CD Problem

[Stan Brown]

This part:

So then there is no way to just identify the proper controller. You
actually have to delete things. Wow!

 

[Antares 531]

I know, but it took a while to find a CD drive like my failed one that
I could swap.

We got the flawed CD drive installed into my friend's computer, and it
can't write in this setup, either, so, obviously, the drive is flawed.
Probably a laser failure, but what ever, it is ready for the Dempster
Dumpster.

 

[GreyCloud]

The principle of how a CD/DVD works, is described here.

http://www.maxim-ic.com/app-notes/index.mvp/id/2947

The CD uses one laser. The DVD uses the other laser. Two lasers
total on a CD/DVD drive. As far as I know, once one of the
lasers is selected, it's used for everything with that piece
of media. Since writing requires highest light output, a
performance deviation on the laser should first show up as
flaky recording.

Or no recording at all.
It still takes a bit more power to do the burning process, otherwise
doing a read would cause problems.
Do I have that part correct?
It has been a long time since I was last doing automated test engineering.

The laser driver chip can be connected to the CD laser,
or to the DVD laser, but not both at the same time. The diagram
on that page, shows a two position switch, so that the output
of the summing block, goes to either one laser or the other.
When you insert media, the drive may have to probe with
both lasers for a short period of time (one at a time),
to get a handle on what kind of media is installed.

The power level to the laser, varies when you're writing
with the laser. This diagram is intended to show writing.

http://www.maxim-ic.com/images/appnotes/2947/2947Fig01.gif

They don't have a diagram for reading. According to the text
on that page, when the *same* laser is used to read, it
is modulated with a sine wave coming from an RF oscillator.
(The power level should be less than the power level to
erase or write.) A possible reason for doing it that way, might be
for synchronous amplification of the returned photodiode
signal. For example, in this figure

http://www.maxim-ic.com/images/appnotes/2947/2947Fig04.gif

the RF amplifier on the right, used for reading, could
be a "tuned" amplifier (perhaps a trans-impedance amplifier)
that only responds to a signal in a certain narrow frequency range.
That avoids competition from stray light sources. The RF amplifier
on the right, would operate at the same frequency as
the RF oscillator shown in figure 3.

*******

This is a datasheet for a similar device. The figures near the
end of the document, show how reading and writing are a
continuum. The read current from the RF oscillator, is at
around 375MHz.

http://www.datasheetcatalog.org/datasheet/zarlinksemiconductor/zarlink_ZL40514_FEB_04.pdf


*******

Blu Ray would need a third laser. Each tech has different
optical requirements.

http://www.tgdaily.com/files/images...dvd_blu-ray_read_write_method_comparisons.jpg


Paul

Maybe I got a hold of a very old site explaining how dvds work. But you
do need a higher output to burn a cd, and if his (the op) stated
correctly that when he tried to burn a cd he got an error message, then
there is something very much wrong in the electronics that controls a
single laser output. Hard to tell. Do you find any diagnostics
software for his cd? If you do let him know where he can get it and run
the diagnostics. Hardware/software are co-dependent.

 

[GreyCloud]

This must be the problem. I plan to go to Best Buy this afternoon and
buy a new CD drive. Then if this doesn't solve the problem I'll have a
spare on hand, anyway.

I'm not settled, yet, as to what brand, type of CD drive I should buy.
I really don't need the extended functions of a DVD+R drive, but I do
have a new pack of those CDs on hand.

I wouldn't know what brand to get. I've never had to replace them. The
one in my old IBM is over 12 years old and still works. The one in this
Sun is over 10 years old and still works.

 

[Paul]

Or no recording at all.
It still takes a bit more power to do the burning process, otherwise
doing a read would cause problems.
Do I have that part correct?
It has been a long time since I was last doing automated test engineering.

I'm just going from what I can get from reading some chip info. I presume
the write/erase values are a lot higher than read, as you wouldn't want the
read operation to upset things.

Maybe I got a hold of a very old site explaining how dvds work. But you
do need a higher output to burn a cd, and if his (the op) stated
correctly that when he tried to burn a cd he got an error message, then
there is something very much wrong in the electronics that controls a
single laser output. Hard to tell. Do you find any diagnostics
software for his cd? If you do let him know where he can get it and run
the diagnostics. Hardware/software are co-dependent.

I'm not aware of any diagnostic software. If there was any, it would be
pretty popular.

There used to be a site, with some nice pictures of disassembled head
assemblies, but with the state of search engines now, I couldn't find
that either.

Paul

 

[GreyCloud]

We got the flawed CD drive installed into my friend's computer, and it
can't write in this setup, either, so, obviously, the drive is flawed.
Probably a laser failure, but what ever, it is ready for the Dempster
Dumpster.

From looking at my Sun cd/dvd burner... it has four lasers in it. One
for read, one for write... and the same for the dvd side. Obviously an
older drive. From what I could gleen, industry has found a way to
reduce the parts count and make one laser do double duty... the old
industrial short cut to make the drive cheaper.

 

[GreyCloud]

I'm just going from what I can get from reading some chip info. I presume
the write/erase values are a lot higher than read, as you wouldn't want the
read operation to upset things.


I'm not aware of any diagnostic software. If there was any, it would be
pretty popular.

There used to be a site, with some nice pictures of disassembled head
assemblies, but with the state of search engines now, I couldn't find
that either.

I wonder if that has anything to do with Google changing their search
engine to weed out what they think are low quality websites?
I've heard that about 12% of returns are now omitted.

 

[Char Jackson]

I wonder if that has anything to do with Google changing their search
engine to weed out what they think are low quality websites?
I've heard that about 12% of returns are now omitted.

According to Google's press release, they only weeded out results
where sites were essentially just copying content from other sites. If
true, we shouldn't be missing anything.

 

[GreyCloud]

According to Google's press release, they only weeded out results
where sites were essentially just copying content from other sites. If
true, we shouldn't be missing anything.

Oh, I hope so!