Why CD laser unit fails so often?

[Miguel Giménez]

Hi

In the last years I have changed twice the laser unit of my Aiwa CD
reader and once the unit of my mom's Sony reader. The three were
original spare parts, and the three died months after.

Why this happen? Do I need to adjust laser current after change? Are
they basically unreliable?

TIA

--
Regards
Miguel Giménez

[pf...@aol.com]

Never had or observed this problem per-se. Many times I have seen the output level of the laser poorly adjusted, poorly focused or not precisely aligned, especially if resulting from a home repair. Admittedly a small sample, perhaps about 20 players in all.

Peter Wieck
Melrose Park, PA

[Miguel Giménez]

The replacements worked OK for some months, then failed abruptly. The
symptom was always: insert disk -> some seconds trying to read disk ->
disk ejection. May be a focus problem unrelated to laser?

Also, there were neither smokers nor floating dust near the devices.

--
Regards
Miguel Giménez

[pf...@aol.com]

On Wednesday, May 31, 2017 at 12:34:50 PM UTC-4, Miguel Giménez wrote:

May be a focus problem unrelated to laser?

Likely.

[Trevor Wilson]

On 31/05/2017 10:29 PM, Miguel Giménez wrote:
> Hi
>
> In the last years I have changed twice the laser unit of my Aiwa CD
> reader and once the unit of my mom's Sony reader. The three were
> original spare parts, and the three died months after.
>
> Why this happen? Do I need to adjust laser current after change? Are
> they basically unreliable?
>

**IME modern lasers are not reliable devices. The older ones were very
reliable. Why? Dunno exactly. If you look at an old laser from a Sony or
a Philips CD player, you will likely see a very carefully (hand
assembled?) laser unit, constructed from carefully machined aluminium
alloy, precisely aligned, using a high quality glass lens. Replacement
cost typically ran to several hundred Dollars. Modern lasers are all
made in China, from plastic and steel and are almost certainly machine
assembled. Cost, typically runs at around $20.00 or so. With massive
cost reductions in any product, something usually has to give.


--
Trevor Wilson
www.rageaudio.com.au

[ohg...@gmail.com]

On Wednesday, May 31, 2017 at 8:30:01 AM UTC-4, Miguel Giménez wrote:

Don't know about your particular drives, but anybody who did any kind of audio work in the 90s knows that Sony lasers were/are pure, unadulterated shit. I'm being kind here.

There were tons of otherwise very nice Aiwa three CD carousel combo stereos that had decent power and respectable sound (given the market) and enough LEDs flashing to keep the Walmart buyers enthralled. Unfortunately, they all came equipped with Sony lasers. We pulled the plug on doing these after the first few failed and recommended that our customers use these for "garage" radios.

Now I've heard that there were/are Chinese counterfeits for these and this might explain repeat failures, but it doesn't explain why so many Aiwa and Sony brand CD players came in for weak or dead lasers in two years.

[whit3rd]

On Wednesday, May 31, 2017 at 11:50:43 AM UTC-7, Trevor Wilson wrote:
> On 31/05/2017 10:29 PM, Miguel Giménez wrote:

> > In the last years I have changed twice the laser unit of my Aiwa CD
> > reader and once the unit of my mom's Sony reader. The three were
> > original spare parts, and the three died months after.
> >
> > Why this happen? Do I need to adjust laser current after change? Are
> > they basically unreliable?

> **IME modern lasers are not reliable devices. The older ones were very
> reliable. Why? Dunno exactly. If you look at an old laser from a Sony or
> a Philips CD player, you will likely see a very carefully (hand

> assembled?) laser unit...

Usual failure mode for a surface-emitting laser is some kind of dirt migration in the
surface. This has NOT been getting worse, the chemistry and material preparation
is as good now as it has ever been, and even UV semiconductor lasers are working
well for long periods of time.

Another possible reason for failure is ... lack of use. The normal electrical bias during
operation is intended to keep sweeping impurities out of the sensitive region.
If you just store the unit on the shelf, and DON'T operate it for a few hours
a week, the (equivalent of) dust bunnies just pile up.

The implication is, use your CD/DVD/BD readers and burners every week or so. They
might just go bad on the shelf otherwise.

[Miguel Giménez]

Certainly the Sony unit was seldom used, and the Aiwa use was greatly
reduced after first failure to preserve the laser (sigh!). In both units
the new part failures happened after some weeks of inactivity.

Thank you.

