I have a SC-88Pro in which the RCA outputs on the back work fine, but audio from the front headphone jack has a constant loud electric hum in the background. It starts as soon as the unit is powered on. Ideas on how to repair this?

I also did the input voltage mod (the unit was from Japan originally and I am in Europe) and changed the mains cord so the plug will fit in a local wall socket, but right now I have the leads from the new power cord just directly soldered on to the power switch board. The original power cord on the other hand had these things on the leads:

Is it possible to remove them and attach them to the new cord somehow, or can I buy new ones somewhere? It seems to me the outer layer might be heat shrink tubing and the things inside are supposed to be attached to the wire by pressure, so probably not reusable easily. I'm not sure what these are even called since I am not very experienced in working with electronics.

(note that the noise problem was there when I tried the unit with a stepdown converter before I even opened it, so that one is definitely not my fault)