Bob said:
I have a used DVD RW drive that behaves strangly. It works fine for reading DVDs
and CDs and writes CDs fine. It shows in "Computer" as "DVD RAM drive" when no
disk is inserted. Upon inserting a CD or DVD R disk, it goes to displaying as
"CD drive". I can drop files to be written to the drive into it as long as it
does not have a DVD R disk inserted into it. Insert a CD, fine. Insert a DVD,
and I get an error msg "Windows encountered a problem when try to copy this
folder". Without a DVD inserted, it accepts the files fine, and displays the
write file option. Insert a DVD, and the write option goes away. Insert a CD -
everything is fine.
Is this just a bad drive?
Like, dirty DVD laser/lens ?
http://upload.wikimedia.org/wikipedia/en/e/eb/Dismdvd.jpg
*******
DVD uses 650nm light. CD uses 780nm light. The first is
"red", the second is "infrared". Even if your eye cannot
see the "infrared" case, any video camera type device with
silicon sensor can see infrared (even on units that have
an infrared filter to prevent that).
http://upload.wikimedia.org/wikiped....svg/512px-Comparison_CD_DVD_HDDVD_BD.svg.png
The power level of the light source is variable. It is
continuously programmable. On the surface, you might see
references to "read/write/erase" power levels. But the media
itself might report how much energy is needed for the particular
media.
With the drawer closed, and no media present, there might be
no light. When the drawer opens and closes, the drive probably
doesn't have a way of detecting media is present. Turning on
the various lasers, one at a time, and scanning for a reflection,
would tell the drive something is there.
http://upload.wikimedia.org/wikiped...g-cutaway3.JPG/640px-Dvd-burning-cutaway3.JPG
So at least with the DVD detection case, you'd see red light,
while with the CD case, you'd need to view the thing with
a video camera, to see a "bright" source present. Monochrome
cameras have the infrared filter removed, while color
cameras have an infrared filter in place (to prevent throwing
off the color viewed, when viewing in sunlight). Some security
cameras, the infrared filter "switches out" when going to
night mode.
I also have a kind of strip purchased from RadioShack for $5,
which is an infrared detector. It's good for verifying a signal
is coming from an infrared remote control. But not good enough
for detecting a CD laser. But a video camera or even a webcam
may help there.
Since it is looking for a reflection, there would be a laser light
source, some sort of lens to focus the photodetector, and a
photodetector to receive the light. Even if you see the lasers
at work, it doesn't mean the photodetector is getting anything.
Photodetectors can die too. Like, if you deliver a static discharge
to them. If the previous owner was a smoker, maybe over time
some optical surface could have crud deposited on it.
*******
In terms of media differences, DVD-R or DVD+/-RW would have
a spiral groove pressed into the disc. The laser tracks
that spiral groove, so as the drive is reading, the head assembly
is constantly on the move, tracking the groove.
DVDRAM media consists of concentric circles, like the concentric
tracks on a hard drive. So the tracking task for the drive is
quite different (it still needs to track, if the media is off-center).
I've never owned any DVDRAM media, so don't know a thing about them.
I have two DVDRAM drives here (LG GH22 and GH24 series), and the
icon in WinXP changes when media is detected. With no media present,
they're identified as DVDRAM capable drives.
If you pull DVD-VR media from a "video recorder" device, the format
may not be recognized properly by WinXP. So when doing your tests,
start with a blank and see if a blank is recognized as a blank.
Things like the free Nero InfoTool can display information
about inserted media - that's assuming media is being detected
at all. The InfoTool also displays the capabilities the drive
claims to have. InfoTool was written by a separate developer,
and at one time, the tool was distributed from the developer's
web site as well. I think currently you could download it off
some Nero FTP site if you wanted a copy. It's treated as a
utility.
For example, this drive is not DVDRAM capable. The "Disc" tab
in the bar, is where you get info on freshly loaded media (like
get the media tag off a blank piece of media). The InfoTool graphics
keep changing, and this is a particularly old version.
http://screenshots.en.sftcdn.net/en/scrn/22000/22234/nero-infotool-1.jpg
Paul