I was having a bunch clacking coming from the F-Attachment linkage on my YBL-822G. I looked down and could see some movement in the horizontal / rear part of the U-joint. I used a precision flathead to make sure it was tight, and it felt tight, but still was wobbling, so I decided to take it apart to see what was wrong.

I guess that was a mistake. When I was unscrewing what Yamaha calls the "Lever Connecting Screw" from the horizontal half, it was a bit difficult. I noticed there was some black oil, so I cleaned that off, and then figured it must have been dirty, and screwed it back in. That's when it went sideways, because it would not get tight. At all. I definitely did not use nearly enough force to strip out a screw, but that's exactly what it feels like.

I had unscrewed the vertical / front screw as well, and it now has the same issue. I looked at the Yamaha parts catalog, and I see listed "LEVER CONNECTION SCREW SPRING" for both the horizontal and vertical. I never saw any spring in there, so I'm guessing that's a mis-translation, or I have completely screwed things up. Is it supposed to be some type of "helicoil" type attachment where it never comes off?

AFAIK those are just screws. That first one does look a bit stripped out.

[quote="Burgerbob"]AFAIK those are just screws. That first one does look a bit stripped out.[/quote] I have the horn away now, but looking at the exploded diagrams,I'm fairly certain they are crush springs. Like a crush washer, but a spring, probably made from aluminum. I always wondered how those linkages never seemed to get loose or have any problems.

Tomorrow I'll see if I they are in fact crush springs.

Well, I found the part that is supposed to be in there, but I'm not sure this is correct, and I didn't see it in there anywhere.

This "spring" is used in the barrel connections of virtually every Yamaha trombone, so it's in both the "u-joint" as well as the 2nd valve levers.

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Took it down to Dillon Music today, and Fred fixed it. Turns out that the D5641280 LEVER CONNECTION SCREW(BS) YBL630G was the problem. It was stripped, so now things are back to normal with them being replaced. Still not sure how exactly the whole joint goes together with the "spring", which wraps around a post and gets kinda crushed to create a joint that doesn't loosen over time.