I'm a backhoe newbie so I don't know what's inside the control tower. Last time I was working with the backhoe the dipper stick got stuck. It would come in, but the when pushing the lever forward past center it wouldn't go. It would just stop. I didn't force it. I was clearing branches above a roof, so the bucket was up high. I Swung the backhoe away from the roof before causing damage. After working with the lever a bit it came loose and all was good again. It felt like a linkage issue of some sort. Does this just happen sometimes, or is there something I need to fix? Thanks for any insight. I'm just learning this machine.
Very few lubricate these linkages. I briefly owned a three stick, foot swing 580K, then switched hoe & linkage from another 580K. In doing so, I gained joystick control, and an extend a hoe. Kept it 14 years, it is now owned by a friend. I'd start by removing the cowling and get in there with Aerokroil. Lubricate all pivot points. once everything is freed up, use 90 weight gear oil & a q tip to lube each pivot. A particular problem is the pivot mechanism for the foot pedals. The N series may have grease fittings to lube the pivot. Do NOT latch it in transport position trying to snap it up, reverse to latch. They have a rubber snubber in the boom to swing tower joint wears out fast. The strain will crack something. Some have a ductile iron boom, can't be welded. I have a 580 Super N. I only use the stabilizer to latch it. My son tried snap latching it, it was so violent he shattered a window at floor level front of the cab. He said: "I didn't mean to break the window." I countered: "NO, you meant to break the boom."
Two possibilities that I can think of, first being what Willie B just mentioned (stuck linkage, pivots), second being some contaminate in the hydraulic system jamming up the spool. Hopefully it isn't the latter, but it does happen, had to deal with that on my dozer a couple years ago. If it is something stuck in the spool don't force it, you'll ruin either the spool or valve body. You'll have to pull the spool out, flush that entire circuit, and blow some foam cleaning projectiles through it to get the debris out. Regardless, start by pulling the covers and look at the linkage. I've never messed with any of the N-series, but all the older ones had greasable pivots on each lever and two on each pedal. What you are experiencing with the stuck lever isn't normal and likely a result of poor maintenance in the past.
I second the something stuck in the spool theory. Maybe a good idea to strip the dipper cylinder & check it as well.....if something is floating around the circuit, the cylinder is the first place to look.