GR3770 image position on master

[sscottsr]

I have a Riso GR3770 that I have had for years. Suddenly it has started doing something that I have never had happen before and I am hoping some of you guys can help.

The position of the image on the printed sheet is all over the place from master to master. It is not a paper feed problem as is so common, but is actually the image position on the master. I am not using the scanning platen, but printing through an SC7700. I can send the same page to the Riso three times and have three different positions on the master. For example, the first image may be almost dead on, but then the second image might be nearly 1/4 inch forward on the master. Then, without changing anything, I can make a third master and the image might be 1/8 to 1/4 inch behind. Again, it is not just how the image hits the paper as would be from paper feed issues, but the image is "imaged" on the master at different places—sometimes so far off that you can't even re-center the image on the paper using the print position adjustments. It might make three or four images on the masters in the same place and then who knows.

At first I thought there could be a drum issue, so I swapped drums. The problem is still the same. Then I thought perhaps the masters weren't feeding right so I cleaned the rollers and even tried a different roll of master material, but the masters always load precisely—it is just the image is a different place. I thought the drum might not be centering each time, so I started manually checking the drum between masters to make sure it was centered. I have even checked the timing just to make sure. Everything seems in order, but the problem persists.

Any help or suggestions would be appreciated.

Thanks,
Scott

[jermyth]

Something might be up with either the SC7700 or the image procssing PCB. See if happens with scanned images, if it does then its something in the machine (image PCB?) or not then something with the SC7700 or even software related.

Good Luck.

[sscottsr]

I should have thought to try scanning before, but it doesn't help anyway. I made a master and then without touching anything made another master. The second was "behind" the first by nearly 3/8 of an inch. So it appears that it is not software or SC7700 related. Any other ideas? Thanks.

[jermyth]

Check the write motor, the pulleys and the belt that drives the write roller. Also disconnect and reseat ALL the connectors on the Image Processing PCB & the TPH Power PCB.

[mikadonovan]

On the end of the write roller is a belt driven pulley. Remove the belt and tighten the allen screw holding it to the shaft.