I have found several brands of EF86 tubes are very sensitive to RF noise. Make sure its not any of the tubes by moving your hand close to them,(do not touch them) if the noise level changes then try another tube.
If you have a Tube Cage, try taking it off or if your not using it putting it on.
You dont say if your using any power conditioning, if you are, try lifting the ground on the amp by using a cheater plug. This might indicate a ground loop.
Try a better power cord on your amp. Perhaps one with better shielding.
I have used the Blue Circle Noise Hound with EXCELLENT results. Just plug it in to any outlet close to the outlets that you use for your tv.
If you have a Tube Cage, try taking it off or if your not using it putting it on.
You dont say if your using any power conditioning, if you are, try lifting the ground on the amp by using a cheater plug. This might indicate a ground loop.
Try a better power cord on your amp. Perhaps one with better shielding.
I have used the Blue Circle Noise Hound with EXCELLENT results. Just plug it in to any outlet close to the outlets that you use for your tv.