Replacing 12AU7 tubes in a Prima Luna Dialogue integrated amp

Bought the until about 2-3 years ago, as the core of a new system (Dynaudio Excite 34X speakers, Rega 8 w/ Apheta 2 cartridge, Rega Aria phono amp, Oppo BDP-105D for CDs plus video).

Very happy with the system.

One of the 12AU7's crapped out, so buying a new set.  Tried pulling out the bad one, and its really, really tight in the socket.  Never swapped these out before, not sure if the just pull up, or have some cam lock to hold them in. Afraid to force it, possibly break something on the socket, it sure seems very very snug.

Sound normal?  Just keep pulling up until it moves, or ? 

Any tips, tricks or info appreciated.  (and yes, I am using the gloves PL provided for all handling of amp items.)

Richard