8PT Hum bar

[Cory]

Hey guys, I've got a slight problem I thought someone might have a clue to. I just finished recapping one of those RCA 8" 8PT metal sets and have a great picture and sound. Works great. Except, I detect a very slight hum bar that rolls upwards, maybe an inch or two in width. Playing with the fine tuning I can invert the bar with respect to the picture (it's a very very light bar, most noticeable on a dark picture). I can _almost_ tune it away. Tuner tube shields are in place.

Any ideas?
TIA, Cory