so ... after a couple of years, with the help from this forum (especially @jayeff @pe1rfe - thank you!), ChatGPT, [link|https://www.udemy.com/course/crash-course-electronics-and-pcb-design/|Crash Course Electronics and PCB Design|new_window=true] a local reair cafe (https://cambridgecarbonfootprint.org/repair-cafes/) I have finally managed to fix my Killburn!
In my case, the fuse was blowing due to two fried diodes in the bridge - they had very low resistance in either direction, while the other two were ~400Ohm in one direction, and very high in the opposite. I ordered replacement S2M and a kind sole at the local reair cafe swapped them in 10 min or so. The speaker is working again! Exiting but long journey - still, was very satisfying (much more so compared to buying a new one) !
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