Watts are supplied by the amp, not the speaker. As long as your replacement speaker has a equal or higher wattage rating than the original equipment, you're good to go.

You're good to go. There's isolation from the amp via the power transformer. So long as there's nothing going on in the amp, there's nothing coming out of the power cord. Play on!

the focus knob on binoculars is basically a nut that drives a screw, which adjusts the distance between the objective and the eyepiece. If the knob turns, and the eyepiece does not move, there's a mechanical defect.

two issues: 1. battery voltage is greater than solar voltage. Current flow is from highest potential to lowest Solar has reverse flow (diode) protection. Ergo, no battery charging going on. Also, blown fuses in current meter (multimeter) mean no circuit, also no current flow. Cheers KC8KK