Old 10-03-2005   #1
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Can a laser make contact and scratch a disc?

After about a year of great service and around 60 writes, my 2500 made it's first "Failed Burn" the other day. It appears that the surface got scratched by contact with the laser or something -- if that's possible. Here are the details:

It happened on a 4.7 GB DVD authored, rendered/compiled, then directly burned in Studio9+, using Fuji/TY -R 4x media from a batch that had always given error-free writes -- verified by Nero Speed. The stock 1.06 firmware is in place and always had allowed 8x write speeds with this 4x lot.

This time, however, the burn seemed to be taking longer than normal -- although I was distracted by work I was doing via a KVM switch on another PC at the same workstation -- so can't be sure. I switched back to the PC doing the write and saw that by the progress gauge, the burn should have been complete. But the writer's data activity light was still active.

I gave it a few more minutes to complete the burn but no progress was seemingly made -- so I aborted the burn by using the cancel button in Studio, and Studio promply crashed hard leaving an XP critical error message just before Windows crashed/rebooted on its own. But the drive activity light was off and I ejected the disc for inspection.

The burn area didn't go out as far as I thought it should have for a disc that only had three minutes of space left unused. My biggest concern, though, was the random scratches over the outer 50% of the disc, including the unwritten area. I usually inspect the surface of each disc before a burn to make sure it is free of dust, etc; I don't recall seeing anything abnormal on this disc before the burn -- but it was late, I was very tired -- so who knows? Perhaps this disc was damaged from the factory...

Fearing my drive was trashed, I tested it to see if it could still read; a pressed DVD played fine. Good!

Next, I tryed a 4.3 Gig data write to a +R disc, and that burned and read normally. Since then, I have done about 12 burns -- about 5 with discs from the same Fuji/TY -R lot that the failed burn was from -- with no problems at all. The only change I made was to limit my burn speeds to 4x, even though the FW allows 8x on these 4x discs, and I never had any problems with 8x writes before this.

So... what do you think happened? I have two theories:

1) The burn failed due to pre-existing damage on the disc; the drive is fine and did not damage the disc.

2) The disc was fine before the burn, but something corrupt in the software, the drive's hardware, or perhaps using a KVM switch during the write, caused the drive's laser (or other part) to contact the disc surface.

I had been concerned that perhaps the laser energy had somehow been over-driven and burned scratches on the surface... but that didn't sound logical. The surface is clear and non-reactive so the energy can reach the dye layer; an over-driven laser should have burned the dye layer and not the clear polycarbonate surface -- correct?

And burning a 4x disc at 8x on stock firmware, using media approved by the manufacturer and supported by the firmware's write stratagy -- won't cause the laser to damage the disc (via physical contact or high energy) -- correct?

I would be very appreciative for any feedback regarding a possible cause(s) of this strange behavior. I will not trust my drive to burn unattended until I solve this mystery. I have a scan I could submit of it if that would be helpful.

Sorry about the length of this. I did a search and couldn't find a relevant thread.

Last edited by RWP; 10-03-2005 at 18:17. Reason: Corrections/additions
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Old 10-03-2005   #2
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Re: Can a laser make contact and scratch a disc?

Sorry I did not read the complete post, but one question:
Do you look at the blank data side of the disc BEFORE burning, looking for scratches/dust/defects/etc?

My guess is if the laser unit or other unit is out of place, it will cause damage that pieces of plastic will fly while making ugly noise ...
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Old 10-03-2005   #3
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Re: Can a laser make contact and scratch a disc?

Quote:
Originally Posted by Goudo
Sorry I did not read the complete post, but one question:
Do you look at the blank data side of the disc BEFORE burning, looking for scratches/dust/defects/etc?
Yes. I'm very particular about clean discs.
Quote:
Originally Posted by Goudo
My guess is if the laser unit or other unit is out of place, it will cause damage that pieces of plastic will fly while making ugly noise ...
I didn't hear any unusual noise; I don't suspect pieces of plasic, etc, getting loose in there causing damage.
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Old 10-03-2005   #4
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Re: Can a laser make contact and scratch a disc?

