If the power light doesn't come on, that's pretty basic! Since you have a red light, you're getting power, I'd say the power LED is in backwards.
Top suspect is the output amplifier having shorts between the pins. They are VERY close, and it's very easy to short them without knowing it happened. Use an ohmmeter to check between adjacent pins and make sure none are shorted.
As far as the signal, lots of stuff could have affected the signal. Do you have anything like a 'scope to look at what's happening in the circuit?
