I did try changing some BIOS settings, I wanted to identify the source before trying everything else. We have not ruled out the PSU.
Yes USB connectors on the motherboard as well as on the front of the case were tried. I know both Bobnova and Oklahoma Wolf, that is an excellent idea.
It's possible that it's the PSU, but fairly unlikely. PSUs are decently shielded against outside radio, and the load that a mouse transceiver puts on it is laughably small.
If you have another PSU I'd test that, doesn't have to be fully installed in the case, just plugged into enough of the bits to get to windows.
Have you put an ear to the transceiver/dongle itself?
I would tend to guess that it's something that doesn't appreciate the ~2.4GHz radio being stuffed into it, but the possibilities on that one are endless.
Do you have another GPU you could stuff in? I'm suspicious of that one for reasons I can't explain.
I will insert another video card tonight and eliminate that as the suspect. Next I will take out every other card in there which would then leave us with motherboard itself or the PSU as the last remaining suspects.
An interesting development. The PSU in my case is the Corsair TX750, Model: 75-001309
Its fan does not spin unless the temperature is detected to be [not sure exact number] degrees. Get this: when stopped, its large fan reacts to mouse movements ever so slightly, but only when the noise is audible. You hear the high tone but low volume pitch. The fan definitely reacts to mouse movements, not the physical movement of the desk.
Exactly as I was looking at it, the temperature reached the critical point and activated the PSU fan, it started to spin and the pitch was gone!
Obviously I need to replicate this reliably. My plan is to wait until the noise is prominent, then hit the system with Prime95 load which will make the fan spin. Then if the noise stops - we can be sure we have the culprit?
The additional thing here is this: fan not spinning does not automatically mean the pitch noise is present. When there is no pitch noise - there is no fan reaction even if it is not spinning.
But when there is noise - then the stopped fan actually physically jerks slightly - it reacts to mouse movement and the pitch is audible.
I have to make triple sure through testing that everything I just said can be replicated, and using Prime95, I think I know how to replicate it. So we'll see. I was already looking for new video cards, but that wasn't it!
Aha! Sounds like the thermistor circuit is picking up the radio from the mouse. That is an angle that hadn't occurred to me.
It has to be on the edge of spinning, and the mouse puts it over just slightly causing the motor to fire briefly.
EMI is fascinating stuff.
If this is the case, Corsair (well, whoever built the unit for them) didn't put enough of a filter and/or hysteresis on the fan control temp sensor circuit.
Is the PSU in the case fan up or fan down? Or more specifically, does the fan point in the general direction of the motherboard and/or mouse and/or mouse USB dongle?
The speaker is not required. Other people had problems with noise from speakers. This issue is not about noise coming from a speaker.
It was coming from inside the case. I believe we have it narrowed down to the power supply's fan control temperature sensor circuit, which is picking up wireless mouse signals. It looks like that whoever did the job for Corsair for these in 2012, did a lower quality job than going back as far a 2008 when identical Corsair models did not have this problem.
When I called Corsair 3 weeks or so ago, the Corsair guy told me he had exact same problem and a new PSU did not fix it for him an d that he doesn't know what the source was.
And yes he also talked about how my PSU is only supposed to spin when under load and he also mentioned Prime95 himself to force the fan to spin because Prime95 would put he PSU under enough load to make the fans spin.
But yeah, the fans do not spin when there is no load on this model...
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