Hello, I have a National 500B with a 3 section boom, 56 foot stick. Nice boom truck for it's age. Been working like a champ but I am having a few issues. I greased the boom as there was some squeal when boom was extended to the full extent. Cleaned out the bird nests on the inspection hole in the main etc. We had the boom fully extended near the ground, but the main boom cylinder wouldn't retract all the way. I assumed we were reaching the limit on the extension with the man basket attached. Still has some squeal at extension max but seems better overall. Raised the boom to retract the extensions when I was putting it away. Problem is that the winch goes down real slowly, raises up fast though. Other issue is the boom will no longer go down. Raises up ok, but nothing on the control when going down. All other hydraulics seem ok. I checked the safety relief valve on the bottom of the control panel and it seems ok, pushes in like it should. Any ideas out there? thanks much
Whenever booms get greased for some the top pads rarely get grease. At the top, rear of each boom sections the pads rarely if ever see grease and it seems like a squeaky boom is usually related to that. I would check linkage for the cable down. Follow linkage from the control lever to the valve and make sure the valve is moving all the way in both directions. That could be your boom issue too. The other thing that would stop your boom down would be the a2b/overload cut out. I dk how it's set up on a national or it yours even has it but that's were I'd start.
Thanks for your ideas. I will check it and and let you know.