I JUST received the Tascam DR 100 and after doing a few audio recordings I cannot hear anything from the speaker. Headphones work just fine.
The speaker switch is turned to ON, I do not have headphone plugged in, and the playback level is set to an average level.
I've read you have to be in "playback mode". I'm assuming playing mode is just when you are not recording? You can play from the home screen just fine with headphones plugged in, but nothing comes from the built in speaker.