General > General Technical Chat

The "All American Five", & more dangers!!

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Mp3:
It's a tradeoff. You guys get to power a jackhammer off the outlet in your kitchen because of 220/240v, we get to be more careless with mains due to the lower voltage.

In regards to the earthing aspect.....
Japan does this as well and is actually worse because the earth in Japan is the screw on your outlet. Likewise, an American came up with the lightning rod method of grounding :D So does it come as much surprise that our design philosophy is to do as much work with as few parts as possible?

I mean, does it really matter on 100-120v mains? My whole life i've plugged things in either way around and they work. If the plug isn't polarized so it can only be put in one way. And even then, the majority of American households made before the later-mid 1900's out here have awful nightmarish electrical wiring.

Half the outlets in my apartment built in the late 1800s - ancient as far as USA buildings go - are wired backwards. The worst that happens is a spark when you plug something in. (I know, some of you in other countries probably can't fathom that, but it's one of the joys of low mains voltage)

Anyway, if you look at trends in American design philosophies, we have an affinity for having a minimal amount of components do a large amount of work. A lot of designs that came out of the USA that compete with European/Australian/Asian designed boards are way more overbuilt, way more simplistic, and expected to be treated MUCH worse IMO. (We are really rough with our belongings compared to other nations, I think)

vk6zgo:

--- Quote from: GlennSprigg on April 27, 2020, 01:16:40 pm ---(Please don't move this. It's mainly about 'general' topics).. :)
The "All American Five" refers to the mass produced valve radios, by very many manufacturers, from the 1930's. Apart from the standard 5 tubes & their functionality, their emphasis was on 'cheapness' of manufacture. There is/was NO power transformer, and relied on the American line voltage of 110/120-v to directly feed Plates (partly via resistors), and series connected tube 'heaters' of higher Filament Voltages etc., so that no mains transformer is/was needed.  OK, I get it, but half the time, one ended up with a 'Live' Chassis for the uninitiated!?  :P

So many times, I've seen ccts where a 'power' switch, if any, actually switches the Neutral!  The VAST majority of power plugs I've seen in America have only 2 pins, and no 'Earth' pin. Now I know that most 'modern' plugs/sockets there now are 'polarized' by way of a slightly wider pin, but still with no Earth??  I understand too that this is 'just' 110v, not 240v like in Australia, but I don't understand the attitude. I see numerous Youtube videos where people in the U.S. plug equipment into un-switched outlets on their bench. Ok, YOU might have wired it correctly.  :(

In Australia, we MUST have an Earth too, unless the device/machine is 'Double-Insulated', like a certain hair dryer etc. It just seems that America is more blase' about Neutrals & Earthing ?? (And yes, I understand about isolation transformers & isolated Variacs etc.)  :phew:

--- End quote ---

--- Quote from: GlennSprigg on April 27, 2020, 01:16:40 pm ---(Please don't move this. It's mainly about 'general' topics).. :)
The "All American Five" refers to the mass produced valve radios, by very many manufacturers, from the 1930's. Apart from the standard 5 tubes & their functionality, their emphasis was on 'cheapness' of manufacture. There is/was NO power transformer, and relied on the American line voltage of 110/120-v to directly feed Plates (partly via resistors), and series connected tube 'heaters' of higher Filament Voltages etc., so that no mains transformer is/was needed.  OK, I get it, but half the time, one ended up with a 'Live' Chassis for the uninitiated!?  :P

So many times, I've seen ccts where a 'power' switch, if any, actually switches the Neutral!  The VAST majority of power plugs I've seen in America have only 2 pins, and no 'Earth' pin. Now I know that most 'modern' plugs/sockets there now are 'polarized' by way of a slightly wider pin, but still with no Earth??  I understand too that this is 'just' 110v, not 240v like in Australia, but I don't understand the attitude. I see numerous Youtube videos where people in the U.S. plug equipment into un-switched outlets on their bench. Ok, YOU might have wired it correctly.  :(

In Australia, we MUST have an Earth too, unless the device/machine is 'Double-Insulated', like a certain hair dryer etc. It just seems that America is more blase' about Neutrals & Earthing ?? (And yes, I understand about isolation transformers & isolated Variacs etc.)  :phew:

--- End quote ---
The AA5s were more a thing of the 1940s on.
If you look at most published 1930s US radio designs, they used power transformers, with secondaries of from 285 to 385 volts "a side".

