Why wont my 250gb PS3 slim play PS1 games?

Hi, just looking for a little help! I used to have a 120gb PS3 slim until that broke, now I have replaced it with a 250gb slim but it wont play PS1 games! I have created a virtual memory card for it, turned on the upscaling, but I just cant seem to get it to work..
Any help is much appreciated!