Distinctive audio buzzing high and low problem

[ketron281989]

Hi guys, I bought a Philco 50T-1402 a while back, pictures are in my gallary, this set was fully restored from the tv collector I bought it from. There is a real annoying buzzing that changes tones when a commercial comes on, or sometimes they just change for no reason, I think something is wrong, this weekend or next I am going to take out the chassis for the first time since purchase last month to examine. Could any of you help Identify what this noise could be, I don't think it is interference as my computer is fully shut off, I do run it off a variac, have a converter box and digital cable box hooked up, but they are about 3 or 4 feet away from the set, there is nothing else around that could provide electrical interference.

Do any of you know a simple fix or cause, or have any of you experienced this type of problem. I will work on getting pictures here soon, but for the time being any help would be appreciated.

Thanks guys
Jon