No Sound Output Powerbook G4

Powerbook G4 1.67 V.10.5.8 2GB w/hi-res screen upgrade.

This thread's been discussed before with lots of comments but I'm not helped yet. So here goes: Before I shut the Powerbook down the other day I had output sound from the internal speakers. And plenty of battery power. A day later I powered up, but didn't hear a startup chime. Then discovered, while playing a Youtube video, there was no sound whatsoever. In preferences, under Sound (and highlighting Internal speakers), it says; The selected device has no output control. Indeed, none of the volume controls (on the keyboard, or menu bar) are functioning. I've never used headphones or external speakers with this Powerbook, nor do I have any. It just seems odd that a sudden sound failure would occur when it was working fine the day before, and the laptop wasn't moved from the desk or jostled or moved at all. I'm not a techie and I don't really want to try a paper clip solution as I've read. But I'd like to know if there is a probable or easy solution before taking it to a repair facility. Could it be a sound card failure, a hardware failure, or some common fixable glitch? Thanks.

First thing I'd do is reset the PRAM. Power off the system. Power back on and hold down the Command-Option-P and R keys, and see if the system will give you a startup chime. If not, your sound board (Left I/O board) is hosed. If you can get a startup chime, but still no sound internally, try launching GarageBand and see if it will reset your sound drivers.

Resetting the PRam worked! Got sound again. Thank You!!!!!

Funny though, I set the Powerbook aside unplugged (with full battery power) for less than 24 hours, but when I started it up again the sound was off. So I reset the PRam again, but still the sound was off. So I reset the PRam again, and the sound is back! Very strange. Any thoughts on this? Thanks.