I have a N80CB1 that I have used very little through the years. I took it out of storage to do a small framing job and fired one nail and the gun started leaking air at the trigger. I purchased a new tva6 trigger valve (generic knockoff) and installed it and the gun acts exactly the same. I disassembled the old green valve and looked it over and see no bad orings on the old unit. Is it possible that this nailer has a different issue causing these symptoms or do I have two bad valves?

Thanks for the follow up. I had just taken the rest of the gun apart and inspected everything when I saw your reply. I had found nothing wrong with the rest of the gun, it all looks brand new. I decided to take the old green trigger valve apart again to see if I could find anything. I completely disassembled it and the uppermost piece that has two orings on it and is pressed up into the top had what appeared to be some kind of hard clear material trapped in it. Could have been a clear deteriorated oring. I then inspected the replacement valve and it appeared that the main trigger side oring was a smaller cord diameter. I swapped out that oring with the old one from the green trigger and it works! Wish I had found this site before I purchased that piece of junk on ebay! Thank you for your help.