Fixed! My player is now switching between AC/DC mode. I found an "A6" diode on a Diamond Multimedia Supra Express 56i ISA modem. I'm glad I didn't chuck it when I switched to an all PCI MB. I'm attaching a picture of the component for those that would like to see what it looks like.

I hope this info will help you fix your player.

In DC mode, I was measuring 2.53V on pin 1 of the diode when it should be 0.5V