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Ever since I got my PT20p about a year ago, I have had this slight rattling noise coming from the horn when I play. I think it is a spring(s) but I'm not sure. It's never been an issue until this week. I don't know what changed but now I can't play because the rattling is louder than my notes... I asked one of my old tuba teachers and he said that he has had a similar soft rattling sound with his piston F but it has never been an issue. He did say he knew it came from his first piston spring though. Problem is, I can't tell for sure where the rattling, buzzy noise is coming from on my horn! I've tried readjusting the springs, tightening caps, looking for something inside the horn, and looking for a loose solder but I can't find anything and it seems like the rattling is getting worse.

Has anyone else experienced this problem and/or know how to fix it?

Remove the springs, put the pistons back in, tilt the horn forward, play. Still rattles, then maybe a solder failed.

Loose lyre screw? How about a blob of solder INSIDE the piston rattling around? Was the horn new when you bought it? Could the stem have been broken off and the threaded part is INSIDE the piston?

I had something similar recently on my MW 2250 - it drove me nuts (ok, more nuts actually) trying to find it. I thought it was probably springs so I tried everything with them, and it turned out to be the pearl insert in the 4th valve cap. It certainly didn't feel loose, there were no hints until just before it actually fell off. A bit of gel superglue and no more rattle.

bloke wrote:loose filling...??

old hearing aid battery...??

ROFLMAO

I agree with TheHat Tuba, remove one spring at a time, then play your horn while holding that valve up.
Repeat with the other springs until you find which one is causing the problem or you decide it had nothing
to do with the valve springs

An exotic possibility, but I seem to remember an old thread about a tuba with a loose rim-wire that rattled.

Also worth checking are water-key screws and springs.

And soldering on the stays - it's rare, but if there is torque on the stay, the solder can give way, resulting in only a light contact between the stay and the tube it should be soldered to - perfect for creating a rattle/buzz.

On older horns with metal valve guides, they'll wear down. When you engage the valves there will be some wiggle room between the valve guide and the groove on the inside of the casing, causing a rattling or clanking sound when playing. Check with your repair shop and see if they can do a nylon valve guide modification.

Your horn has 4 pistons and 1 rotor, correct?
If so, oil the rotor. They sometimes will rattle or buzz if they get dry, particularly when not engaged. Had that happen on my CB50. Only found it after a friend told me of his horn doing the same thing. A little oil and annoying buzzy rattle gone.
Bill

Play it with someone standing nearby. Have them listen carefully to all points on the tuba. Many times it's the spring, but it can be a loose solder joint. Once I had a buzz and went crazy looking for it. Turns out, there was a BUTTON in the bottom of the tuba. Apparently, it popped off one of my tux shirts. DOH!!!