Having replaced the power switch on my workshop vacuum it appears that there are other problems too. When run in “normal” mode it seems fine (other than the volume, which I’ll come to in a moment), but if I plug my chop saw into the power outlet and have it switched so the vacuum runs at the same time as the saw, the motor starts “pulsing”. I’m guessing there’s either some odd feedback thing going on with the power or there’s another fault somewhere else in the electronics. I’ll try on another piece of equipment tomorrow.
Had it appeared to work properly then I’d have thought about dealing with the noise issue, which I think is likely to be down to worn out bearings in the motor. I can’t seen the point in putting in the time and effort to deal with that if I can’t really use it the way I’d like however.