I recently picked up an old BTI LK 2000 amplifier. It was in sad shape and not working. After fixing the Power supply, Band switch and timing, New RFC plate choke and door knobs and chimney, The amp is producing legal limit power on 10 to 80 meters. The PS is a traditional Supply with Center tapped UTC plate transformer at 3.5 KV with 25MFD 4KV oil can. The only issue is a high pitched rattle/noise that I thought was the blower motor bearing. I oiled and rubber mounted the blower only to find the noise still present. I carefully used a stethoscope and found the noise is from the tube itself. I disabled the filament power and instantly, the noise is gone. I pulled the tube and ran the amp and blower and there is no noise. I can tap the tube slightly and it does in fact rattle a bit. Not anything broken but it does have a chime to the filament. The tube runs full power and tunes up great. Has anyone had this kind of thing happen? Is this a fault of the tube or maybe my filament supply? I have tried everything to silence the noise with no luck. Its a very high pitched rattle that really gets into your ear and annoys the hell out of me. Is this a magnetic problem? I do not thing it is just vibration.