"William Sommerwerck" wrote in message
...
I don't want to get into an argument over minor points, but...

I'm a non-smoker, and have never lived in an unusually dusty environment.
I'm sure I'm hardly alone in //never// having had to clean an optical-disk
player. (This includes two LV machines, two DVD players, one Blu-ray
player,
an SACD player, multiple computer drives, and I-don't-know-how-many CD
players, including portables.)

I agree that cigarette smoke and cooking vapors (especially oils) are the
most-likely cause of a dirty lens. They get there because they settle
on --
then stick to -- the lens. Plain dust doesn't stick to the lens, so it can
be blown away when the disk spins.

A moving surface drags air with it. (This is why dust tends to settle in
corners -- there's no air motion at those surfaces.) This moving air
should
have //some// effect on non-sticky dust. I believe Geneva (Nortronics)
made
a faux CD with shallow vanes on the surface to increase the air motion.
(It
should be in the garage. I'll look for it.)

In my opinion, a regularly used optical-disk player is not going to
accumulate much, if any, plain dust on its lens. I remain to be convinced
otherwise.

Another point -- has does /any/ contaminant get on the surface of the
lens?
If you argue that it's pulled in by the spinning disk, then... Well, you
draw the conclusion.

* As far as I know, the optical system in most optical-disk players is a
sealed unit.



Modern optical blocks are rarely if ever sealed against getting
contamination inside them. It's actually hard to seal them, unless you have
a window of high optical quality glass under the lens, sealing the top of
the optical chamber. By far the most common arrangement is for the lens to
sit in its suspension, which obviously has to be free to move in all
directions, right over the top of an open-ended vertical tube that leads
down into the chamber which contains the critical angle mirror etc. On some
compact lasers such as are found on slim DVD decks, the lens sits pretty
much right over the top of the open optics. Very early Sony KSS150A lasers
had a 'window' over the optics chamber, and when one of these came in with a
dusty lens, it was the norm to flip the plastic cover off the head, gently
move the lens out of the way with the tip of a scalpel, and clean this
window. Once the '150 was replaced with the '210, the window had gone, and I
don't think any of the (many) KSS series lasers that Sony have produced
since, have had such a window. I seem to recall that one of the early JVC
lasers had a similar arrangement - the Optima 6 or 7B maybe ? - but I might
be wrong on that.

As to your contention that CD lasers shouldn't get dusty because of the air
layer under the rotating disc, it simply isn't right. I'm sure that we've
had this conversation before, and I'm also sure that more than just me has
said that a dusty lens, even on regularly used players, is by far the most
common problem that causes CD players to fetch up on our benches for repair.
The extensive range of Aiwa 3 and 5 disc carousel all-in-ones are
particularly prone to the problem, and over the years have made me a lot of
money in service work cleaning and replacing lasers in them. Lens
contamination from smoke and cooking vapours is not, in my experience, the
"most likely" cause of a dirty lens, it is just an *alternative* cause.
Fairly common, yes, but by no means the *most* common. Plain loose dust 100%
holds that award.

You are right in that DVD players are different in this regard, because of
the high rotational speed of the disc, but then I had already explained that
in my previous post. For sure, on these lasers, film contamination *is* the
most likely cause of a 'dirty' lens rather than loose dust, but as I also
explained, because of the semi-open nature of the optics, the vapour-laden
air will get inside and condense out to coat the optics - including the
underside of the lens - resulting in compromised performance, even if the
lens upper surface is restored to a Windex sparkle.

As to why you have not had a problem with your optical players, I think you
answered your own observation. You are not a smoker, and you don't live in a
particularly dusty environment. Of course you are not alone in this, and I
guess many thousands of people enjoy similar trouble-free performance from
their players, but many others do smoke and do live in a ****-hole, and they
are the ones whose players we see in the world of service. Another factor is
the type of player. I think that from what you have said in the past, you
tend to go for more up-market equipment. Generally, CD and DVD players that
fall into this category, have closed-in unvented cabinets. Basically, except
through the tray opening, there is nowhere for dust and other airborne
contaminants to get inside. However, that's not the case where a player is
integrated into an all-in-one, where they may be in a cavernous enclosure
with a nice hot amplifier in the bottom creating circulating air currents to
carry the dust around that it drags in through the scores of air vent slots
in the base and back. The situation is, of course, further exacerbated by
the inclusion of fans ...

Arfa