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?