Hum in Magnavox Astro Sonic

I bought a Magnavox Astro Sonic console stereo with am/fm and phono. The model # is 2st686. It dates from 1965. It is a huge thing,6 feet long and weighs a ton. It works good except it has a hum. The hum gets worse as you turn the bass down. It has 2 brown electrolitic caps above the power transformer. Would those be bad? I know filter caps are what usually cause hum. Also it has a control called timbre and one called squelch sens. What are those for? I have never had a stereo with those.
John.