Sherwood s-9400 static with volume knob

I have a Sherwin s9400 that I inherited from my father on the outside it looks in mint condition how when I plug my speakers in and I move the volume one speaker will cut out or the other will cut out and there's a very loud static.  The sound is so much better though when I do get it to play then my newer amp so I really would like to use it but can't as it's currently basically unusable.  I've seen YouTube videos about spraying contact cleaner into the knobs on the inside but I don't see any screws on how to take the outside cover off does anybody know how to take the cover off?