Famicom av control port doesn't work

[sdekaar]

(first sorry for my poor english )

hi i have some problem with my famicom av
with the controller on port 1
only the button A works and for the consol A=start
the controller is ok, it works on my second famicom av and my nes pal.
in my opinion some Capacitor or chip are dead on the motherboard.

there a lot specialist here so i demand your help for fix it