b said:
Arfa Daily ha escrito:
...that was because I didn't consider the machines in question broken.
Disagree. I still have 3 machines which I restored in this way going
strong after 4 years, 4 years and 3 years respectively. (Philips, Sharp
and a no-namer) plus another I gave to a friend last year which I
believe is still operating fine.
I know the laser pickups commonly fail, and in a high proportion of
machines the power supply is the other main culprit. Ribbon cable
failures resulting in 'no disc' errors I have seen a few times of late
too. However, the point I was trying to make is that as with any
optical device, cleaning is critical to proper operation and is a
common reason for failure.
...certainly is a 'fundamental try' (sic), especially for a
non-technical person who would doubtless be able to do little else.
more so if the unit isn't used that often (in which situation, your
theory as to the dust being blown off is flawed). Hence: cleaning is
worth a try before condemning it to the landfill. Since the OP wanted
to choose between 'cleaning or throw away', I just think you should
have put that more clearly in your post, it might have been more
helpful.
Ok Ok, let's not get all defensive! ;-) I do take your point though
that dvd players tend to fail more due to psu and laser failure.
but ....(lasting) repair unlikely - why not? experience shows it's
perfectly possible, especially if the laser unit was OK and dirt really
was the cause of the problem, in which case there's no reason why the
unit couldn't go on working for another few years, at least 'till
cleaning is required again!
-B.
All-righty. I guess we could argue about this all day - and I've got lasers
to change ... !!
The reason that I said that any fix produced by cleaning was unlikely to be
lasting, is because if dust has managed to settle on the lens - and the
rotational speed of the disc *does* produce a very strong wind at the lens,
trust me on this, I have it on good authority from a manufacturer whose
training course I did - then there will certainly be dust settled on the
critical angle mirror and the face of the pickup diode array. And before
someone says that in some laser arrangements, the pickup diodes are not flat
in the bottom of the optical block, I know this ...
Any dust on the internal optics will not be able to be removed by any
cleaning method commonly employed in workshops. Thus, any improvement
achieved by cleaning the optics that you can get at, is likely to be
compromised in the long term, by the dust that you can't.
I used to clean the lenses on DVD players, with varying degrees of success -
initially - but an awful lot of the ones that seemed to be cured, came
bouncing back a couple of months later, in trouble again. This often results
in an irate customer, and more so if the warranty on the repair has just
expired. Is it worth it ? For the same reason, these days, I seldom rely on
just cleaning of CD lasers. Most are so cheap, that you may as well just
replace them, rather than risk losing a customer. Of course you will be able
to find exceptions that prove the rule, and I'm sure that there are ones
that I've cleaned, which are still going strong.
However, if dust has settled on the pickup diodes, the output balance is
quite likely to be affected, unless there is a perfectly even layer of dust
across the whole array. There is a limit to how much slack can be taken up
by the servo circuitry, even on players where this is done automatically.
DVD is a technology that works by the skin of its teeth, with a fair wind
behind it. It doesn't take much upset in the system to compromise this.
Again, I didn't tell the owner not to clean it. He asked if he should, and I
merely told him that it was unlikely to effect a cure. Perhaps he can tell
us if it did any good ? If it did, fine. If it's then still going in a few
months - better. He will have been one of the lucky ones. But to everyone
else reading this, I still stand by what I said, for the additional reasons
given.
As far as power supply trouble goes, I would agree that this is also a very
common failure area, but in the case of Philips machines, it's ( almost )
invariably a short circuit secondary rectifier, which results in the psu
going into cyclic shutdown, giving a machine that's dead, to all intents and
purposes, rather than one that's just refusing to play discs.
Didn't you like " fundamental try " ? I was using the phrase in a sort of
'spoken speak' rather than 'written speak' ... conversational maybe ?
d;~}
Arfa
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