Sound disappeared on Dell Inspirion 8100

[Michael R. Wayne]

I had 4.5 installed on my Dell Inspirion 8100 and sound worked OK.
Then, I upgraded to 4.7 and the machine acted like sound was muted.
I just upgraded to 4.8 and there has been no change.

Sound works fine under Win2K so the hardware is OK.

The kernel sees the sound card:
   cat /dev/sndstat
   FreeBSD Audio Driver (newpcm)
   Installed devices:
   pcm0: <ESS Technology Maestro3> at io 0xdc00 irq 5 (4p/1r/0v channels duplex)

and I can run programs that use the sound card:
   mpg123 Heart-Barracuda.mp3
   High Performance MPEG 1.0/2.0/2.5 Audio Player for Layer 1, 2 and 3.
   Version 0.59r (1999/Jun/15). Written and copyrights by Michael Hipp.
   Uses code from various people. See 'README' for more!
   THIS SOFTWARE COMES WITH ABSOLUTELY NO WARRANTY! USE AT YOUR OWN RISK!

   Playing MPEG stream from Heart-Barracuda.mp3 ...
   MPEG 1.0 layer III, 128 kbit/s, 44100 Hz stereo

but nothing comes out the speakers.

It's as though a mute switch has been hit.  I tried toggling the mute
(ALT-End), hitting volume up (ALT-Page Up and the buttons near the 
power switch) with no efect.

I'm at a loss as to what to try next.  Any ideas?

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