Sega-Naomi

I have an old Naomi motherboard (which I have now replaced!) which works fine but the sound is very quiet and there is a loud humming noise... I think this is a consequence of plugging 2 cables in incorrectly on my Naomi Uni... I believe it was a monitor lead to a speaker lead which caused this... I'm guessing something blew?



Is there any fixes/solutions for this that won't cost the earth?



Cheers guys