RISO GR3750 Paper Jam Check Paper Feed Area Error

[filmplane]

I am getting a GR3750 up and running and trying to run some print tests but I can only run 1 copy at a time due to the "Paper Jam Check Paper Feed Area Error". I can do a reset to clear the error, print one copy and send a sheet of paper through.

The paper is not actually getting jammed - it seems like it is delayed as it gets picked up from the paper feed area. I have also checked and see no jams beyond of the single sheet print I am trying to run. Is this a timing issue? I am not getting any other errors - only the "Paper Jam Check Feed Area Error"

Also, there is hardly any ink on the drum - I gave it a good soak with de-solv-it citrus cleaner as the drum was pretty dried out.

If anyone can provide an approach to diagnosing this issue and resolving it would be greatly appreciated!

I have made two youtube videos showing the paper feed tray side and the paper receiving side to try to illustrate what happens when you try to print one copy. You will notice what I think sounds like a slipping/ skipping sound too:



I looked on the forum here and found these two posts about paper feed problems so wondering if it is some sort of timing issue as discussed here:
Paper Feed Problems (Risograph GR3750)

and here:
Riso GR 3750 Paper won't feed

[Iowatech]

Based on the second video, it could be that the wiring to the pressure solenoid is broken or the solenoid is out of adjustment. Or the pressure lever is worn to the point the solenoid can't connect to it. The machine could also be way out of time, too.
From the first video, it sounds a little bit like the guide roller assembly is worn out. If that is true, the machine is most likely done for. But let's assume that isn't the case for the moment.
It would be useful to see pictures of the back of the machine with the back cover off. It is easier for us to spot timing problems with them.

[filmplane]

Based on the second video, it could be that the wiring to the pressure solenoid is broken or the solenoid is out of adjustment. Or the pressure lever is worn to the point the solenoid can't connect to it. The machine could also be way out of time, too.
From the first video, it sounds a little bit like the guide roller assembly is worn out. If that is true, the machine is most likely done for. But let's assume that isn't the case for the moment.
It would be useful to see pictures of the back of the machine with the back cover off. It is easier for us to spot timing problems with them.

Ok, thanks so much for the preliminary diagnosis. Here is a video of the back of the GR3750 immediately after pressing the start button for one print and the Paper Jam Check Feed Area error occurs:


Here are two still images of the back of the GR3750:
IMG_0878.jpgIMG_0884.jpg

Thanks for the help!

[filmplane]

Hi Everyone, hoping I can get some assistance isolating the cause of this error. An Update:

Since I posted the previous images and video of the timing on the back of the machine, I adjusted the timing based on the RA Manual for the GR3750.
Here is a photo of the results of my adjustment: photo(1).jpg

In addition to adjusting the P-Disc and Pressure Sensor Disc, I noticed the elevator upper limit sensor was way off as well. I adjusted that also according to RA manual, too. I am still getting the Paper Jam Check Paper Feed area error. I have read other posts in this forum related to this paper jam error issue but have not yet had success on resolving the problem.

If anyone can help diagnose or point out next steps for possibly resolving this issue, it would be greatly appreciated! @Iowatech, thanks for the help thus far!

[Iowatech]

Sorry I didn't get back to you sooner.
First of all, undo the timing adjustment you just did, at least in respect to the right hand disk. The timing notch on that disk should be aligned with the lower corner of the sensor on GR3750s.
(Since you used a manual that in a lot of circumstances has the correct adjustment procedures I'm going to assume you adjusted the entire cam assembly and not just the right hand disk.)
The last video showed the pressure solenoid wasn't engaging, you might double check its wiring connections. You might also check its wiring with a meter to see if there is a broken wire, although it has the clear tube around it so that has kind of a low probability of being the problem.
Before I go any further, what is the total print count?

[filmplane]

Sorry I didn't get back to you sooner.
First of all, undo the timing adjustment you just did, at least in respect to the right hand disk. The timing notch on that disk should be aligned with the lower corner of the sensor on GR3750s.
(Since you used a manual that in a lot of circumstances has the correct adjustment procedures I'm going to assume you adjusted the entire cam assembly and not just the right hand disk.)
The last video showed the pressure solenoid wasn't engaging, you might double check its wiring connections. You might also check its wiring with a meter to see if there is a broken wire, although it has the clear tube around it so that has kind of a low probability of being the problem.
Before I go any further, what is the total print count?

Hi Iowatech, thanks for the response and no worries. I did not adjust the entire cam assembly. I only did a spot check that both disc holes were aligned with the cams. I stared at the System PCB and couldn't find that SW1 button to do cam adjustment and then just today stared some more before I finally found it. Should I try the cam adjustment?

