Hello, I'm quite new to this and have bought a Rotel RP1033. It was sold with a shake at 33, which I fixed (weighting issue), but the phono plugs were disconnected, wires loose at the pre amp end of the cables. I used my basic knowledge to solder a replacement phono cable but there is now a buzzing in the left channel. Speaker produces the record sound, but with a background hum. I know thia could probably be many things, but is there any advice on things Inshould check?