Really noisy Aux Sends

[RandyRhoads1981]

The 4 Aux Sends on my M-520 are super noisy, especially Aux 3/4.
I mean REALLY noisy, I don't think it is normal noisiness.
It has a ton of hiss. No popping or crackles.
I have cleaned the Faders before with Deoxit G5.
Could the problem be from bad Capacitors?

 

[Blue Jinn]

I have a 520. A few random thoughts:

switch teh meters to external to take out of path,

how are you bringing the aux back in (is the noise on teh send or on the return path?) maybe try using the aux with your headphone amp e.g. and see if noise is there.

how are the levels? there are the level knobs on the channels and then the summing faders, are all of those optimal?

I'm not in front of my board at the moment so these suggestions are off the top of the head.