I got two of these, one is a TD-7 and one is a TD-8. They seem to respond to input but do not make sound. The little "trigger" light lights up.

I also have one of another brand that only puts out sound through the headphone jack.

I am comoing up with a blank finding prints fro these. Anyone know any common failure oes or whatever, or worked on a bunch of them ? Need a couple of tips.