A reader has contributed some scans of the Sony MDX-C150 service
manual and comments about adjustments he made to his unit.
Service Manual Sections
With recordable (MO) discs, MD unit was skipping when cold but would
play when warm/hot. Premastered MDs did not exhibit problems.
After reading the manual I found that there are only two adjustments
that are different for MO and premastered MDs: the focus and tracking.
Looking at the circuit board diagram, I located the variable resistor
for adjusting the MO focus bias. I put in an MD and put the player in
test mode (which runs the laser continuously, as opposed to the
normal, intermittent laser activity) and started playback. The MD was
skipping badly, like a scratched CD. With a jeweler's screwdriver I
then tweaked the resistor. I adjusted the focus bias until playback
became clear, and that did it.
One note though, I have some Maxell disks (the new clear kind with
powder blue lettering on the shutter) that still skip no matter what
I do. All the Sony (even the old grey ones), TDK and some older Maxell
(smoked plastic ones) all play fine. So there are some differences in
the disks as well.
And cleaning the lens doesn't seem to help. Regarding the MD lens
cleaner, been there done that.