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Sony laser questions

I received a Sega CD (old model with the motorized tray), and had some
questions..

When I first got it, putting in a CD resulted in the sound of the
motor spinning up, stopping, spinning up, stopping, then the Sega CD
reported NO DISC.. So, I took the unit apart, and was stunned to see
what I saw the thing do.. When it first spun it up, it stopped, then
the disc spun in reverse, then gave up with the NO DISC message.

The laser in the unit was a Sony KSS-240A.. I then proceded to turn
the three POTs, one at a time, VERY slowly, like 1-2 degrees (maybe
3), and if it didn't help, I went the other way, and if that didn't
work, i'd return it as closely as I remembered it's position, then go
to the other POT...

Well, after all three POTs, non of them helped, still had the weird
erratic actions... Then, I remember someone telling me the 240A has
TWO lenses, one on the top, and one on the bottom.. So, I took the
plastic piece off, carefully lifted up the lens, and blew into it..

After that, the machine has been reading games, and music CDs... But,
at one point in a certain game, when it played a certain CD audio
track, it did the weird "spin up, spin down" thing, and decided to
freeze the whole game up.. I try again, at the SAME audio track it
did the same thing.. So I cleaned the CD, and then it worked
perfectly..

My question: Could messing with the POTs made it more sensitive to
smudges on a CD? Or are the 240A's just weak lazers? My Sony boombox
has the same KSS laser, and it used to do the SAME thing, until I took
compressed air at it's lens..

Also, though I did put the POTs back in their original position, I
fear 1, 2, or all 3, may be 1-3 degrees off from their original
position.. Can this hurt the system?
 
A

Arfa Daily

I received a Sega CD (old model with the motorized tray), and had some
questions..

When I first got it, putting in a CD resulted in the sound of the
motor spinning up, stopping, spinning up, stopping, then the Sega CD
reported NO DISC.. So, I took the unit apart, and was stunned to see
what I saw the thing do.. When it first spun it up, it stopped, then
the disc spun in reverse, then gave up with the NO DISC message.

The laser in the unit was a Sony KSS-240A.. I then proceded to turn
the three POTs, one at a time, VERY slowly, like 1-2 degrees (maybe
3), and if it didn't help, I went the other way, and if that didn't
work, i'd return it as closely as I remembered it's position, then go
to the other POT...

Well, after all three POTs, non of them helped, still had the weird
erratic actions... Then, I remember someone telling me the 240A has
TWO lenses, one on the top, and one on the bottom.. So, I took the
plastic piece off, carefully lifted up the lens, and blew into it..

After that, the machine has been reading games, and music CDs... But,
at one point in a certain game, when it played a certain CD audio
track, it did the weird "spin up, spin down" thing, and decided to
freeze the whole game up.. I try again, at the SAME audio track it
did the same thing.. So I cleaned the CD, and then it worked
perfectly..

My question: Could messing with the POTs made it more sensitive to
smudges on a CD? Or are the 240A's just weak lazers? My Sony boombox
has the same KSS laser, and it used to do the SAME thing, until I took
compressed air at it's lens..

Also, though I did put the POTs back in their original position, I
fear 1, 2, or all 3, may be 1-3 degrees off from their original
position.. Can this hurt the system?

KSS240A lasers are for sure not the most reliable in the world. The pots on
there are factory set and sealed, and should not be adjusted. With most Sony
lasers, even a modest over-drive of the laser diode can do it permanent
damage, so I would not recommend anyone to attempt adjustment, unless it is
a last ditch "do or die" attempt to prove that the laser is worn out. The
dust that you are blowing by going down the side of the lens, is likely
laying on the critical-angle mirror that's down there, and if that is the
case, there is probably a similar amount of dust on the pickup diode array,
which likely won't be dislodged by air-blowing. This dust will also degrade
the performance of the laser, and I would think that when a small amount
builds up on the mirror as well, that is enough to tip the performance over
the edge, and stop it working.

Blowing the dust off the mirror, just about gets the performance back up
for a couple of months to the point where the external circuitry can handle
the reduced level signal output that the dust is causing. Sensitivity to
marks on the disc, and failure to play with the disc spinning backwards, are
both typical symptoms of a worn or faulty laser.