Never monkey around with the PC during the burn process.
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Old 10-03-2005   #5
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Re: Can a laser make contact and scratch a disc?

I think it would be a good idea to blow in the drive to get rid of some dust in it. Then just try another 8x burn with the same project in Studio. I for myself believe that the disk had some damages before.
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Old 10-03-2005   #6
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Re: Can a laser make contact and scratch a disc?

Quote:
Originally Posted by furballi
Never monkey around with the PC during the burn process.
Hey, that comment is too severe. We're living in the age of multitasking though my mental damage from the "buffer underrun = death" drives wasn't yet fully cured.
At least KVM switching should be much, much safer than web exploring, I believe. (In fact, I do both very often.)

For those who don't have a good computer spec, it's not a good idea to give it a full load during burning. Especially massive use of hard drives can be the killer.
But a decent modern computer should work find with typical multitasking jobs during burning. Somethimes I have 10 small background jobs along with the burning. No problem. The only thing I don't do is.. I don't touch the other burner which shares the same cable with my primary burner. I admit that is a stupid thing to try.

Moreover.. DVD's physically damaging the disc because of multitasking? That's a nonsense.
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Old 10-03-2005   #7
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Re: Can a laser make contact and scratch a disc?

Yo-

If I read your post right - it sure sounds like a bad disc not your laser scratching the surface-

If your laser were touching the surface - it seems like it would do it on all the discs you used afterwards-

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Old 10-03-2005   #8
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Re: Can a laser make contact and scratch a disc?

If the Laser would touch the disc at 8x I dont think that you would be able to burn or read any disc afterwards.
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Old 10-03-2005   #9
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Re: Can a laser make contact and scratch a disc?

Quote:
Originally Posted by RWP
After about a year of great service and around 60 writes, my 2500 made it's first "Failed Burn" the other day. It appears that the surface got scratched by contact with the laser or something
Of course the laser beam touches the surface. Why do you think they call it burning? The laser lens itself will not touch discs, unless either the lens carrier or the disc is wobbling around in your drive.

Quote:
This time, however, the burn seemed to be taking longer than normal -- although I was distracted by work I was doing via a KVM switch on another PC at the same workstation -- so can't be sure. I switched back to the PC doing the write and saw that by the progress gauge, the burn should have been complete. But the writer's data activity light was still active.
Could be anything, from a malfunction to an endless loop in the writing process.

Quote:
I gave it a few more minutes to complete the burn but no progress was seemingly made -- so I aborted the burn by using the cancel button in Studio, and Studio promply crashed hard leaving an XP critical error message just before Windows crashed/rebooted on its own. But the drive activity light was off and I ejected the disc for inspection.
When IDE commands fail, they usually fail over the complete data bus. If your harddisk is on the same cable as your writer, these things can happen. Did you update your Operating System to make sure you have used the correct chipset drivers?
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Old 11-03-2005   #10
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Re: Can a laser make contact and scratch a disc?

Quote:
Originally Posted by Mr. Belvedere
Of course the laser beam touches the surface. Why do you think they call it burning? The laser lens itself will not touch discs, unless either the lens carrier or the disc is wobbling around in your drive.
Perhaps I should have been clearer in that statement. I did mean physical contact between the surface of the disc and the laser lens, or some related part the drive can manipulate in relation to the disc. Of course I know that the laser beam itself has no physical substance to it that could cause damage by impact/contact to the surface of the disc. ;-)

Thanks for your info about the likely cause of the crash which followed.
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Old 11-03-2005   #11
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Re: Can a laser make contact and scratch a disc?

I successfully burn @8 over a 100mbit network connection (Network drive). It stops when it runs out of buffer because I disable cache to speed things up (Or it would go like a slug) and then refills the buffer before writing again. I've had no failed burns and the discs read back great.
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Old 12-03-2005   #12
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Re: Can a laser make contact and scratch a disc?

