"Maxmel" wrote in message ...
Hi , I'm just wondering if it's possible to adjust or at least verify the
laser of a DVD or CD player without a laser beam checker.

I have a 500MHz scope and a god expertise in electronics but never play
with DVD/Cd laser Assy.

Problem is the DVD player doesn't play always the DVD inside , lens has
been cleaned.

I'm assuming that these steps are standard for all tha models.

Also , what is the difference between the laser of a DVD and a CD ?

Why a DVD laser can read CD and not the inverse.

Thanks a lot for your help.


There's not really much you can do to make a definitive assessment of a
laser's condition, other than to rely on experience and substitution. Unless
it is part of a manufacturers service setup procedure - Pioneer CD players
for instance - the laser power pots should NEVER be adjusted from their
factory set, and usually sealed, positions. Even a laser power meter won't
tell you a lot about a laser's condition. Even if it indicates that the
emitted power is within spec, plenty of laser problems are caused by
defective pickup chips ( the clear plastic chip usually at the bottom, which
has the individual photo diodes on it ) or dust on the internal optics,
diffusing the reflected beam from the play surface, before it gets to the
pickup chip.

The difference between a CD and a DVD laser, is wavelength and power. A DVD
laser is in the visible red portion of the spectrum, and of higher emitted
power than a CD laser, which is in the infra red part of the spectrum. DVD
lasers do not read CDs or vice versa, in general. Rather, there are two
laser emitter chips, for the two different wavelengths, and usually a single
pickup chip, although these items are all integrated together in a single
pickup head assembly.

If your player handles CDs ok, but struggles with DVDs, theres a better than
80% chance that the problem is the laser.

Arfa