Nes and Famicom hardware problems

[misjah]

Hi all. I have a nes that is working but the only problem is that the picture is yellow-ish (both RF and Composite). What can cause this problem?
I also have a noac with no sound. It was working good but after some time the sound just stopped. I know there are not much parts to fix but maybe there`s some tip what to check out.
No loose wires or something like that.