Hi there,

a friend of mine and I have been working on a RISO MZ 790U that was shipped from California to Minnesota many years ago. Somewhere along the way we think it fell from some height (like off the back of a truck or something) and the fall damaged the unit in many ways. It sat around in various people's homes over the last couple years until it came to us... and we're determined to restore it!

Following the MZ/MV service manual, we've been able to fix almost all of the mechanical issues and we finally have the unit printing! ...but now we're struggling with getting the two drums that we have (Black and Magenta) to print evenly and consistently.

These drums have obviously sat around for awhile, so we tried cleaning them with denatured alcohol, running the idling action, and printing a couple hundred copies but still... couldn't get the images to come through. We tried to replace the screen on one of the drums (magenta) and we tried our best to make it as tight as possible using a spring-jig assembly very similar to the one in the manual. To our surprise, the images started to appear after replacing the screen ...but they didn't quite turn out how we expected. The images look kind of wrinkly, as if the screen is wrinkled, but we're pretty sure we made it realllllly tight... is it not tight enough? Anyone experienced this before?

The images still seem really faded and uneven too. Is there something more that needs to be done to get the images to print nicely? Do we need to take apart the drum and clean it inside?

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