Factory made Radios were fairly expensive  back then, & a lot of circuits were designed for a fair bit of output power for use with the fairly inefficient "Electrodynamic".speakers in common use.

After WW2, the USA manufacturers wanted to produce cheap radios.

For some reason, power transformers were expensive, & "series string" tubes fairly inexpensive.
This, along with the fairly low (then) 110v Mains supply, lent itself  to the "AA5" design.
Other developments, like more efficient "Permag" speakers, & improvements in tube efficiency also contributed.

In Australia, the economics went another way:-
Tube factories had massively increased their production during the War, but virtually all the tubes they produced were in the heater voltage values  of 1.5v, 2.0v, 3.0v, 6.3v (the vast majority) & 12v.
There were also, in the early days, many hundreds of surplus tubes on the market, mostly 6.3 volt heater types

Higher voltage heaters suitable for "series strings" were not normally made, & usually had to come from the USA, the UK, or Europe.
The higher Mains voltage in Australia also made the case for transformerless designs much less compelling .
Transformers for domestic radios were neither excessively large or heavy, nor, in the Australian context, expensive.

The upshot was what became fairly standard in this country----- a 5 "valve" "mantel" radio  using a power transformer, a tube rectifier, a mixer, one stage of IF gain, then a detector/audio driver stage (a "double diode, hi mu triode") & an audio power tube(usually a beam tetrode of the 6V6/ 6AQ5/6M5 ilk.

There were a few "transfomerless" radios around----some custom made. for the few remaining DC Mains Supplies.
Of these, some were 110v DC, & the relatively simple "AA5"type circuit could be used.
Others were 240v DC, & the radios were messy things with series resistors, "barrettors", etc.

Transformerlesss designs were dubbed "death radios" & loathed by radio servicemen.

nfmax:
Transformerless TV sets - known and marketed as AC/DC designs - were very common in the UK. More valves makes series heater strings feasible with 240V mains. Surely the AC/DC TV set must have been a thing in Australia, of all places?  :)

vk6zgo:

--- Quote from: nfmax on April 30, 2020, 08:55:55 am ---Transformerless TV sets - known and marketed as AC/DC designs - were very common in the UK. More valves makes series heater strings feasible with 240V mains. Surely the AC/DC TV set must have been a thing in Australia, of all places?  :)

--- End quote ---

Nope!
When TV arrived in Oz, the valve type TVs followed the same pattern as the radios, using a transformer, with a 300-350v "a side" at 300mA secondary.
The early ones used things like 5V4s for the rectifier.
They soon moved to silicon diodes, for a while retaing the centre tapped HT winding, then later, 200-odd  volts non tapped windings with a voltage doubler.

By 1956/57, DC  Mains supplies were reasonably rare in Australia,  so the advantages of being compatible with AC & DC were not very compelling.

The only AC-DC TV I remember being sold here was an early Admiral "portable" .
It was hardly that, as it needed to be plugged into the Mains.
It didn't sell all that well, & was discontinued after a few years.

A lot of people worry about the weight of power transformers, but. you can hold a "mantel set" transformer in the palm of your hand, & carry it around,
Similarly, you can pick up & hold a BW TV power transformer in the same way although your  hand would get a bit tired after a while.

After having become used to carrying Australian BW TVs, I picked one up in England, expecting it to be lighter, but, too my surprise, it felt about the same.
I think much iof the weight of such a TV is the tube, chassis material, & the extra safety stuff which is not needed on the transformer equipped  version, leaving the relative weights pretty much the dame.

When colour TV came to our shores, we went straight to standard SMPS in the locally made TVs.
The imported (mainly Japanese) TVs did the same.
Both sides of thei Mains were isolated from the chassis, with the only connection to it being on the secondary of the high frequency transformer in the switchmode.

We never had the SMPS built around the Horizontal output circuit that was evidently common in UK & EU.
.







16bitanalogue:

--- Quote from: james_s on April 30, 2020, 04:41:44 am ---
<snip>

[Yes Nader's book did help kickstart some important changes, but calling the Corvair "unsafe at any speed" is pure hyperbole. Sensationalism to sell books.

--- End quote ---

I'll quickly summarize your position:

"It is owner's responsibility to understand our cheap, flawed, mass market design."

Be honest, did you even watch the video you posted?

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