Sometime in the late 1970's Robin bought himself an upmarket cassette recorder. Heino remembers it as a SuperScope; I remember it as a SilverScope but I suspect Heino's correct; it was packaged in late 70's silverised plastic. You know the kind of thing, the slightest touch and the coating rubbed off and made the whole thing look tacky, which is probably why I'm remembering the word 'silver'.
The recorder came with a mini headphone jack but Robins headphones had the large style. They've been manufacturing adaptors for just such problems for at least 40 years that I know of but Robin decided he could do better than that; he was going to replace the headphone jack entirely.
So he cracked the case to check how much space was available. It would be a tight squeeze but it was doable with care and I'd guess it should have taken 15 minutes from go to whoa. Ever watched a hasty man make a chair out of packing crates using a blunt axe? I haven't either but that's exactly how I'd describe Robins approach.
Six or so hours later the recorder was half patched back together. The hole he'd enlarged was too large and the new jack wobbled about. Every so often one of the contacts would short against a pin on the PC board. One of the rubber belts had come off badly in an encounter with the soldering iron, which imparted an interesting stuttering effect to both recording and playback.
But he was proud of the result and, in the end, that's all that really matters, isn't it.