I have the same issue. Someone posted this:
One thing.. the power level or constant, piercing tone of the alert tone is blowing your little 1.5w coil based speakers. I thought my radio had died until I plugged headphones into it and found it was still doing its job. I figured it was an intermitting 1/8" jack bypass switch.. so I cleaned that out and resoldered it. No dice. Checked the 8ohm 1.5W speaker.. open.. hmm.. hooked up a headphone to the speaker terminals.. bingo. Bad speaker.
I replaced your design with a bit beefier 3w/8ohm 1.5" driver out of an old Rat Shack tape recorder. Works like a charm now.