--
Saludos
Miguel Giménez

[Jeff Liebermann]

On Wed, 31 May 2017 14:29:47 +0200, Miguel Giménez <m...@privacy.net>
wrote:

This might be more than what you might want:
"List of failure modes and mechanisms in Laser Diodes"
<http://www.diee.unica.it/~vanzi/ListFailures1of2.pdf>
This is from 2004, so some things will be out of date. The chart on
Pg 2 showing various failure mechanism might be a good start. I
haven't had time to read through the report.

What little post mortem testing I've done seems to point to a
deterioration in laser output, but I've never investigated further and
some crude measurements using a flat photodiode as a light meter.

This may also be helpful:
"Notes on the Troubleshooting and Repair of Compact Disc Players and
CDROM Drives"
<https://www.repairfaq.org/REPAIR/F_cdfaqd.html>

--
Jeff Liebermann je...@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

[Miguel Giménez]

El 09/06/2017 a las 19:16, Jeff Liebermann escribió:
> On Wed, 31 May 2017 14:29:47 +0200, Miguel Giménez <m...@privacy.net>
> wrote:
>
>> In the last years I have changed twice the laser unit of my Aiwa CD
>> reader and once the unit of my mom's Sony reader. The three were
>> original spare parts, and the three died months after.
>>
>> Why this happen? Do I need to adjust laser current after change? Are
>> they basically unreliable?
>>
>> TIA
>
> This might be more than what you might want:
> "List of failure modes and mechanisms in Laser Diodes"
> <http://www.diee.unica.it/~vanzi/ListFailures1of2.pdf>
> This is from 2004, so some things will be out of date. The chart on
> Pg 2 showing various failure mechanism might be a good start. I
> haven't had time to read through the report.
>
> What little post mortem testing I've done seems to point to a
> deterioration in laser output, but I've never investigated further and
> some crude measurements using a flat photodiode as a light meter.
>
> This may also be helpful:
> "Notes on the Troubleshooting and Repair of Compact Disc Players and
> CDROM Drives"
> <https://www.repairfaq.org/REPAIR/F_cdfaqd.html>
>

The first link is too technical, even for a physicist like me.

The second is very helpful, although somewhat discouraging. I'd like to
know if recent Sony spare parts are more reliable than eight years ago
or it's better to toss the devices and buy better ones (Denon?).

[pf...@aol.com]

On Tuesday, June 13, 2017 at 7:54:47 AM UTC-4, Miguel Giménez wrote:

> The second is very helpful, although somewhat discouraging. I'd like to
> know if recent Sony spare parts are more reliable than eight years ago
> or it's better to toss the devices and buy better ones (Denon?).

I don't know. At this point, I have six (6) CD changers and one single-disc player in the inventory, Five changers are Sony, including two 200-disc changers, one is a Yamaha. The single disc player is a Revox. None of them have had any laser problems over the last many years of use. One of the 200-disc changers has run for weeks at a time 24/7 as it feeds my transmitters, mostly in the winter. All the Sony devices are thrift-shop purchases for US$25 or less, so not even 'babied-from-new' as is the Yamaha, or second-owner as is the Revox.

So, I suspect some sort of user-error, installation problem, drifting focus and/or counterfeit part issues happening here. All of which are entirely possible and nothing to be ashamed over.

http://www.ralph-toman.de/cd_player_eng/cd_player_eng.htm is a rather technical discussion on "how-to" do the various adjustments for various CD players that might be helpful.

Best of luck with them.

[John-Del]

On Tuesday, June 13, 2017 at 8:22:46 AM UTC-4, pf...@aol.com wrote:

>
> So, I suspect some sort of user-error, installation problem, drifting focus and/or counterfeit part issues happening here. All of which are entirely possible and nothing to be ashamed over.
>

> Peter Wieck
> Melrose Park, PA

If only. I stopped repairing CDs when the prices dropped to a certain level, but Sony lasers, at least in the lower end machines, are and were junk. Since I've bailed on repairing them many years ago, I've read stories in our private association site of other servicers still repairing them having several new Sony sleds DOA or having other issues. These are most likely aftermarket or counterfeit as I can't believe Sony would still be making replacement parts.

None of this excuses the original parts that failed in great quantity, or addresses the possibility that higher end Sony CD players (changers for instance) didn't use a better quality laser assy that were not short lived. Only by knowing production numbers and comparing them with repair statistics could we shed any light on them.

[Foxs Mercantile]

On 6/13/2017 8:23 AM, John-Del wrote:
> I stopped repairing CDs when the prices dropped to a certain
> level, but Sony lasers, at least in the lower end machines,
> are and were junk.

<http://www.theonion.com/video/sony-releases-new-stupid-piece-of-shit-that-doesnt-14309>



--
Jeff-1.0
wa6fwi
http://www.foxsmercantile.com

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