TV trade? That will cheer up Big Tony no end,
inshallah.

For myself I concur 100% with what you're saying. Remember
Meccano? That's where it all began for blokes of my era, I reckon. It certainly was in my own case.
Sadly, I have met too many techs who aspire to be biomeds (not all of them youngsters, either), who in my opinion (and, as you must know, I'm always happy to advise, good or bad) need, shall we say, to look elsewhere for their vocation! They simply lack the
enthusiasm for all things technical ... from anaesthetics to x-ray, and ASCII to Xenon (if you see what I'm saying).
Frankly, some folk see it (biomed, that is) as an "easy job in comfortable surroundings" ... and then spend most of the time whinging about pay grades, perks, and all that [censored]. In fact,
money seems to be their main motivator. Missing the point (and dare I say, the
joy) of the thing by a good Country Mile.

But was the diode polarised? In a way, yes ... why not? It sounds to me like the guy was well on the way to an understanding of what was going on!