for corona unit are backward |
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lead guitarist
intern
Joined: 03 Apr 2007
Posts: 123
Location: Texas
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| Posted: Fri Oct 24, 2014 10:35 am Post subject: |
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Not sure how the charge wires could be backwards? Here is the thing! Without a grid it prints, with one it will not! So that says short of some kind right? I am not 100% convinced it's a charge unit to drum distance issue as that is fixed and I see no wear or scrapes on the drum at all. Kip says that there is an issue with the grid, but not what that issue is! Not a lot of help really!
Lead Guitarist
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If it's too LOUD get some plugs!! |
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Placebo
intern
Joined: 06 Dec 2012
Posts: 139
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| Posted: Fri Oct 24, 2014 11:03 am Post subject: |
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It definitely sounds like a short to ground kind of issue. Could it be the orientation of the grid plate? Backwards or upside down?
You mentioned that there was about a 1/4" gap keeping the process unit from seating all the way in. Did you already resolve that? If not could there be an obstruction on the end of the drum that mates with the cross pin? |
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tech2tech
doctor
Joined: 04 Mar 2005
Posts: 377
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| Posted: Tue Oct 28, 2014 5:36 pm Post subject: |
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I had a grid screen on a 8000 that worked but was looking bad so I cleaned it with a scotch brite pad and had it looking brand new. As soon as I put it back in the machine I had the exact same issues you are talking about and had to replace the grid screen. My guess is there is a clear coating on the screen but that is only my guess.
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"If you mess with a thing long enough, It'll break" |
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lead guitarist
intern
Joined: 03 Apr 2007
Posts: 123
Location: Texas
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| Posted: Thu Nov 06, 2014 2:29 pm Post subject: |
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THE FIX WAS...... Removing the tab that is on the L.E.D. head and contacts the Charge unit! The return path for Grid voltage Why this is no one knows. The guy from Kip and I spent an additional 8 hours on this, bringing the combined total hours to diagnose and repair to a whopping 52 hours!!
Heck if taking parts OUT of a machine to make it run is going to be the norm? Then we are in for some fun!
I hope this helps someone in the future. Think outside the freaking BOX!!
Lead Guitarist
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If it's too LOUD get some plugs!! |
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