added alt.lasers and sci.electronics.repair as a crosspost

"Charles R. Kaiser" wrote in message
...
Hello Group,

This morning I discovered that the CD-RW drive in our sound effects
computer had failed. I noticed this when I tried to play some MP3 files
while I was working. When I looked at the front panel of the CD-RW,
both the "Disc In" and "Writing" LEDs were illuminated. I did a restart
of the system and every thing fired up as normal, then when I tried to
eject the CD from the drive, my system hung.

When I restarted again, Windows failed to fully load. Since the CD
drive seemed to be the problem, I took it out of the machine. The
computer booted with no trouble. I had to use the emergency eject
button to get the CD out of the drive, and when I got it out, I saw the
result of the failure! The "Writing" LED was lit for a reason! The
drive failed with the laser ON! The CD actually has a deformed area on
the surface where the laser was lazing the surface of the disc. This
area carries over to both sides of the CD and the disc surface is cloudy
in an area that covers about 1/6th of the disc's surface.

Has anyone ever seen this happen before? There is no reason that the
computer should have been writing to the CD, it was full and closed to
further writing, but the laser sure did a number on the CD! Very odd.

--
Charles R. Kaiser HOKC - Godtar - http://www.godtar.com
"There's two dates in time that they'll carve on your stone
And everyone knows what they mean. What's more important
Is the time that is known in that little dash in between"

Direct all incoming fire to:
44° 00' 43" N
79° 27' 06" W


1/6 of surface sounds a bit big are to melt for a wee laser even the 30 odd
mW (? IRC) of a CDRW. Wnoder if its heat related otherwise?
A few drives used to have a small fan mounted at back, guess laser diode and
supply run a bit toasty.

Adam

In article ,
Adam Aglionby wrote:

1/6 of surface sounds a bit big are to melt for a wee laser even the 30 odd
mW (? IRC) of a CDRW. Wnoder if its heat related otherwise?

Unless the drive had actually gone into some insane "write mode" where it had
been spraying laser light around while moving the head back and forth. Then
it could have painted a fair area .... ?

--
--------------------------------------+------------------------------------
Mike Brown: mjb[at]pootle.demon.co.uk | http://www.pootle.demon.co.uk/

Adam Aglionby wrote:


1/6 of surface sounds a bit big are to melt for a wee laser even the 30 odd
mW (? IRC) of a CDRW. Wnoder if its heat related otherwise?
A few drives used to have a small fan mounted at back, guess laser diode and
supply run a bit toasty.

Adam


It's all heat related.

50-60mW power at 780 nM (near infrared) (depending upon CD-R vs CD-RW)

under normal use, heats to between 200-700 degrees celsius (also
depending upon CD-R or CD-RW).

Thermal dissipation through the CD, with insufficient dissipation out of
the drive itself, and the cd material (polycarbonate) melts at what
temperature?

50-60 mW is a big ass amount of power, compared to normal read lasers,
or even laser pointers which go up to 5mw.

50mw laser from a DVD recorder:
http://cgi.ebay.com/ws/eBayISAPI.dll...ayphotohosting

50mw OEM Solid State laser:
http://cgi.ebay.com/ws/eBayISAPI.dll...m=5712444 465

Torrance

Unspecified User wrote:
Adam Aglionby wrote:


1/6 of surface sounds a bit big are to melt for a wee laser even the
30 odd
mW (? IRC) of a CDRW. Wnoder if its heat related otherwise?
A few drives used to have a small fan mounted at back, guess laser
diode and
supply run a bit toasty.

Adam


It's all heat related.

50-60mW power at 780 nM (near infrared) (depending upon CD-R vs CD-RW)

under normal use, heats to between 200-700 degrees celsius (also
depending upon CD-R or CD-RW).

Thermal dissipation through the CD, with insufficient dissipation out of
the drive itself, and the cd material (polycarbonate) melts at what
temperature?