Quote:
Originally Posted by Electronic M
Here in the states it seems like polarized plugs on TVs became mandatory in the early 70's. Some brands (Sears) seemed to pick it up across their TV line much earlier, others started with hot chassis sets, and later did all sets.
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It's all about U/L approval and purchasing-inventory issues. Instead ordering two different types of A/C cords and interlock connectors, they just ordered one type. Also minimized installing the wrong cord on the various models.
On a side note: I always wondered why Motorola used some 3 volt tubes connected in series on some of their sets, even though the set used a power transformer and 5U4.
It stated in the Motorola Service News that the purpose was quantity buying, as they built as many or more series-string, transformerless sets, than the transformer models.