My eaton 5110 was activated when our local power went down. Now, when turning it back on it beeps constantly, every 1/2 second, even with nothing plugged into it.

take the batteries out and have them checked and then go from there

I believe you will find that your battery is either dead or shorted.

Replace the batteries. A lot of the smaller UPS systems won't start or restart if the batteries are bad.

I recommend that you call Eaton (the manufacturer) service line: 800.356.5737. Here is the product page for the 3105: http://powerquality.eaton.com/Products-services/Backup-Power-UPS/3105.aspx?cx=3 You can also send an email:[email protected]

You probably need to replace the battery. Here is the product page link: http://powerquality.eaton.com/Products-services/Backup-Power-UPS/5110.aspx?cx=3 There's a PDF for the manual.

Sounds like the motherboard. Do you get any Beep codes?

Turn the power off on the switch on the back, and then back on again. Hold down the power button, keep on holding it down after the first beep, but let go once another couple of beeps sound. It should then take at max a minute but then it should show a screen set up section.

check whether the battery is functioning using a digital meter. If yes one of the Fets is not functioning.

According to symptoms we can consider two things:-
1) Problem with SMPS power supply
2) Problem with Motherboard display IC

1) SMPS problem -
As per your sayying, you had replaced the powersupply and tested it.
If new power supply SMPS is perfect then there may not be any issue with this thing
So to workout on it i would suggest that to Remove RAM from your system + remove CMOS 3V battery and restart your system.
So due to absence of RAM system will give 3 small beep sounds and take a pause (If internal speaker is connected then only you will be able te hear beep)

This signifies that your motherboard is working super fine
If you are not able to hear any beep sound even though you have connected internal speaker then there must be issue with motherboard

Thanks, and sorry for the extremely long message. :-)

Question- the beeping, is it short (1 second beeps) or long (2 or more seconds) and how many before it stops? or doesn't it? does it have any rhythm? The beeps correlate to some hardware problem, if you want to check the beeps yourself, just google "Bios beeps" and it will bring up a table of what the beeps mean.
J