18 Sep
2006
18 Sep
'06
3:41 p.m.
At 02:35 PM 9/16/2006, CRC wrote:
It should be very easy to check this. Those IR detector cards sold for
testing TV remote controls will detect a CD player or CD-ROM laser. Has
anyone tried holding one over the pickup of a CD-ROM drive?
I know for a fact that my ancient Philips external drive, which is
actually based on an audio CD player, turns off the laser when not
required. When there's a chance you've inserted a disk, it powers up the
laster, tries to find the focus point, if it finds it, it spins up the
disk and reads the TOC. If not, it powers down the laser. This is, I am
pretty sure, shown in the service manual.
-tony
The basic problem with commercial CD
burners/players is that they
keep the laser diodes on when powered, although at the low power
required for reading. The life of run-of-the-mill laser diodes is on
the order of 10,000 (10.000) hours. Consequently, if you keep your
system on all the time you can expect one to two years of useful life
from the beast (some longer, some shorter). From <http://www.wtec.org/
loyola/opto/ad_rohm.htm>:
That document dates from 1994. You'd think that manufacturers would
want to increase MTBF and eliminate failures as quickly as possible,
so I find it hard to believe that LEDs are left on inside today's
CD/DVDs just because it's hard to turn them off and they don't want
to improve lifetimes. This info may be entirely relevant for
1980s drives, who knows? What sorts of other ancedotes and
claimed facts do we have?