On many of the PS2-related message boards I’ve looked at, there is an ongoing debate (well, it’s more stated as accepted fact) that using low quality DVD-Rs will damage the laser in a PS2. Now I’m not talking about reliability of the discs, or problems with the longevity of the discs themselves (this I accept as true).
However, can anyone confirm or deny this claim? The rule of thumb that I’ve heard is that the darker (dye) the underside of the media, the better it is (for your laser). Apparently the claim is that cheap disks make your laser work harder and thus wear it out faster. Sounds bogus to me.
Here’s an example of one such claim. Here’s another.
If that means light bulbs will wear out faster in a darker room, maybe (well, the analogy is the same, both are wrong).
As for the media question, what’s likely at issue is the tolerances of the center hole and anything that would affect the balance of the disk. The screeching sound that is referred to in one of the posts (if it’s not b.s.) is probably the bearing from the spindle. If that bearing goes bad, the spindle drive motor will die and the ** CD ROM drive ** will die. The laser is a static device, it’s on or off, it doesn’t adjust to any variable conditions. So: laser dies; bogus, drive dies; quite possible.
Some CDRs are more reflective than others and nearly all CDRs are less reflective than pressed media (this is why some older drives simply cannot read recordable media).
If the drive has a coping mechanism whereby the laser output is increased to compensate (and I can’t say I’ve heard of any such thing), then it could damage the emitter, but only if the design has allowed to coping mechanism to drive the laser beyond its specifications.
But that coping mechanism would work to the contrary of the original claim, which stated that darker media was better for the laser.
Personally, I think the whole thing is bunk. I can buy the “cheap media being poorly balanced” story, but not some direct effect on the laser. I thought the Pergo analogy was spot on.
Ooh, I didn’t notice that detail; you’re right - even if the disc was too reflective (and by ‘laser’, the person making the claim actually meant the entire opto apparatus), it seems highly unlikely that an increase in the reflected light would damage anything (if it was likely, the disc would be simply unreadable and damage would occur afterwards…
Thanks for the input, all. Sounds like you agree with me that it’s bunk. My guess is that people’s PSs just crapped out on them (as all electronics do from time to time), but they happened to be using cheap media at the time and thus the legend was started. Kinda like how everytime my friend uses cheap petrol, his car gets a flat tire. Although I suppose for the analogy to truly be apt, the gas would have to touch the wheels.
Still, to be perfectly honest, I’d sleep a lot better at night hearing Q.E.D. weigh in on this.
The out-of-balance issue is certainly significant. As for the laser itself:
During spin up, the lens “seeks” up and down (as well as back and forth), if the electronics get suitably confused, the lens will bang into the disc. This Is Not Good. The more it happens, the more likely it will happen in the future. Eventually, the lens won’t focus etc. (The laser is completely unharmed by this banging.)
There is no question that cheap media and cheap drives together make this occur more often.
(It’s also possible for things to get really screwed up and the disc spins too fast or too slow and then things start heading south. Not so likely on newer computer drives.)
In short, if you hear that knocking sound, or other strange noises, take out the disc right away. See if it’s the disc or the drive, etc.
Even if 100% of the laser radiation were reflected back into the diode laser, it would not cause and damage. The lasers used in a PS-2 are the same as those used In DVD players. It is a red class IIIa laser (between 630-650 nm), which means it’s ouput power cannot exceed 5 mW. This isn’t enough to cause significant heating, beyond the heating incurred through natural losses in the diode element.
I second the other theories posed here regarding cheap CDs. It’s more likely a mechanical failure mode.
The following applies to laser pickup technology for audio CD and laserdisc drives manufactured on the 90’s. I worked in the service industry repairing these drives at component level, also doing the fine-tuning on the optics when they came in for service. I also worked closely with Sony’s field engineers to identify design defects and issue service bulletins. Although I have not examined the laser pickups for game systems, the drives look virtually identical from the outside and I can’t see any reason why the basic drive technology would have changed in a few short years.
There now that that’s out of the way…
The light output from a semiconductor laser is precisely controled by a feedback loop. The optimum laser power is pre-set by the OEM. As lasers begin to wear out, and their output begins to fade, this is detected by the pickup device and a correction is made to the drive circuitry to increase the current through the laser diode. This works well up to a point. After a while, the laser gets weaker and increasing the current through it only pushes it toward the repair bench faster.
If the disc surface were too reflective, an opposite correction would be made and the laser would receive less drive current and subsequently have lower output ligth levels. So you can not burn out a laser by reflecting its own light back at it; that’s how they are supposed to work in the first place.
However, there is a sliver of truth in the OP. The optical drive also contains coils that can finely position the laser’s objective lens on the Z and X axis:
If the disc is warped so that the distance between the data surface and the lense constantly fluctuates as the disc spins, the Z axis drive coil (focus coil) will work overtime trying to constantly keep the lens at a certain fixed distance from the disc.
The spiral data stream on the disc is supposed to be as concentric as possible with respect to the center hole. If the data spiral is slightly eccentric, the X axis coil (tracking coil) has to become energized to keep the lens properly fixed on the data stream as it wobbles around while the disc rotates. The more eccentric it is, the harder the tracking circuitry has to work to keep the laser’s beamspot on track.
Either of these can wear out the circuitry that drives the coils, or wear out the coils themselves. However I doubt that this would cause a serious run of defective units. At absolute worst, it might cause a slightly reduced lifespan of the player. It certainly wouldn’t cause boatloads of players to suddenly fail.
But the main question of the OP (that disc reflectivity can damage lasers) I find to be a virtual impossibility. In fact…
The opposite has a better chance of being possible. If the disc isn’t reflective enough, there won’t be enough light reflected back, and the laser power will be bumped up by the feedback circuit. Burning the candle twice as bright, so to speak.
Consider, too, that over the lifetime of a drive (even if it is shortened) you would likely spend more on better media than the replacement cost of a drive. Replacement might even be better in the long run, because next year’s higher performance and capabilities will cost less than this year’s model (if the evolution of the closely related CDROM drive is any indication)
Sometimes you want better media (e.g. for long term archiving), but in those cases, cheap media shouldn’t be considered at all.
