[charlie_ps2]

PJClark and Arakon come closest to answering the point which has now focussed on laser damage. So here's the full skinny.

The Laser means the Laser Diode, the semiconductor that lases to produce coherent light. This diode is a sandgrain in size reaching 70 deg Centigrade. A very small increase in current (like pushed through by 5v or by over-reducing the resistance using the recalibration pots) will take the temperature through the breakdown barrier so that it lases dark light or weakly lases at the right wavelength. So yes, like a light bulb, the Laser will eventually wear out according to use.

A cheapish DVD-R has about/less than half the reflectivity of a pressed DVD and the laser power required to avoid re-reads is higher on poor media, achieved by re-calibration. A more expensive DVD-R (e.g. Verbatim) has about 60% ideal reflectivity which, with a clean lens, is sufficient to work with the standard laser power, esp. on a v5.

So now we come to the CD/DVD decision. Gamegizmo is talking bollocks - the TOC is irrelevant and relates only to the used portion. You can have less than 650MB on a DVD; what would the PS2 think then? When the disk is inserted, you can here something akin to a mouse squeeking very rapidly. That's the lens moving up and down to focus and side-to-side to locate the groove that it follows to obtain the data. This lens movement is activated by magneto through tiny wires, current and magnets. Then the sled traverses the disk to measure its diameter (there are mini sized CDs).

When focusing, it tries first in red light; if there is reflectivity, the disk is a DVD/DVD-R and it can boot; if it is not a PS2 disk, the red screen appears.

If there is no reflectivity, it tries infra-red light and if there is then reflectivity, the disk is a CD/CD-R. if it is not a PS2 disk, the red screen appears.

If there is still no reflectivity, it goes to the broiwser. Either the lens is dirty or the laser cannot muster enough power and needs recalibration and eventual replacement.

There is an outside chance that the laser needs adjusting for the lens being parallel to the disk (azimuth) or the sled being parallel )the white cog).

So, who's up for a challenge on this lot?