CD74 Feeder issues

im having a problem w the feeder on my 5 color CD74. When watching the pickup suckers while the feeder is engaged only one sucker assembly is fully extending. The other barely moves in its anticipated up and down motion. The paper will still feed w some adjustments but the issue its causing is tearing the tail edge of the sheet due to its unbalanced pickup

 

Unless the sucker bodies are so old that the oil free bushings are shot (grab sucker piston and check for excessive play) the problem really would have to be a blockage or crack in the vacuum line. My guess, it's a hole or crack in the line. Worst case, a bad stage in the compressor.

 

Sucker bodies seem ok not a lot of dirt or deposits there no play Ive replaced the rotary valve no change there. Havent been able to find any leaks guess ill have to maybe dig further in that direction. That should be fun lol. Thanks for your reply much appreciated!

 

Have you checked the internal hoses in the air cabinet? I'm not sure what your CD74 is running for feeder vacuum, but I'm going to guess it's the Busch at the bottom tier. Maybe check manually the vacuum port.

 

As long as nothing is bent, usually the silver bullet here is to just spray a small amount of WD-40 on the sucker shaft. It can work miracles.

 

WD40 can cause gumming, factory recommendation is powder graphite.

 

Im betting the sucker assemblies are worn. You can try switching the suckers from one side to the other and see if the problem follows the sucker, or the installed location???