I'm just hoping to be able to see if the laser is actually working.

This is on one of the old Sony 400 disc mega changers that I'm trying to save.

As it is now it will power up, load a disc, but then "disc is dirty" or "cannot read disc" comes up in the display.

I recently added new drive belts as the old ones were an issue but don't want to buy a new laser assembly if the one in it is still good, as that is like a government project where they keep throwing money at it and hope it works...