I have a Liteon 1633 that will scratch every disc I burn it if I let nero verify the disc after the burn. So I just use CD Check to verify the data and no problem. I can run nero CDSpeed to test for PI/PO errors and no problem. So the burner burns great I just don't let it nero verify it I just use CD Check. So the laser has to be doing it as it does move up and down to focus. Also all the scuff marks are near the outer edge it never has done it near the inner edge and it's not so much a scratch as it is a circular scuff mark.
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Old 12-03-2005   #13
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Re: Can a laser make contact and scratch a disc?

Quote:
Originally Posted by rwarrin
I have a Liteon 1633 that will scratch every disc I burn it if I let nero verify the disc after the burn. So I just use CD Check to verify the data and no problem. I can run nero CDSpeed to test for PI/PO errors and no problem. So the burner burns great I just don't let it nero verify it I just use CD Check. So the laser has to be doing it as it does move up and down to focus. Also all the scuff marks are near the outer edge it never has done it near the inner edge and it's not so much a scratch as it is a circular scuff mark.
Sounds like what might have happened with mine -- especially the part about scuff marks. (Although in your case it was during a read, correct? I have run Nero Speed many times without a problem). Thanks for the info.

Now I must ask: why/how could any program influence a drive to allow the laser lens to contact the disc? I would think that the drive itself would have a stop in place to prevent the laser from ever getting that close.

And another thing: Assuming a laser lens CAN make contact w/the disc under certain circumstances, wouldn't this cause damage to the laser's focus -- resulting in reduced write/read performance? I realize the lens is likely glass, a surface much harder than the polycarbonate disc. But it can't be a good thing to happen, and eventually, will probably become dirty from polycarbonate dust (or whatever) and not work well.

Thanks for all this great info, guys!
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Old 12-03-2005   #14
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Re: Can a laser make contact and scratch a disc?

Back when I had a CDD3610 burner, I sometimes got scratches from it on the surface of the disc - small scratches about 1 cm long in circular direction. They did not occur on any particular place on the disc. I'm not sure if the drive did this during read or write (this was 5 years ago), but I think it did it mostly during reads.
The drive did still work after a scratch was made.
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Old 12-03-2005   #15
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Re: Can a laser make contact and scratch a disc?

This is an unusual problem and it would be interesting to know just what exactly is happening other then this the 1633 drive works great. If anyone else had a better answer why this happens and it only happens with nero on this drive. I have about a dozen different DVD burners and two dozen CD burners and this is the only drive it has ever done this on. I usually pick up all my drives when they go onsale around $30 bucks so if it quits I will just toss it and no loss. Its just funny how Nero is the only one that it does this with, I have a couple other programs that I burn with and they are fine.
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Old 12-03-2005   #16
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Re: Can a laser make contact and scratch a disc?

I would have to go with Mr B's Idea. if the burner burned the same area multiple times that would look like a scratch. I don't think the burner would operate after touching the disk at high speed.
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Old 13-03-2005   #17
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Re: Can a laser lens make contact with, and scratch a disc?

Quote:
Originally Posted by nmpaulcp
I would have to go with Mr B's Idea. if the burner burned the same area multiple times that would look like a scratch. I don't think the burner would operate after touching the disk at high speed.
In my case, the scratches even appeared in the area that hadn't been written to yet. How could the laser burn a scratch on the disc surface without showing any signs of effecting the dye layer below?

I had pondered the possibility of the laser causing the surface damage before and came to the conclusion that:

1) The clear polycarbonate body of the disc can't react with the laser energy, or the dye layer below would never get written to.

2) If somehow the laser had been overdriven to the point of burning the disc, the first area to be damaged would have to be the dye layer; but there was no sign of damage to the dye layer.

So, at least in my case, at this point I must conclude that the damage was caused by either:

1) A factory defect on the disc.

2) A malfunction of the drive.


In case #2, which applies to the other two drives recently mentioned, the question remains: What can cause a drive to scratch a disc?

In my case, introduction of a foreign object or small particles of debris is not a possibility. I keep it and all discs totally clean of dust and finger prints, etc. Further, I heard no unusual sounds that could indicate major mechanical contact/impact between disc and drive, such as if the disc or platter had been wobbling. (The drive sits only a meter from my left ear when I'm seated at my workstation). There was no imbalance noted, either.

