The most likely thing is a broken wire/disconnected cable. If you recently worked on the machine, perhaps you didn't securely reconnect the speaker cable?
The fact that you get sound from the jack means that the amplifier is working. There isn't much between the jack and the speaker, so it reduces to very few possibilities: bad jack, bad wiring, bad speaker. I no longer recall if there is a large coupling capacitor along the way, but if there is, I believe that the jack is downstream of it. Given that the jack provides output, that would tend to absolve the capacitor (if there is one).
The speaker itself is easy to test. A standard ohmmeter will reveal continuity -- it should be a couple of dozen ohms. The exact value isn't critical. If it reads only one or two ohms, or infinity, then the speaker is bad. If it turns out to be the speaker, that would be the first one I'd ever heard of going bad in a compact Mac.
The fact that you get sound from the jack means that the amplifier is working. There isn't much between the jack and the speaker, so it reduces to very few possibilities: bad jack, bad wiring, bad speaker. I no longer recall if there is a large coupling capacitor along the way, but if there is, I believe that the jack is downstream of it. Given that the jack provides output, that would tend to absolve the capacitor (if there is one).
The speaker itself is easy to test. A standard ohmmeter will reveal continuity -- it should be a couple of dozen ohms. The exact value isn't critical. If it reads only one or two ohms, or infinity, then the speaker is bad. If it turns out to be the speaker, that would be the first one I'd ever heard of going bad in a compact Mac.