I read the manual wrong and adjusted the right hand disk for "B4, A4, or Legal Models". I will readjust back to your suggested position (which is the one I should've done initially).

The copy count is 3038733 and master count 5380.

I will check the wires of the pressure solenoid. I noticed the pressure solenoid wasn't engaging, but I am new to the Riso so wasn't sure of the correct behavior. Thanks!

[filmplane]

More of an update from most recent post. I have readjusted the timing on the right hand disc to suggested position. Here is the latest pic: timing_adjustment.jpg

In addition on your recommendation about checking the wiring Iowatech, I checked the wiring around the pressure solenoid and did not see any visible wire damage. I have not checked wiring with a meter yet. I did notice that this harness is loose: pressure_solenoid.jpg

Would a test mode be helpful in identifying pressure solenoid issues? Not sure what next steps are...Thanks for all the help so far!

I also found this in the back recess of the machine (where the paper feed tray rests at lowest level. From a previous repair/ replacement? photo(4).JPG

[Iowatech]

First of all, to be totally honest, some bad news - this is starting to look like the guide roller assembly is worn out. That's why I asked about the print count. I used to carry the assembly to use for maintenance calls every million copies, and your machine's copy count makes it look like it is probably due.
For what it is worth, here's a couple of other things you might try if you want:
If you use test mode 68 and the pressure solenoid doesn't activate, you should consider that a sign to test the solenoid's wiring with a meter, and if the meter test doesn't show continuity it is a safe bet that one of the wires are broken inside the insulation. That's actually not that hard to fix, if that's the case I'll try to walk you through it.
One other thing, there are two kind of circular cutouts on the metal piece just behind the right hand disk and just below its sensor. I think if you look through the lower one you should see a hole in the cams that lines up with that. If not, you might want to check the vertical print adjustment.

[filmplane]

First of all, to be totally honest, some bad news - this is starting to look like the guide roller assembly is worn out. That's why I asked about the print count. I used to carry the assembly to use for maintenance calls every million copies, and your machine's copy count makes it look like it is probably due.
For what it is worth, here's a couple of other things you might try if you want:
If you use test mode 68 and the pressure solenoid doesn't activate, you should consider that a sign to test the solenoid's wiring with a meter, and if the meter test doesn't show continuity it is a safe bet that one of the wires are broken inside the insulation. That's actually not that hard to fix, if that's the case I'll try to walk you through it.
One other thing, there are two kind of circular cutouts on the metal piece just behind the right hand disk and just below its sensor. I think if you look through the lower one you should see a hole in the cams that lines up with that. If not, you might want to check the vertical print adjustment.

Thanks for the info Iowatech. The assembly you say that is most likely worn out - is this the part here: guide roller assy? I bought the entire GR3750 used for $100 bucks so if this is possible to repair I am game. If it's a goner, maybe this can be a parts machine for the next GR3750 I buy...

I went through a few test modes and here is what I found out below:
Test Mode 07 Pressure Detection Sensor - fast beeps, i.e. No Detection
Test Mode 68 Pressure Solenoid Motor Test:


Test Mode 114 Pressure Control Motor Sequential Op. Test:


Given that there is movement of the latch on test 68 - should I still test for continuity?
I don't have the Cam Adjuster jig but I did use an 8" screw driver only to test if the cams line up on the right hand side before I readjusted the timing. They are spot on. On the Pressure disc side (left side), I can also do the same with screw driver but it is slightly off but not by much. Not sure if that makes a difference or not but willing to try the cam adjustment on that side.

For what it's worth here is a Riso Service/ Parts log I found with the manual showing what has been done to the machine (at least up till 2002 - ha!): Riso Svc/ Parts Log PDF

Thanks again for all the insight!

[Iowatech]

Good news, I think the pressure solenoid just needs to be adjusted. The movement of the hook lever shows the pressure solenoid's wiring is good, but the hook lever needs to move further.
The RA manual should have the adjustment procedure, just follow the Position of Pressure Solenoid adjustment. The lower screw for the solenoid is the one that fixed the loose harness in place, so it is kind of important that gets put back together. Sorry I missed that earlier.
It wouldn't hurt to check the Resting Position of Hook Lever and the Resting Position of Pressure Lever adjustments too, but be careful with the pressure lever as there are some pretty strong springs attached to it.
That was a good idea using the screwdriver for an alignment jig. If I remember correctly, I think we used 3mm allen wrenches.
The guide roller assembly part number you found is the right one, but hopefully you won't need it for a while.
Sorry for not getting to this sooner.