Are you postulating a 'vanishingly improbable' combination of faults, or what? If the primary problem were the exploding of C1, then no 'fuses' (whether real fuses, destructing resistors or necked tracks) would operate until after the damage had been done. On the other hand, if the primary problem causing R1 to destruct were something other than the explosion of C1, then, as I said, it would surely be incredibly improbable that C1 would simultaneously explode, wouldn't it?
If, over the years and decades, I had not 'destructively examined' many things which were probably perfectly functional (in order to hopefully rectify a 'lack of understanding'), I would undoubtedly have far less knowledge than I now do!
Indeed. I would actually think 'next-to-impossible'.
Maybe, but the aluminium foil itself would probably go a long way to representing such a 'fuse'.
... which, in turn, is obviously a consequence of consumers desire/demand for the lowest possible retail cost. Many of the manufacturers probably do give consideration to the common failure modes (hence that 'necked' PCB track), but to cater for all conceivable modes of failure would undoubtedly result in unrealistically high costs/prices. As for 'commoness', I imagine that explosion of the capacitor is, in itself, very rare, and that in probably "99%" (certainly a very high proportion) of the few cases in which it does happen, there would be no significant 'secondary consequences' (due to 'flying foil' etc.).
The big problem as time went on was that we ended up with multiple such units connected together - TV, VCR, satellite receiver, Freeview receiver, DVD player etc. - and the combined leakage currents are not inconsiderable.
Zener diodes in those locations make sense to provide the necessary reference voltages for the regulating action of the supply.
Even though a 500V DC test may have revealed no sign of impending breakdown, it still looks like a very cheaply made transformer if that blue tape was the only thing separating the primary and secondary windings. But that's exactly what all this stuff is - Cheaply made, both in price and quality.
Even expensive transformers often only have the windings separated by mylar tape.
You can bet it's better quality and more care taken with construction than with that in the transformer in some $6 USB charger though.
Of course. Those who want to pay for a more expensive product bearing reputable branding are free so to do, and will usually (but not always) get a product which, at least in some senses, is 'better'. However, there seems to be a large market for "as cheap as possible" products and those who make that choice will 'get what they pay for'.
Which might be death of themselves or a loved one.
That's often a major part of the problem. The branded product from a reputable manufacturer will undoubtedly be 'better', but not "14 times better". If these manufacturers were less greedy in terms of profit margins, the incentive to buy "cheap (and possibly dangerous) tat" would undoubtedly decrease appreciably. Just like you, I would probably pay £10 (or maybe even £15-£20) rather than £5, but not £70.
