Sony megastorage 300 cd changer
Hi
There are many things that can cause your problem, I can tell you the most likely ones, but I recommend you don't take the unit apart, as the mech. in a 300 disk changer is complicated & delicate, and you may just cost yourself alot more money than getting it repaired.
The symptoms you sescribe can be caused by failing laser pickup, dirty laser lense (especially if you've done home renvations with drywall), split drive gear that moves the laser on the sled rails, or even a hair or piece of dirt in the gear teeth of that same gear. The unit will play fine, until it hits the tooth where the debris are, then it skips, or jumps back a bit and starts again until it hits the same spot. Also..badly scratched or finger printed disks will cause that, but that is the first thing most people check.
I wish it was something you could repair yourself, but my best advise is to take it to a reputable repair shop, and hope it is not a bad laser, as that is a fairly expensive repair.
Hope this helps, Good Luck!