In article ,
curls wrote:
My car's CD player reports Check CD and ejects many CDs. I've managed to get the radio out of the car, and
opened it until I can now see the laser lens.

I plan to clean with Qtip and isopropyl alcohol 91%.

Use a photographer's "puffer brush" first (a rubber squeeze-bulb with
a soft-bristle brush on the end). Brush the lens very lightly and
then puff it gently with air. This will dislodge and remove the worst
of the dust.

I would recommend getting electronics-grade isopropyl rather than
using 91% commercial type... you really want something as pure as
possible so that it won't leave a residue.

Is there anything else I can clean? Or lube with white lithium?

The only other thing I see which you might address, is the metal rail
on which the optical sled moves in and out. If I'm seeing what I
think I'm seeing, it's the silver metal rod, which has something that
looks like a helical spring wound around it.

If this rail is dirty, or if it has old lubricant which has gotten
gummy, the sled would be unable to move smoothly and the
laser/photodiode mechanism would have trouble following the spiral
track on the CD's data layer.

You might be able to clean it (very carefully) using a small brush
with a suitable solvent (electronics-grade isopropyl, or "white
spirit" (naptha), and then relubricate (a *small* amount of sewing
machine or watchmaker's oil... "light machine oil"). Do *not* use
3-in-1 or WD-40! Be very careful not to get either the solvent or the
oil on other parts of the mechanism, or force or bend anything.

Due to the presence of that helical spring or coil (whatever it is I
think I'm seeing) this is likely to be a tricky process. Don't try it
at all unless you're willing to take the risk of destroying the whole
thing.

If you can get a long disc (70-80 minutes) to play all the way to the
end, and then cut the power without pressing "STOP", you'll probably
find that the laser sled has moved all the way to the outer diameter
of the CD. This may leave the "rail" exposed, and easier to access
and clean.

You might find that some gunk has built up near the inner diameter of
the rail. This could "bind" the optical sled when it tried to read
the disc's table of contents, which is written right at the inner
diameter of the CD data area.

There are disks that consistently read without trouble. The same disk will work every time. It's been only
4 out of about 20, but it's the same 4 CDs every time that get initially picked up just fine. The rest of
the CDs have trouble and will eject with Check CD repeatedly. Then on one of the re-inserts, they'll read.
The CDs are books on CD from the library. I've washed most of them, and they look good (not scratched or
dirty).

Books-on-CD are commonly "burned" CD-Rs, rather than "pressed" CDs.
The reflectivity contrast of their data patterns is about half that of
pressed CDs, which means that the laser/photodiode has a weaker signal
to follow. It's fairly common for failing CD players to start
rejecting CD-Rs, while they can still track commercial "pressed" CDs.

This sometimes (often?) means that the laser diode is approaching its
end of life - the laser output is declining, and the photodiode system
is getting a weaker and weaker signal from the disc.

The only real cure for this is to replace the laser diode (often the
whole optical assembly), and then recalibrate the laser drive and the
tracking. This is definitely possible but may not be economically
worthwhile. There are probably YouTube videos which show the
procedure.

It's sometimes possible to turn up the laser drive current, but this
is a *very* temporary hack... the higher current just makes the diode
fail all that much sooner.