A SOLUTION IS HERE! Same problem here. After alarm time is reached, lights goes off, display goes to maximum brightness. Disconnecting or performing the reset didn't help. As "professor" suggested, but was widely ignored, the problem turned out to be the speaker! (Although it was still working!) Easy to test: remove one screw at the bottom, disconnect the speaker by pulling the small connector. Now test the Alarm function. Light stays on at alarm time? Good! Now connect anothet speaker and test again! My 'defective' speake hat an Impedanz of only 3.2 Ohm. I replaced it with a 8 Ohm Speaker I had availabe. Now the HF3520 works like a Charme again. Good luck, wega