some PS2 modchips require changing modes to boot PS1 games. The most common way is while the console is in standby, press and hold the reset button until its blue LED comes on.

 

Yeah, its basically instead of just tapping it as usual, you hold it a few seconds till the light is on. That's how it is on my Magic V and I know some varieties of the Matrix chips use the same method. If it doesn't work just google something like "chipped PS2 PS1 mode" and try the different methods.

 

The only way to change to PS1 mode with the chip I have, which I think is a Magic V or a clone of it is by holding the reset button, nothing with the controller at all. It is possible more expensive or later generation chips did it using the controller, however I've never heard of it. I never really looked into them again though after I got mine.

 

I have a similar problem myself. It used to work, but then a couple of months ago, the laser started to have problems playing discs (all discs, it would spin it up, and then stop it, and it would do this a couple of times while the laser tried to focus on the discs, never being able to), so I bought a new laser assembly from amazon. After installing it, discs run fine sometimes, but sometimes I have to disconnect the laser assembly and reconnect it to make it work (but I am not asking for help regarding this now; this thread is about PS1 games not running on the PS2). Anyway, after installing the new laser assembly, no PS1 games will play; neither legit ones, nor the backups I've made. Do you guys think that the laser assembly is faulty, or is it something else? I have a slim European SCPH-700xx, with a Matrix Infinity modchip installed. I just found out about the laser fix today, so I have not one installed.