Quote:
Originally Posted by G.Castle
I have one. (A local product i believe), they're not perhaps up to todays safety standards, but if run through a rcd protected supply and you use a one amp fuse in the plug/spur then they are no worse than any other vintage gear. I can't see how they could be a major fire risk. An insulation test may be an idea if you want to put your mind at rest.
It's in the Australian culture that consumer items should be powered from double wound transformers and have the crap earthed out of them, but then I don't know if they had a bigger prcentage of house fires caused by burning transformers than perhaps Europe or the USA?
I have three core mains flex on mine as it seemed the sensible thing to do.
Regards,
Greg
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Only radios, TVs and other such "Electronic" equipment used "double wound" transformers.
Other metal cased electrical equipment had Earth connections as standard, but used direct Mains connections.
If was not uncommon in Australia for houses to be supplied with 3 phases.
In the (maybe unlikely) event that two different phases were present in the same room feeding different GPOs, & devices operating from them had Active to case shorts, you would have full phase to phase voltage between them.
If the metal case is earthed, both devices will blow the fuses feeding them, & there will be no danger.
If, in the case of both GPOs being on the same phase & one has an earthed metal case & the other not, if the latter has an Active to case short, touching both simultaneously is dangerous.
As far as radios, in particular are concerned, at the end of WW2, Australia did not have the plethora of different power supply systems the UK & Europe had, so did not have the requirement for the radios to be usable on both AC & DC Mains.
We also didn't have 110v Mains, which in the USA made "series string" heaters a lot easier to implement than in 240v countries.
What we did have was valve manufacturers who had vastly ramped up their manufacturing capabilities of 6.3 volt valves during WW2, so instead of setting up new production lines for "series string heaters", it made solid economic sense to use power transformers & produce "ac only" radios for the mass market, with the few DC Mains areas, being regarded as "niche" markets, where special radios using imported "series string" valves could be used.
Interestingly, most such radios used "figure 8" cable, as with the Mains confined to the on/off switch & transformer primary, there was little danger of a Mains to chassis short.
Power transformer design was a mature technology, & fires caused by burnt out transformers were pretty much unheard of.
Transformers stink when they burn out, so in a domestic environment will soon be detected, whilst in commercial service, electronics with power transformers have run continuously for decades.
Yes, transformers did fail, but not catastrophically, & were just replaced & the equipment put back into service.