How to open this rotary valve clock spring barrel?

[Bhrzg]

Hi all,

I started my tuba journey about 1,5 years ago by buying an old Amati for 150 euros. It's been great fun learning to play, but now I have a problem: the clock spring of the fourth valve broke.

I have disassembled the lever assembly and separated the problem lever/spring barrel from the shaft. But how do I continue from here, how do I get the barrel open? I don't see any other way than to use a suitable sized piece of rod or wooden dowel to push the center piece (the one with a star shaped hole at one end and round hole at the other) to force one of the barrel lids open. But which side should I try to open? And should I try to hammer it or use some kind of vise to push?
Also, should I try heating the barrel and cooling the lid to help loosen the joint?

Any other advice or suggestions?

Thank you in advance!

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[bloke]

The sides are friction fit.

[bloke]

If everything seems clicky and worn, maybe look into a decent quality set of Chinese exterior sprung linkage.
When when the links themselves are replaced with European links, the rest of that stuff is usually pretty good.