So this is probably more of a general question, but the fault itself lies in a 24 I recently found at a thrift shop.
I knew it was too good to be true - excellent condition, brush bar spun fast, relatively clean. So anyway, I turn it on and it actually hurts my ears. I then had to plug my ears with paper after I took the HEPA filter out. There are visible sparks but they appear to be the normal sparks which lie between the brushes and the armature. I'm assuming this means the motor is not long for the world, but I am hoping for a second opinion.