I don't know what you mean when you say a "pile of signal noise", but the phono input is different dfrom all the other inputs on that machine.
It's made for use with a very, very low output magnetic phono cartridge which requires an additional stage of amplification and special equaization, which the phono input provides.
All other source devices output a much higher line level signal.
If you plug them into a phono input you are overdriving the bejeezus out of that poor, overloaded phono input.
Now, it's also possible it's broken, but the only to find out for sure is to plug a turntable with a magnetic cartridge into that input and see how it sounds.