The manual does not indicate any speaker on the MoBo.
See page 2-37, System warning speaker: "This 4-pin connector is for the chassis-mounted system warning speaker. The speaker allows you to hear beeps and warnings."
Oh, I see that connector - mistook as being the 10 pin job, which is actually on the other side of the MoBo. Should have counted. The speaker must be hidden up by the audio in & outs in the top-front (or maybe it’s really the front-top.)
In any event, it ain’t-a-beepin.
Will check PS voltages after supper. :-)