GR 3750 color drum prints to the edge of paper

**farabundo** · 08-10-2016

Hello,

One of my GR drums (red) prints to the edge of the paper, causing a good portion of the print to appear as if it was full bleed. I'm guessing this is a problem with registration, although it has confused me that this only occurs with one particular drum. I was planning to do a maintenance/overall cleaning of my GR 3750, including having a look at the P disc, could this be where the problem originates? I somehow think it isn't, as other color drums don't suffer from this problem, so I'm a bit clueless. In case it is, does anyone have a photo handy of how the P disc should look in the correct position? I've found one, pictured below, but am not entirely sure.

Any help is appreciated.

timing_adjustment.jpg

**farabundo** · 08-17-2016

Originally Posted by farabundo

Hello,

One of my GR drums (red) prints to the edge of the paper, causing a good portion of the print to appear as if it was full bleed. I'm guessing this is a problem with registration, although it has confused me that this only occurs with one particular drum. I was planning to do a maintenance/overall cleaning of my GR 3750, including having a look at the P disc, could this be where the problem originates? I somehow think it isn't, as other color drums don't suffer from this problem, so I'm a bit clueless. In case it is, does anyone have a photo handy of how the P disc should look in the correct position? I've found one, pictured below, but am not entirely sure.

Any help is appreciated.

timing_adjustment.jpg

Any ideas?

**allan** · 08-17-2016

If your other drums are ok i would not make adjustments on the machine.

**farabundo** · 08-17-2016

Originally Posted by allan

If your other drums are ok i would not make adjustments on the machine.

I agree. Any ideas as to what could be wrong with the drum that would cause this?

**Iowatech** · 08-18-2016

Originally Posted by farabundo

Hello,

One of my GR drums (red) prints to the edge of the paper, causing a good portion of the print to appear as if it was full bleed. I'm guessing this is a problem with registration, although it has confused me that this only occurs with one particular drum. I was planning to do a maintenance/overall cleaning of my GR 3750, including having a look at the P disc, could this be where the problem originates? I somehow think it isn't, as other color drums don't suffer from this problem, so I'm a bit clueless. In case it is, does anyone have a photo handy of how the P disc should look in the correct position? I've found one, pictured below, but am not entirely sure.

Any help is appreciated.

timing_adjustment.jpg

Can you share a picture of the print defect? Sorry, can't see what your machine is doing or the output you find irritating. That's kind of important because the P disk has little to do with what you've described so far. (Heh, if the P disk was the issue, you'd have problems with every drum you possess.)

**farabundo** · 08-18-2016

Originally Posted by Iowatech

Can you share a picture of the print defect? Sorry, can't see what your machine is doing or the output you find irritating. That's kind of important because the P disk has little to do with what you've described so far. (Heh, if the P disk was the issue, you'd have problems with every drum you possess.)

I sort of figured that, but also wanted to sneak in an opportunity to get someone to confirm whether or not the configuration in that photo is correct, as I want to do some maintenance to my Riso in the hope of it lasting a long time. It's not a great picture, but I've attached a photo of what prints using the red drum come out like, which is a full bleed on one side (literally printing off the edge):

image1.jpg

**20gaugeO/U** · 08-18-2016

GR's are 20+ years old, you are one component away from not being able to fix it cause the parts aren't out there any more.

If this one drum is printing off the page I'd think it's the drive chuck on the drum is loose (stick a large straight edge screwdriver in the opening and see if it moves left and right- it shouldn't, should be locked down). Where the large pin in the back wall of the machine meshes with the drum. 2 allen screws under the drum shell. Or the drum isn't spinning internally would be another lesser option.

**farabundo** · 08-18-2016

Originally Posted by 20gaugeO/U

GR's are 20+ years old, you are one component away from not being able to fix it cause the parts aren't out there any more.

If this one drum is printing off the page I'd think it's the drive chuck on the drum is loose (stick a large straight edge screwdriver in the opening and see if it moves left and right- it shouldn't, should be locked down). Where the large pin in the back wall of the machine meshes with the drum. 2 allen screws under the drum shell. Or the drum isn't spinning internally would be another lesser option.

I'm constantly worried about exactly that. I can't afford a newer model though. I'll check what you mention.

**Iowatech** · 08-19-2016

Originally Posted by farabundo

I sort of figured that, but also wanted to sneak in an opportunity to get someone to confirm whether or not the configuration in that photo is correct, as I want to do some maintenance to my Riso in the hope of it lasting a long time. It's not a great picture, but I've attached a photo of what prints using the red drum come out like, which is a full bleed on one side (literally printing off the edge):

Thanks for the pictures. I took a look at the disks in your first picture, they are exactly where they need to be.
I agree with 20gaugeO/U, the drive coupling on that drum is likely worn out (I used to carry a drum drive coupling as car stock for high mileage GRs before they were obsolete). If you must use that red drum further you will need to adjust the size of the original to compensate.
Or, just use a different color drum that still works. You won't have red, but you won't have that image defect either.

**farabundo** · 11-11-2016

Originally Posted by Iowatech

Thanks for the pictures. I took a look at the disks in your first picture, they are exactly where they need to be.
I agree with 20gaugeO/U, the drive coupling on that drum is likely worn out (I used to carry a drum drive coupling as car stock for high mileage GRs before they were obsolete). If you must use that red drum further you will need to adjust the size of the original to compensate.
Or, just use a different color drum that still works. You won't have red, but you won't have that image defect either.

Sorry for resurrecting this, but I never found the part you both mention. Is this the drum chuck/coupling you mention in the photo? How can I check if something is off (the reason why prints are going full bleed off the edge of the page)?

IMG_5876.JPG