oh, and yes I had miss typed the model # - it was the 2427c....

Well it turns out that my problem was an old logitec headset that was plugged into the back of the tower. My speakers were plugged in to the "rear" speaker jack below the audio input/output jacks...

After the Win 10 upgrade, (running Firefox) Pandora, U tube, Quicktime, and Itunes audio all quit working....
this is what I have in the Manage Audio Devices control panel:

Speakers /...