3 ms·

> This isn't reproducible by removing the battery entirely, either. If you take it out, the clock loses all ability to function and just resets constantly. So h

> This isn't reproducible by removing the battery entirely, either. If you take it out, the clock loses all ability to function and just resets constantly. So having a mostly drained battery seems to be doing a little work so that it resets once but then resumes normal functioning (until the next time it tries to go off). I think what this really suggests is that the transformer and power supply are providing multiple voltages. The +9V rail is broken, but the other rail (maybe +5V) for the LED display is fine. So the alarm chip and the alarm sounder is running only from the 9V battery. If the battery is weak, then the sudden power demand from sounding the alarm is too much, the voltage dips and the chip resets.

05 2y ago
> I think what this really suggests is that the transformer and power supply are providing multiple voltages. The +9V rail is broken, but the other rail (maybe +5V) for the LED display is fine. There's a reference design in the LM8560N IC PDF that suggests that the additional secondary winding is only used to drive the display, and all other electronics is powered off the main rail. The 10V cap is kaput and it can't filter the input power, 9V just acts as a filter (even a discharged one). The OP should replace the cap with a 16V one, because a 10V cap on a 9V rail just isn't right..