I think my hot water cylinder outlet is scaled up

Hi everyone: I think the top connection to my hot water cylinder is scaled up or blocked... the hot water only comes out with a dribble (and intermittenetly too at times). The shower is fine (fed from a flange at the side lower down) ... all the other hot water draw offs are blocked. Can I prove or make 100% sure of this before draining down the cylinder a little bit, and disconnecting the pipe, and cutting out and replacing if necessary? Will the magnet trick detect scale like it does sludge?

Thanks for helping

magnet will not work , but it is very common cylinder blocking on outlet . All depends how tight pipe is you maybe able to spring it out the way once nut undone

Could simply be that there is an airlock on the top outlet.