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Continuous alarm on ES-350, power light (green) blinking. There are no other audio/visual indicators. Circuit breaker button is popped out, won't reset, attached devices have power. Power cycle and alarm resumes. What's the problem?

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Make sure you are not plugged into a switched duplex and someone turned the "light switch" off like we did. Simple fix (LOL)

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Have you recently added anything to the chain of devices plugged in? You said the breaker keeps popping. A dead battery is the most likely cause, but I find it odd that it can't even reset the breaker. How much do you have plugged into the battery backup socket vs the pass-through socket?

Is that the overload alarm? Unplug most devices and just start with a couple basic ones and see if the situation changes at all.

Battery Replacement might be your only option. I would weigh your options though. Some of those batteries can cost as much as a new unit. Especially with the small models like the one you own. Every small UPS I have owned has just been replaced with an entire new unit, on sale of course. ;)

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Hmm. Nothing has been added in quite some time. I'll look into replacing the battery. Thanks a lot for your suggestions. – alan Nov 17 '09 at 18:46
+1 "overload continuous tone alarm" mentioned on… – Kez Feb 25 '10 at 20:22

Not so. This seems to be a common problem, and buying a $35 battery for a $50 unit will make you very angry when it still doesnt work. These should be recalled. According to APC, there is a 2-year warranty on this item. I dont know how picky they are with warranty cards as most people never register them.

The transformer inside is an autotransformer. It is usually NOT the battery, as the reviews of the $34.99 replacement battery on the APC site have lots of people complaining. There is a 40 amp fuse soldered on the control board. Mine wasnt blown, neither was my breaker tripped. Bench testing the transformer showed no output (should be 12 to possibly 16 volts, one lead runs to the + battery and the - battery connects to the board. The power charging the battery has to be rectified (made DC). There is another transformer on the board which is marked on the PCB "40A/32v" so its run through diodes or a half-wave rectifier and is probably the 16-volt charge to the battery I'd mentioned. I just took mine apart, I see no burning of any components, no smell, just that darned alarm. Only looked at it for an hour so far. There are free schematics on but for the 250, 400 and 600...still looks the same.

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The only time I have seen the continuous alarm was when the battery is dying - maybe it is time for a replacement... failing that, check that it is plugged in.

How long have you had it for? Could just be reaching the end of its life.

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That was my first thought, but indications don't match what documentation says accompanies bad battery (red Replace Battery LED) - but wouldn't be the first time I've read an imprecise document. Consensus here is that's around 18 months old. There's only the one LED, so I'm assuming that it shares Power and Replace Battery functions - right? – alan Nov 17 '09 at 18:13

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