MC your a party pooper! :-) Take the fun out of a fart. LOL
I’ve fixed a lot of hums, that’s for sure. But I don’t run 10 different kinds of Tonearms either. I’m a SME guy from way back. I ran a lot of Grados too, they were known to make noise. I fixed them all unless there was a cart winding failure. When I would inspect 90% of the time it was a very tiny frayed tube wire or a single stray just close enough to cause problems but almost impossible to see.
A sniffer will find it, if you screw up any ways.. I’ll find the schemo on how to build one.. They work great.. Can work for a noisy tubes too. What about that? Just need to be able to check your work..