Those four valve top action Jupiter euphoniums with too many parts that come unscrewed...

[bloke]

(These are the ones that are somewhat similar to a Yamaha 321.)
Once all those take apart braces get loose, probably within a week the young scholar is going to bust about four or five solder joints - with the horn all wiggly, and then it's toast.
It's 11:00 p.m., and I just came back in from spending a little under two hours reconstructing one of those. It's not particularly gratifying. It's all back together, everything is lined up, everything is unsmashed, and everything works. I didn't clean anything, I didn't burn much lacquer at all, I stuck on some missing felts and a pearl. I played a few sounds on it to make sure there weren't any leaks and that everything was put together correctly.

Under two hours - I'm thinking, was faster than I expected I would be able to do all that crap. I'm glad to be laying in the bed and posting this, instead of still out there toiling with that...thing.

... the one wonderful thing about this:
not one trip into the buffing room

bloke "offering a bit more reality to those who think it would be just amazing to enter into the instrument repair industry, and become a 'tech' "