You can literally short the input to the amp and be fine. In fact, cheap cables do this all the time. There would have to be a major issue with the amps isolation between the preamp and power amp to have an issue. This is possible, but a rusty pickup is not really the issue. You're simply ill-informed. It happens to the best of us.
Have you ever studied Samuel Goldwasser's PhotoFacts?
I have. I've actually studied it so many times that I know the typical failure mode of electronic components in almost any situation.
Amplifiers are powered by transistors (or tubes back in the day, not much difference). When they happen to be stressed to the point of failure, they practically always fail as a short circuit.
Short circuits aren't fun, that's why they invented the Variac to properly test suspicious devices.
Edit: I hate to repeat myself, but would you plug in a rusted toaster? Do you not value your life, or would you rather test the components and clean things up first?
Nobody asked you what you could build from fresh scratch, I'm asking you what you'd do with electronics that have 15+ years of salt water vapor damage...?
Yes, I have experience with old electronics as well, and guitars, repair work, the whole lot. And I have an bs in EE.
But none of that matters because what is really happening here is that you are wrong, and instead of learning and moving on with a better understanding, you are tripling down and pulling the wool over your own eyes.
And you and all of your friends are dismissing safety. Fuck all that, I respect safety and always have. You've got mains going into the amp, the cable going into the guitar, and metal wires on the fingers. Oh, don't forget about the metal whammy bar...
Although the risk of electrocution is minimal, it still exists. My folks had a rule to not fuck around with sketchy equipment. What the fuck is your deal with cleaning and maintaining a goddamn guitar?
Lol. Nobody is saying to not maintain a guitar, wtf. What a wild stretch. You must be defensive.
They are just saying that you are wrong that a rusty/shorted pickup is some serious safety risk. Because it is not, and you are acting self-righteous, ill-informed, and paranoid.
Yeah, and the guitar only has 5 of 6 strings, and some nitwit asked how it sounds...
Get real, lemme ask you how a 6 cylinder engine would sound with a dead cylinder. Lemme ask you how a motorcycle would drive with a broken spoke or two...
Nothing that relies on timing is gonna sound right without proper maintenance. I mean goddamn, at least WD-40 the existing strings and tune them first, how TF anyone gonna judge the sound of a corroded guitar without a basic checkup and cleanup?
No, I did not forget my point. I'm referring back to the start of my points, which all basically add up to inspect, clean, and repair the thing before hooking it up to any device connected to mains electricity.