2 Colour GTO 52 perfector misfeed detector tripping

We have an older 2 colour GTO 52 (conventionallly dampened). The air controlled perfector misfeed detector keeps tripping out, even though the paper is feeding just fine. It's not been used for a long time, so that little airbox might just need a cleaning, OR, it may need adjusting so it's less sensitive. Does anyone know how to adjust that little airbox? (Operator side, between the units, behind that snap on cover)

 

ok, first things first. lets confirm that it is in fact the box on the operator side. cover the middle two sucker feet on the storage drum, also make sure that any unneeded sucker feet are turned off for the sheet size you are running. if it still detects a missed sheet, go to the box and see if the pin is being pushed out against the switch during paper run. It should come out and stay out with slight movement during paper run. If you see the pin go all the way back into the box each time a sheet goes by than you have an air leak somewhere between the sucker feet and the box. check all the vacuum lines going to and from the turning valve. On a machine your age it is not uncommon to see the turning valve bad. 4-6 hours to replace the turning valve and all hoses.

 

Thanks. That's a huge help. I'm starting to get an idea of how the system works. Next time we've got some time, we'll get it working, or figure out why it's not, at least. Trouble is, we use that perfector rarely. Last time it worked, with a lot of hiccups, this time it didn't at all.