Riso RP3790 coverage issues

[Guest]

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Hey everyone,

New to the thread. I work for a church and we recently purchased a secondhand Riso RP 3790. Looks like the machine has been taken care of very well and all moving parts seem to be working but the thing I've been having trouble with is the copy coverage, or quality. When I create a new master it takes at least 40 prints before the copies look semi decent. Everything comes out like there's not enough ink in it. I have 6 drums and every drum that I've tried so far has given me the same results. Also the ink doesn't seem to be drying. I let it dry for a few days sometimes and it still seems to smear when I pick up a stack of sheets on on my fingers. This smearing is even happening on copies that aren't getting the correct density. I have no clue about anything on this machine besides how to load it, how to empty the trash bin, and how to make a master. I found some information in the manual on "Inking the drum" and I tried this several times but it didn't help at all. Let me know what anyone thinks. The people we bought it from said it sat for 6-8 months, they thought maybe the ink was too old but I pulled the black ink tube out and looked and the date said 13/10 which I'm guessing is October of 2013. If that's correct I don't think this problem should be happening. Also its consistently bad with every color that I've tried. I'm going on 500 copies with the blue and still with every new master the first 30 copies are un-useable the rest I can make do with. I attached pictures of the prints I've tried to make. The one with barely any ink on it was the first copy from new master. The other picture was the 70th copy that It printed. It looks good in the picture but if you zoom in on the bolded text at the top you can see the ink is splotchy and not covering well still. And the clipart should be bolder

Thanks in advance for the replies!

[mrriso]

Re: Riso RP3790 coverage issues

If the machine has set that long, the drum screens could need to be replaced. Check if the ink is Genuine Riso ink. If it is not, get some Genuine ink and run at least 1000 prints per drum to get rid of the old ink. You should also check the pressure roller. It is the big black rubber roller in the machine under the drum. Loosen the big screw holding the bearing in place to remove. Scrape the roller with a steel ruler to remove the excess ink/paper dust build up. DO NOT USE ANY CLEANERS TO CLEAN ROLLER. If the roller is soft it needs to be replaced. The inks do dry slowly, blue being the slowest. But they should be dry within 24 hours. Good Luck!

[taylorjones_11]

Re: Riso RP3790 coverage issues

Okay I checked all that out. The ink is genuine riso Ink. The roller If it is where you described looks perfect. I didn't even pull it from the machine because it looks so clean. You said something about the screens in the drums needing to be replaced possibly? how would I know, also would that happen just from 6-8 months of sitting? Every drum that I've tried has given me the same Identical results too. I pulled out the black ink tube to make sure that the consistency of the ink looked good still and without a better way of describing it looked like a hersheys kiss on the end of the tube where the outlet was and there didn't seem to be any air pockets in the tube. Keep in mind, I have very little experience with these machines I want to learn and figure this problem out though.

[mrriso]

Re: Riso RP3790 coverage issues

The screens can clog after 6 months of non-use. They are supposed to last 1,000,000 prints, but if stored incorrectly can clog sooner. My suggestion is to run a thousand of copies on a master then make a new master and run a thousand more. Do this for each drum and see if it helps. If not you may need new drum screens. FYI the first 5 prints on a Riso are usually light but after that should be OK.

[Iowatech]

Re: Riso RP3790 coverage issues

If you don't use the machine that often and this is what happens, it kind of sounds like automatic idling is turned off.
Somewhere on the left hand side of the control panel there is an "Idling" button. Try pressing that and then make your master. The machine will run for a while before it actually makes the master, but don't worry, that's what is supposed to happen.
That's the manual way to perform the idling process. Kind of a good thing to do if the drums have been idle for a while.
Depending on how long the drums have been idle, you will still get some prints with light coverage.
But if that works, it will be way less than forty.
Also, if I understand correctly, this is a problem on all the drums equally. If that's the case you might try resetting the machine's working memory by holding down the "Reset" button while turning the machine on, and continuing to hold the key down until the display shows that the machine is ready.

[taylorjones_11]

Re: Riso RP3790 coverage issues

Alrighty so I tried what Iowatech said and it seems to have worked for a couple of drums. My green and teal work phenomenally now. Perfect coverage on the second page that comes out of the printer. I was pretty blown away whenever I saw how the coverage was with those colors. I was having problem with the red. Not sure if I was supposed to do this but I pulled out the ink cartridge and noticed that the ink in the end of the tube was pretty gummy so I squeezed it and the gummy part fell out. I noticed my coverage improved dramatically after I stuck it back in there. So now I'm trying it with the black. Problem I ran into with the black is that a lot of ink fell out of the tube when I squeezed it so the riso thought the cartridge was empty. I just got done re-inking the drum and now trying a new print... seems now to be printing out with great coverage, and cleared up after just a couple of prints instead of 100. If I'm doing something detrimental to the machine then let me know but I'm happy that its working now. My guess is that ink gummed up in the outlet of all the tubes and pushing out the old and having the drums suck in the new has fixed the problem