How to Get Apc Back Up 750 Stop Beeping Mac

I wanted to take a recently repaired APC Back-UPS ES 500 Battery backup (I replaced the battery) and have it provide backup power to my AT&T U-Verse modem and wireless access point. The problem is, I have small children whose rooms are right above this room. When the power goes out (or the batteries go bad), these APC's let off an obnoxious piezo-electric beep-beep-beep, which is not cool to your wife when it wakes up the napping kids!!! I've read that you can disable the alarm with the windows software but I've not had any luck linking it up with an APC and I'm a Mac user anyway so I just wanted to permanently disable the alarm. Here's how you do it:

How to Permanently Disable the Beeping Alarm on an APC Back-UPS ES 500 Battery Backup

Tools Needed:

Hardware:

Step 1: Unplug the APC.

You don't want to get shocked.

Step 2: Flip the APC over and remove the battery.

I have detailed the steps to swap out the battery on the post below:

How to Replace the Battery in a APC Back-UPS ES 500 Battery Backup

Step 3: Remove the 5 phillips-head screws from the case.

They are located deep in the holes as follows:

Five Case Screw Locations

Step 4: Separate the halves of the case.

Be careful not to lose a screw as they will fall out and hide if you're not careful. You will need to feed the positive and negative cables through the slot they feed through the lower case. The circuitboard may come out of its slot and there are a couple other cables that may become disconnected as you separate the halves, but don't worry about that–I tell you how to re-assemble it later.

Separating the case halves

Step 5: Feed the battery cables completely through their slot and remove the lower case.

The picture below shows you what you'll see if everything stays in place (which wasn't the case for me). I actually took the picture below when I was re-assembling it because I forgot to take a picture when I was disassembling it.

Lower case removed and all the internal components in their place

The transformer will be loose, the power plug grommet will come out of the case, the reset button will come out, and the circuitboard will come loose too, and this is what it probably will look when you get yours apart (note that the circuitboard came up and out of its slot and the transformer is sitting on the desk out of the case, and a couple wire connectors came off too):

Add caption

Step 6: Locate the alarm buzzer.

Mine was almost in the middle of the board and was labeled BZ1:

Buzzer Location overview

Zoomed-in buzzer location

I considered putting a piece of tape over the hole in the top of the buzzer but when I placed my finger over the hole I still could hear the buzzer quite a bit so I felt like I needed to do something more extreme. I considered lowering the volume by putting a resister across the buzzer and tried 10K Ohm and 1K Ohm resisters, but that still didn't lower the voltage any noticeable amount:

Resister in parallel with buzzer

The buzzer must have a much lower resistance than 1K so that is why it didn't make any difference to have the resister installed. My single digit-sized resisters are huge and high powered (and there's not enough room on the back side of the board and I didn't want to waste a $4 resister) so I opted to take it to the next level…

Step 7: Remove the Buzzer.

I took some solder braid and removed the solder from the back of the board. I then grabbed the buzzer on one side and pulled gently on it while I heated each leg individually and popped out the buzzer. With my light behind the board you can see the round silhouette of the buzzer through the board:

Solder point locations for buzzer–note you can see the silhouette of the round buzzer through the back-lit circuit board

Here's what it looked like when I got it out:

The removed buzzer

No more buzzer:

The buzzer is long gone

Step 8: Reassemble your completely-quiet APC.

The first step for me was connecting the white and black wires under where the circuitboard sits. Note that the color of the wire is imprinted on the plastic behind the connectors:

Black and white wire connector locations under the circuitboard

Step 9: Reinstall the power button (if necessary).

Mine came off so I snapped it back on the push switch:

The power button put back on its switch

Step 10: Guide the circuitboard back into place.

Watch to make sure the power button goes in its hole. There is a slot on either side of the case, which holds the circuit board in place:

Circuit board slot on one side of the case

Step 11: Make sure the transformer is in its place.

There is a square spot in the case for it to set:

Transformer in its spot

Step 12: Re-seat the power cord grommet.

It is round on the side that goes in first:

Power Cord grommet in place

Step 13: Re-seat the reset button (if necessary).

It has a place moulded into the case to hold it in place.

Reset Button back in place

Step 14: Run the wires back down in their channel in the case.

There is a groove in the case designed to run them through:

Wires down in their channel

Step 15: Feed the battery cables through their slot in the lower case.

Feeding the battery cables back through their hole in the case

Step 16: Re-seat the lower case and reinstall the screws.

I actually installed the battery at this point, before reinstalling the screws just to make sure it was working correctly. Be careful that the battery connections are tight. When I replaced the battery in my other post I took a pliers and squeezed the connecter closed a bit so that it made a good connection.

Reinstalling the lower case screws

Step 17: Reinstall the battery.

Step 18: Reinstall the battery cover and battery cover screw.

Step 19: Plug in and press the power button (it may be on already though).

The LED is green when it is on and working correctly. Now you have a completely silent APC. You will need to monitor the led light because it now will be your only physical indicator that the APC is running correctly (aside from any software monitoring you may have installed):

Power LED light is green–you are back in business (and completely quiet)

All my APC Battery Backup Posts:

How to Replace the Battery in a APC Back-UPS ES 500 Battery Backup
How to Replace the Batteries in a APC Smart-UPS 1000
How to Replace the Battery in an APC Smart-UPS 1500
How to Permanently Disable the Beeping Alarm on an APC Back-UPS ES 500 Battery Backup

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