Magnavox IP-3751

I have a Magnavox IP-3751 (that is the pt number on the back of the console) that used to belong to my grandparents.
It sounds great except that there is a loud hum that comes and goes even when the volume is turned to 0.
I've read a few posts to see if this is a common issue and if i can fix myself. I will see if it is something as easy as bad connections or reversing the polarity of the a/c plug. I looked around the internet and this forum but have not found this model listed. Does anyone know what year this unit was made.
I'll add pics later.

That type problem usually indicates a power filter cap problem--advise you not to operate it till problem is resolved, as further damage could result-- Ron Rich

Do you know how much that would cost to fix? Rough estimate.