CD laser assembly replacement on the cheap

[Gareth Magennis]

Hmm, occasionally I attempt to replace either a laser or complete
laser/motor assembly using cheap generic parts, and it just doesn't work.

Today I recieved 2 x KSM213CCM to replace the ones in a Tascam dual CD
player - DJ type thing with separate remote with pitchbend faders etc.
One works fine, the other doesn't. It clicks, jumps and pops, and sometimes
takes a while to recognise the disk.
(This particular Tascam unit has a built in anti-shock data buffer)

These KSM units contain the laser assembly, the 2 motors and all the
gearing, to move the laser and spin the disc.

I've tried swapping both complete mechs around, and also swapping the KSM
units from one loading mech to the other. Whatever combination/side I try,
the fault is always with the same new KSM unit.
(I made sure the right mounting springs went back in the right place - one
pair are silver, the other gold)

Now these KSM assemblies are really, really cheap off ebay. They have to be
or this just would not be an economical repair. (You can change both within
half an hour)
They are so cheap that I would expect one or two to be DOA on occasion, but
this seems to happen too often. Last time it was another KSM213C that
wouldn't behave.


(I am always very careful in handling these things, I never touch any of the
delicate laser parts/electronics, until they are seated in the loading mech
and the flexible cable plugged into the laser PCB. It is only then I remove
the safety short with desolder braid)


So, a couple of questions.

I assume the laser power preset is adjusted during manufacture and should
not need adjusting after fitting. (I tried turning a few degrees either
way, it did not help)
Could there be some kind of incompatibility with the Tascam player (does it
need its firmware settings readjusted somehow?)

Are these things really just plug and play?

Are these cheapo things often DOA or maladjusted/untested etc?

Have I missed anything else?



Cheers,


Gareth.

[Michael A. Terrell]

Is the soldering iron's tip properly grounded? Our limit at Microdyne
was three ohms form the tip, to the bench's ground connection to the
electrical system.

[Mark Zacharias]

"Gareth Magennis" <sound....@btconnect.com> wrote in message
news:nSI7x.510295$qW.2...@fx20.am4...

I have long suspected the laser power adjustments on the cheapies are
shipped unadjusted - perhaps merely centered.

Mark Z.

[Gareth Magennis]

"Michael A. Terrell" wrote in message
news:8uSdnZdaRdPOcMLI...@earthlink.com...

I'll check that monday. I am starting to wonder if it's me that's killing
these things somehow.

None of them actually died though, they all just wouldn't work properly,
hence all this head scratching.

I'm using this.
http://uk.rs-online.com/web/p/product/5102022/?grossPrice=Y&cm_mmc=UK|Shopping-_-Google+PLA-_-Weller|Soldering+Stations-_-5102022&kpid=&kpid=5102022&istCompanyId=f7e7b05b-2daf-4c0e-8825-3633baf8113b&istItemId=xwiixixli&istBid=tzit&gclid=CJLPxLHG2MUCFUH4wgod9UAAfQ



Cheers,


Gareth.

[Arfa Daily]

>>
>>
>
> I have long suspected the laser power adjustments on the cheapies are
> shipped unadjusted - perhaps merely centered.
>
> Mark Z.
>

I think you might be right Mark. I have also used these cheap complete mechs
for exactly the same reasons as Gareth - that is to make a repair viable. A
couple of months back, I had a major fight with an eBay supplier over one
that didn't work. It actually looked like someone had been having a go with
a poker on the board on the back of the optical unit.

I contacted the supplier, and told him that the unit did nor work, right out
of the box, and it looked like someone had taken a poker to the soldering.
He replied and tried to tell me that it was just typical lead-free soldering
that I was looking at, and that I should just turn up the gain pot and it
would work just fine. I politely told him that I had been repairing CD
players since the day they were released onto the market in the 80s, and I
could tell the difference between lead free solder, and someone having been
at it with a nail heated up on a gas ring. I also told him that there wasn't
a gain pot.

He replied again and said that there was nothing wrong with the soldering,
and I should adjust the gain pot on the back of the laser. So I sent him a
photo of the shit-street soldering, and told him that the pot on the back of
the optical block was not a gain pot, but an adjustment in the feedback loop
for controlling the output power of the laser diode, and that on Sony
lasers, it should not be adjusted willy-nilly, otherwise damage to the laser
diode could easily be done. I further assured him that I had sufficient
experience of replacing lasers to be able to say with absolute certainty
that this one was faulty, and that I would like it replacing please. And
still he went on about adjusting the "gain pot", finally suggesting that I
send the whole piece of equipment back to him, and he would repair it for me
...

At this point, I got really mad, and asked him if he really thought that I
was trying to have him over for eight fucking quid ???!!!

Eventually, he sent me another, and that worked ok immediately, but
significantly, these cheap replacements never seem to have the 'normal'
paint blob on the pot. I seem to recall also that the original Sony lasers
had a little dot matrix printed label on them that had some figures, amongst
which were the factory-measured laser current ??

So maybe these ones *are* being shipped unadjusted ... With most
manufacturers, 1 volt p-p eye pattern at the RF test point seems to be an
'unwritten' standard so might be worth checking next time one of us fits one
of these.

Arfa

[thekma...@gmail.com]

CD players were never intended to be designed to last. The developers
of ARPA-NET(predecessor to the Internet) KNEW, forty years beforehand,
of its potential and of the ultimate culmination: the CLOUD.


CDDA(Compact Disc Digital Audio) was just a teaser, a temporary stand-in
for the ultimate transition of all media(music, movies, TV, books, and news)from
their physical form to a server-based access point.


I frequent retailers in the second-hand industry("thrift stores"), and of every
ten CD or DVD players donated, only TWO actually work! They were built
flimsily ON PURPOSE, because manufacturers know what was coming next -
mp3s, WAVs, Napster, iTunes, NetFlix, and the Cloud. You never see
anyone in "Star Trek" insert a disc or tape into a machine to play something
back, do you? Welcome to Star Trek my friends! It's here(we just need
to figger out how to build those cool ships...).


I still hold on to my physical collection and the gear to play it on
because I believe in something that everyone else has forgotten about -
BACK-UP. And also, music & movies physically played back just plain
sound and look better!