GR3770 Bad feed clutch?

[CenturyPrinting]

I've read these posts so many times I've nearly memorized them! My problem started when I bought a used GR3770 that's timing was really out! After getting the service manual and reading this forum, I've got it back into proper time, I think? It will sporadically feed fine, but sometimes will start "multi-feeding" paper until I get a jam error. It's as if the feed clutch is staying engaged because the feed wheels are turning when they should be stopped. If I hold back on the paper to keep it from entering the machine until it's supposed to, I can often get it to feed. Is this a feed clutch staying engaged? I have the older one with the brown wire, "thanks joelsa12 for pointing out how to tell".

I own a small but very busy commercial print shop. These Riso's are a dream come true for many applications. Besides the GR3770, I have a GR1700 that works like a dream and has paid for itself 1000x over! I recently acquired a GR2710 with a stuck drum in it, and a Gestetner 5930 that seems to work pretty good so far. Will the P/F clutch from the GR2710 work in the GR3770? I may use it as a parts machine if so, provided the feed clutch is the problem!

Thanks for this forum and all the valuable information!

[RRodgers]

Lower the tray height, that should fix it.

[CenturyPrinting]

Thanks RRodgers for the advice. If I understand correct, the tray height is the green dial to the left of the green dial for the angle adjustment, which I've read should always be at the 9 o’clock position, am I right or not? I've tried adjusting that with no success. I've thought it may be the tray height too, but the fact that the feed wheels are turning all the time makes me think its something else. Please let me know if this is the table height adjustment your referring to, or if there's something else I'm missing? On our AB Dick offset presses, the table height raising to quick or not quick enough will dramatically effect the feed. Those presses are suction feed rather than friction feed however.

Thanks.

[joelsa12]

yes the clutch is the same, and you could check and see if it was causing the problem with the feed. if it has a brown wire you can take it apart and clean it. dirt will build up on the inside of the clutch and it will cause it to stick and stream feed. if you swap the clutches and still have the issue you it could be the tray height like metioned above

[RRodgers]

No, with the dials you are dealing with angle and pressure of the sep pad. The height adjustment is the screw right above the pick up tire. (if I remember right I don't see to many Riso's anymore) I don't remember which way to turn it... just turn it so that when the tray comes up, it doesn't come up as high. Maybe drop it a mm or two. Too much upward pressure on the paper will make the machine just feed in a bunch at once.
GL

And just to clarify (and not to put you or anyone down) if it was the feed clutch it wouldn't make it off the tray in the first place. But I have seen prob's with the small feed clutches needed cleaning or replacement. Not like the clutches on the GR 3750 (once again if I remember right) those are the big monster clutches that I don't think I've ever had a problem with.

[joelsa12]

bad clutch = no feeding and dirty clutch = stream feeding. i have seen a dirty clutch cause stream feeding hundreds of times.

[CenturyPrinting]

PROBLEM SOLVED!

Thanks to everyone who helped in the effort to help me diagnose and fix this thing! You all are wonderful! And joelsa12, you’re a genius quite frankly; of course I already knew that from reading your other posts on this forum! You always seem to nail it right on the head! The feed clutch was indeed the problem. It was sticking and multi-feeding paper just as you said! I swapped the clutch from the GR2710 and the thing’s running like a dream! I’ve never seen it feed so well! As I’m writing this I’m listening to it click away on a 25,000 run, 8 ½” x 14” mail piece that will be tri-folded and tabbed tomorrow for mailing! It hasn’t missed a lick! It's true music to my ears! I've never got it to feed more than 500 sheets or so before the stream feeding would start after re-filling the tray! I'm up to nearly 20,000 now! The sheet to sheet registration even seems to be improved!

Now with the GR3770 in action, I can run those 11x17” pieces I need to, and card stock as well. The GR1700 has never liked to feed anything over text weights and sometimes 67# Bristol Vellum, but never 65# cover stock or above (Yes 65# cover is thicker than 67# Bristol Vellum!). However, it will feed carbonless paper without ever double sheeting which is difficult, as it’s the nature of NCR to want to stick together even without the glue! The GR3770 does all the other stuff great and it’s running like a champ! I can’t thank you all enough! I hope to be able to return the favor soon!

[joelsa12]

last thing would be I have seen those old style brown wire feed clutches that 3-5 million impressions before they are actually bad. if you pop the e ring off of it is will come apart. you can clean it with anything that will not leave a residue. and i would keep it as a back up just in case the other one would fail. just clean every piece in the clutch concentration on the part that the wire goes into. it will be the white area. you will see lots of build up in it if you take it apart.