How I Fixed the Beeping Problem of My 'APC Back-UPS ES 700'
Lately, my APC Back-UPS ES 700 was crippled by the problem that seems to kill most of its models: after a surge event, instead of switching to battery, it started to continuously beep. For a while, I could restart it several times and the problem would go away, but in the past few days, nothing would make it turn on again without constant beeping.
First of all, I wanted to make sure that the beeping is not caused by a normal condition. I checked the user manual's Status Indicators section for Constant tone audible indication.
It was not a normal condition, so it was time to take it apart.
Before opening it up, I unplugged it from the 220V outlet, disconnected the battery and left it sitting for about an hour for any caps to have a chance to discharge.
Once opened, I took a picture of its connections, as there are plenty of them and I wanted to remember how to put it back.
After a quick visual inspection of the main board, it was clear that no parts were blown. Next, I checked on a hint from a YouTube comment, that someone was successful in fixing it by replacing some bad capacitors, but he/she didn't go into any more detail than that.
Time to take out the ESR Meter. This will allow me to determine if a capacitor might be bad without taking it out of the circuit.
Measured all capacitors and sure enough, found 4 caps that were dead as a dodo. I've circled them in red in the following picture.
The fix was pretty obvious by now: I needed to replace the bad caps with good ones.
All 4 bad caps were the same: capacitance
22uF and voltage rating of
25V made by Jamicon.
I replaced them with better-quality Nichicon capacitors as I didn't want to replace them again anytime soon.
I also made sure to put them back in the same orientation, as these electrolytic capacitors are polarized. The polarity of the caps is indicated by a solid line on the side with the negative lead.
After putting it back together I realized that this also fixed another problem: for as far as I can remember, like 5 seconds after starting the UPS, it started buzzing loudly for a while. Now I can barely hear the buzzing.