Personally, I would just go ahead and replace it. Although not one of the
cheapest of the Sony KSS series lasers, it never-the-less is not
prohibitively expensive either. The only thing that I would warn against, is
using a generic 240A substitute, such as an NKS240A. Although most cheap
subs for the KSS series work just fine, I have found that in many
applications using the '240, only a genuine Sony original will display the
performance required for reliable operation.

Arfa
 
Ok, thanks for the information..

Since I did mess with the POTs, and they are probably 1-3 degrees off
a little, will this cause major problems in the long run? Right now
it seems to work at the moment, as long as the CD is spotless...
 
A

Arfa Daily

Ok, thanks for the information..

Since I did mess with the POTs, and they are probably 1-3 degrees off
a little, will this cause major problems in the long run? Right now
it seems to work at the moment, as long as the CD is spotless...

As long as it is working at the moment, it is unlikely that you have done
any long term damage. Although the settings of the pots are quite critical
( two of them are in the tracking and focus servos, and one is the laser
power pot as I recall ) a few degrees from their original set positions,
should not be anything to worry about

Arfa
 
Good, so I can put my mind at ease... lol

I forgot to mention in the original post of mine, the first CD I
tried, the one that spun backwards, was a printed music CD (real
CD).. And the game CD that froze at a certain audio track was a CD-
R..

being the CD-R game was super sensitive, im wanting to give it the
benefit of the doubt it was because it was a CD-R, though I used a
special type of "mastering" CD-R, ones the music industry use, and
would think the KSS240a would atleast have no problem with those...
 
A

Arfa Daily

Good, so I can put my mind at ease... lol

I forgot to mention in the original post of mine, the first CD I
tried, the one that spun backwards, was a printed music CD (real
CD).. And the game CD that froze at a certain audio track was a CD-
R..

being the CD-R game was super sensitive, im wanting to give it the
benefit of the doubt it was because it was a CD-R, though I used a
special type of "mastering" CD-R, ones the music industry use, and
would think the KSS240a would atleast have no problem with those...

A burnt CD is nothing like as reflective as a pressed CD, so any laser
low-output issues, will be exacerbated with a home burn over a commercial
pressing. Actually, '240s are particularly bad for not liking anything other
than genuine pressed discs, and need to be in really good condition to play
them successfully

Arfa
 
A burnt CD is nothing like as reflective as a pressed CD, so any laser
low-output issues, will be exacerbated with a home burn over a commercial
pressing. Actually, '240s are particularly bad for not liking anything other
than genuine pressed discs, and need to be in really good condition to play
them successfully

Arfa

Ok. What compatible replacement laser assmebly do you reccomend?
Being it's in a tray loading Sega CD, does it have to be an EXACT
match? (will the Sega CD even know if the drive is changed?) Also,
what replacement will accept a CD-R, the best?
 
A

Arfa Daily

Ok. What compatible replacement laser assmebly do you reccomend?
Being it's in a tray loading Sega CD, does it have to be an EXACT
match? (will the Sega CD even know if the drive is changed?) Also,
what replacement will accept a CD-R, the best?
It has to be replaced with a KSS240A, and I would recommend a genuine Sony
one, if you can find a supplier. Do not use one of the subs such as the
NKS240A. I have never had much luck with them. If you find a website selling
lasers, you will often find two prices quoted. The cheaper one is usually
for a second-source replacement, and the slightly more expensive price is
for a genuine Sony original, which may be actually declared as such. I would
recommend going for the Sony original in the case of a KSS240, as they are
fussy lasers at the best of times. For products which use the KSS213B or
KSS213C, cheap second source replacements are usually fine. For KSS213D, E,
or F, again I tend to use genuine originals. If your unit is going to be
working a lot with home-burn discs, I would definitely go for a genuine Sony
replacement. No alignment should be necessary after replacement. As you say,
it shouldn't even 'know' that the laser has been replaced. There is not even
a shorting blob to remove on a '240. You can just drop the new one right in.
I would however recommend that you wear a wrist strap connected to an anti
static mat to do the job on, as laser diodes are quite sensitive to static
discharge, when their connections are open, as they are on the '240 until
it's plugged in.

Arfa
 
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