No sound from speakers in TI 667MHz

I got a powerbook g4 Titanium 667MHz DVI from a friend. It has had a hard life so far the right hinge is broke, peeling paint, but it does  work except for I get no audio from the speakers but If I connect headphones up it does work. Any ideas on how to track down the problem

Hi there. This year I have bought PowerMac G4/400 (Gigabit). It has 896Mb RAM, there is a USB 2.0 PCI controller, and recently I've installed SerialATA PCI controller and 1 Tb SATA hard drive.
Mac OS X Server 10.4.11 performs great on this hardware. You can access website hosted on this great computer at http://victor3d.karelia.ru/ .