Re: Sony laser questions

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...

On Mar 21, 5:27 am, "Arfa Daily" <arfa.da...@xxxxxxxxxxxx> wrote:
<blackevilweredra...@xxxxxxxxx> wrote in message

news:1174456673.587122.99870@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx



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


.

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