looking at the picture and considering the amount of crud on the outside of the blower, I'd suspect that the blower internals might be just as cruddy if not worse causing an imbalance of the internal fan/squirrel cage and causing vibration.
There was a ton of hardened dust in the blower wheel. I’d already cleaned it out with compressed air and a toothbrush, the wheel is clear and the motor lubed up, before I ever powered it up. This picture was what it looked like before, it was handy to show the coil, but isn’t what it looks like now...
A previous owner had replaced the stock umbilical cable with a large C-J connector, including the 3kV B+, which in stock form was on a Miilen connector. I’ve put a plate over the hole with an SHC connector, a Powercon ac inlet, and a third connector to my home brew power supply to activate the relay that powers it up. I also replaced the rca input with a BNC, and the beatup SO 239 output with an N connector. The metering resistors were mostly replaced as well. The whole thing was in much worse shape than I thought, I paid too much, but, as the say, in for a penny, in for a pound, so it’s now just about ready for rf.
But back to the noise:
The level of vibration is higher that it should be but it isn’t imbalance from dirt, it’s more like 60Hz hum. The motor runs hotter than I’d expect, too. Do these blowers have a capacitor in them?
Ed