[zenithfan1]

If the hum is present when the volume is all the way down and/or there is a slow crawling slight bend in the picture, that is a sure sign that the filter caps are bad. I would highly recommend replacing them no matter what it is doing, they are way past their expected lifetime. A dead short in one can blow the power transformer. These caps can also explode. I restored a '65 Zenith roundie that had one explode, it took over 6 hours to remove all the black goo off of everything. Luckily, the transformer and other parts were not damaged.