Pull the tubes in an "upward/vertical" motion. Try to hold it as far down from the base as possible if you can. A soft cloth rug can help you hold the tube more solidly. If it seems that the sockets does not want to let go, use a few drops/spray of Progold and the like to "loosen" the pins friction from contact to the socket and with a pulling motion, rock it gently but not excessively.
I have never seen a tube socket with a release lever. Maybe somebody can answer you on that.
I have never seen a tube socket with a release lever. Maybe somebody can answer you on that.