Common items you passed up that turned rare when you wanted them

A few very early UK TVs had mains transformers, and even produced the EHT (about 7kV) from that. That supply could source considerable current and was lethal. A few later TVs had mains tranformers, but were often live-chassis too. The mains tranformer might be for the heaters only, or might be an autotransformer, or something like that. Be careful if working on one of these. Most B&W TVs had series string heaters (the P-series 300mA valves). There were oddities with some 100mA nand 200mA strings in them them, but you're not likely to find one of those. The HT (B+) line came from half-wave rectifying the mains, either using a valve (U291, PY32, PY82, etc), or a contact-cooled selenium rectifier, or a silicon diode depending on the age of the set. The EHT came from the flyback transformer, of course. Most colour TVs had a mains transoformer, if only for the CRT heater. But again you might find a series string of heaters (possibly fed from a tap on the transformer), and the HT line would come directly from the mains. Of course modern TVs have an SMPSU and an isolated chassis, if only to simplify the circuitry for the SCART connector (this has composite video I/O, RGB in, audio I/O on it, isolating all those signals would be a lot more work than an isolated SMPSU). In UK sets, the horizontal output valve (line output valve, something like a 30P4, PL36, PL81, PL504 depending on the age of the set) and the booster diode (damper to you, soemthing like a U191 or PY800) were in the normal series string. -tony