I dont know anything about the Technics SL PG300, but I know that most of the CD players that I have run across have a tiny hole in the front that you can insert a paper clip or piece of wire into...CAREFULLY mind you, but if done correctly will pop open your CD player...perhaps there is something lodged in there...
Anyway, if it does not have it, I have no more advice...but I was just thinking that it may have that feature in it.
I have a Technics SL PG300 single disc CD player and the CD drawer will not open. I can press the eject button it will open only about 1/4 inch and after a few seconds it closes completely by itself. I have a CD in it and it plays fine but I can't eject it. I want to remove this CD. Any help is greatly appreciated.