McIntosh MX121 Test Tones?

I have a MX121 but plan on changing to a MX123 soon. My theater is being rebuilt in a new home. I would test the cables. You state that there is a signal; however, have you tested the outputs of the amp powering the center channel? Swap amps and run the center signal to the swapped amp. Also test the center channel speaker with another amp that has a good signal and is outputting a signal that is either left, right, rear, or anything not center. This will help to let you know the center speaker is functioning. This would be my first test and then swap amps to the center and or cables from the pre out on the MX121 with another set. 
 

If the source on the MX121 is HDMI and not all analog, you may want to check the settings to see if you need to change to analog outs for the audio out related to the source feed. I purchased a 5.1 HDMI splitter that allowed me to use RCA analog outs. This may allow you to convert the source signal (blu ray, DVD, etc.)  to analog  which then can be plugged into the analog in on the MX121. This will only work for one source unless you get a rocket fish HDMI source selector. This will allow you choose up to 4 sources and then run the audio to the MX121. The HDMI splitter has a HDMI pass through which enables the video signal to be passed to the MX121 source inputs. I always used media player as my default source. Don’t forgot to check audio signal setting such as PCM, pure direct, stereo, etc. for the selected source on the MX121. 

I purposely left this out of the OP because I thought that it would only muddy the water, but the MX121 in question is not actually here. It used to belong to me, but now it belongs to my younger brother ... the point being that I’ll have to guide him through this remotely.

@dinov - I don’t mean to sound like some sort of audio snob here, but the audio system in question is very expensive, so a dedicated HDMI monitor is a permanent fixture in the setup. As the prior owner of this MX121, I have a hard copy of the manual.

@dodgeshackleyrips - As mentioned in my response to user dinov, an HDMI monitor was part of the system from the start. It reads like you’ve employed test tones via the MX121 in the past. I’m also gleaning that said "test tones" are found somewhere in the Speaker Configuration video menu. Is that correct?

As I mentioned in my second post, I remember enough about the MX121’s video menu system to know that it’s pretty complex. I’m just hoping to get some pointers from someone who presently owns an MX121 before I try guiding my brother through this remotely.

70’s mac- there is a location in the mx121 speaker set up menu for level matching each speaker. That will provide a test tone that toggle through each speaker. It is MUCH easier to attach an hdmi cable to a tv or monitor during this proc to provide a display rather than navigating the front panel. Good luck!

There should be a button that changes the input of the MX121 on the tv, then you can access the test tones etc there to do your set up. I have an MX120 and there’s a button on the face that says a setup. You have to connect the HDMI to the tv properly. Download the manual if you don’t have it. 

I was thinking the same thing, so I went through the Oppo's speaker configuration menu yesterday and all six channels (including the subwoofer) are ON. 

It's been a long while since I dived into the MX121's menu system, but I recall enough to know that it's pretty in depth.  This is why I was hoping to find another MX121 owner who's gone down the test tone path before.

Thank you for the post.

Is it possible the OPPO is not putting out it's center info?   I have a 103 and it's been a while since I used it in surround but if I remember correctly it also has test tones built in.  The center may be turned off in the oppo or 121.     

If you go into the Mac's menu it should be able to send a tone to every channel.  It should identify center as it sweeps from L to C , then R and so on.   

If you get a tone through the Mac center then most likely a cable or center is off in the player