I need a remote code for a ATT uverse remote to control the volume on the Yamaha RX V520 system

The RC-866M is the remote. What you need to do is add the codes for your Onkyo receiver into the ATT remote. There are 4 or 5 different Uverse remotes, but most can be reprogrammed by pressing the 'Menu' and 'OK' button together. First add your Onkyo codes to the ATT remote as an 'aux' device. After that is working, you can control the power and volume by adding the 'aux' device (Onkyo) to the power and volume buttons on the uverse remote.

These are all the different Onkyo Receiver codes:
Onkyo: 5002, 5018, 5073, 5074, 5075, 5076, 5077, 5078, 5079, 5080, 5081, 5082, 5084, 5085, 5086, 5087, 5130, 5131, 5140

This is how to reprogram the S10 style of Uverse remote:

http://www.att.com/support_media/images/pdf/uverse/standard_black_remote_control_uverse.pdf

I had the same problem with my U-verse s10-10 remote and a yamaha SR 300 soundbar. Here is how I got my volume control (but NOT power control) on the yamaha working:


First - always send volume control to the AUX button:
Press and hold AT&T key and OK for 1 second, release, look for 2 flashes.
Now press AUX button. The AUX button will show a long flash.

Second - Go through the manual programing steps listed in the guide for the AUX button (hold AUX and OK for 1 second, release; 2 flashes, punch in code). But instead of pressing the Power button to try to turn off your yamaha soundbar, press the volume up / down and Mute button. I think the code that worked for me was 4045 but I honestly don't remember.

The key is that you have to send the volume control to the AUX button first or it's all a wash.

ATT Uverse remote doesn't work well with Emerson TVs.
Most will turn off with the correct code but NOT ON.
Find the code that will turn OFF the Emerson TV.(volume should work too)
When you want to want to turn ON your Emerson TV Try This (Believe it or not)
Wave ATT Remote slowly and press ON in mid wave. The ATT remote on frequency must be slightly off. This works every time for me now that I know the secret. Remember Doppler Effect from High School Physics.

I used 5120 to turn off and on the receiver on the Aux button, I am also control the volume on the recevied by assigning the volume control using 955 code. The one thing I lack is a way to change the receiver input between BD, HDMI1, HDMI2, etc. I still have to go to the Receiver remote for that. I know the Uverse Receiver can't do everything, but if I could just get the input to change on the UVerse Remote, it would be awesome. I'm trying to avoid getting a Harmony. The blu-ray and tv also work, which is great! See this reference for the silver remote:
http://www.att.com/support_media/images/pdf/uverse/remote_control_user_guide.pdf
If you have black, you may need to visit the AT&T support site to get the black manual.

Click Here for the list of Manufacturer's Code for AT&T Uverse

You need to try other codes for Yamaha, as clearly the one you have put in the remote is incorrect, perhaps it was for an earlier model.

Hi,
Maybe too late for you but ATT just gave me a code that works with my Vizio plasma. Code is 1343. Even the mute works correctly. They gave me some others to try but I didn't need them. Other codes were 1018, 0030 and 0056.

Do an automatic search for your code.

1. Turn on the device you wish to program
2. Point the remote control at the device
3. Press and hold the mode key (i.e. tv, dvd or aux) you want to program
4. Without releasing the selected mode key, press and hold the OK key simultaneously
5. Release both the mode key and the OK key -All the modes keys will flash twice indicating programming mode
6. Enter 922 by pressing the number keys on the remote control -The selected mode key will flash twice indicating correct entry (for anything other than AUX go to step 7, for the AUX mode searching only, press and release the play key then press 1 for VCR 2 for Receiver/Tuner 3 for Amplifier or 4 for Home Theater In The Box (HTIB) - The AUX mode keys will flash twice indicating correct entry)
7. Press and release the PLAY key, every time you do this, autoserach will try a different code, continue to do this until your device turns off. (if you weren't paying attention and you miss it, the REW key can be used to go back through the codes one at a time, and the ff key can be utilized to move forward through the codes one at a time.)
   
8. To save the code press the ENTER key (below the number 9) then press the exit to return to normal operations. (the selected mode key should flash three times
9. Turn you device on by selecting the appropriate mode and power.
   

(I have the RX-V659). Because the Yamaha remote has TWO SEPARATE buttons - power ON and power OFF (standby). This problem can't be fixed. There's a code to choose power ON and another code for power OFF. But one button can't be two buttons. Bad engineering\ design by Yamaha in my opinion

Yamaha Receiver/Amplifier 5003, 5014, 5015, 5021, 5102, 5103, 5104, 5105, 5106, 5118, 5135you can use those codes