The only remaining possibility then (assuming the disc wasn't already damaged from the factory before I loaded it), is that the drive malfunctioned and drove the laser lense into the disc surface, which because of the small contact patch, might not make much noise. (Just as the sound of friction from a phonograph stylus on a rotating record is very faint -- amplifier off, of course -- the normal operating sounds of the typical drive would likely mask such a slight noise...)

Last edited by RWP; 13-03-2005 at 21:15. Reason: Typo
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Old 13-03-2005   #18
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Re: Can a laser make contact and scratch a disc?

I agree with the contact theory, since it is never in the same spot it must be a moving part inside the drive which would be the laser mechanism it self. Hopefully you can just do what I do, use another program like CD Check to verify the disc with the original data. Like I said the only time it happens is when Nero finishes a burn and does the verify. I always look at the disc before I use it so it not already there and as for noise there is none at all and a few times when it did happen I was able to lighten the scuff mark enough that the disc was still ok.
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Old 13-03-2005   #19
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Re: Can a laser make contact and scratch a disc?

Does the damage look like this? I scanned it and turned the contrast way up to make the scuffs show up better. They are seen best if the image is opened up in the XP Pic and Fax viewer and enlarged a bit. This one won't play, but probably mainly because I aborted the burn before the lead out was written. I can find most of the typical DVD video files in it when analysing it in explorer.
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Old 14-03-2005   #20
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Re: Can a laser make contact and scratch a disc?

Yes they looked about like this and it is not in the dye layer. I don't have any to scan and show you, but this is about how they look.
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Old 15-03-2005   #21
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Re: Can a laser make contact and scratch a disc?

Anyone else seen this kind of damage?

What can cause a drive to navigate the laser lense into the disc?
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Old 15-03-2005   #22
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Re: Can a laser make contact and scratch a disc?

Scratches caused by the lens are very easy to recognize : due
to the high rotation speed, they all follow the track, i.e. they
are circle arcs. From your scan it seems most of your scratches
are of this type, so I guess this is indeed what happened.

It is quite common to get such hits when playing with firmware,
all you have to do is to unbalance the focus loop. On retail drives
this is usually caused by a firmware bug and a very bad disc
(f.i. with very low reflectivity), but PC activity cannot influence it.
Usually drives are robust enough and they can still work ok
afterwards, I hope it's the case for you.
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Old 15-03-2005   #23
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Re: Can a laser make contact and scratch a disc?

I think the most common cause of drive damaged discs we've seen here is caused by the drive dropping the disc while it's still spinning. This would deffinitely be a mal-function in the drive. I don't think it would create the type of scratch that Spath describes, it would depend on the anatomy of the disc tray that it's getting dropped onto. This would also make a deffinite sound, but it could be a fairly faint sound in some cases. In any case, a drive that's doing this should be replaced.
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Old 17-03-2005   #24
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Re: Can a laser make contact and scratch a disc?

finally a thread about this issue. I have nec 3500nd ag which is exhibiting the same issue. My current nec 3500 is my 2nd one as I replaced the first drive due to the same scratching issue. Now I've encountered this scractching problem again on my new drive. I noticed the scratching usually only occurs during reading. Both of the drives were rarely used especially the 2nd one and both drives had firmware version of 2.16.
I would like to test it out more but i don't want to ruin more of my backup data discs.
I wonder if this problem is a known issue at least within NEC as 3500 model was quickly replaced by 3520 model.
edit: i also see an error log "The device, \Device\CdRom0, has a bad block" which i assume was generated while the drive was scratching the heck out my cd.
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Old 17-03-2005   #25
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Re: Can a laser make contact and scratch a disc?

another good thing to look at along with what rdg said is if there are paticles in the tray might have a small piece of grit (grain of salt?) which when the disc is decelerating and being lowered onto the tray will cause the scratch. i had one drive quite a while ago that if you did not wait until spin down the tray would open and the disc would still make a quarter turn. needless to say scratches on the outer edges were rampant with that drive.
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