The All American Five

[Nowhere-Man]

I got so used to parallel filament circuits that some random maths around a series heater chain seemed unusual. I wonder whether such a design would be legal today too. No transformer! Many only had single pole mains breaker switch. Chas Miller once stated he used to get irritated by the dire warnings over line chord droppers (disliked due to the heat). The so-called hot chassis American radios have a reputation as people got buzzed by cover fixing bolts or grub screws. Cosmetically though these radios were impressive and bakelite design with nice tuning dials. Apart from the dangers of high voltage they are great to restore as the circuit is very basic. Many had selenium rectifiers and half wave was typical. One gripe was they can get hot as the valves are crammed in a smaller confinement. This radio was built to be serviced and they can be restored easily - I would say the battery sets were trickier by comparison. I may have spotted one in a 1950's movie in black and white - not sure how many were exported.

[Hartley118]

I've long admired the All American Five as an example of US effective and economical design. Compared with British sets of a similar period, it's so much neater and lighter in weight. In fact When I used to travel to the US on business, I brought back several examples in my hand baggage. I fear though that today's airport security regime would throw a wobbly if I tried it now!

My examples carry evocative brand names like Westinghouse, RCA, Emerson, Zenith and even Hallicrafters. All have pretty similar circuits and work well on their intended 115V supply, so no line cord or dropper problems. Even the live chassis is less risky than on a 230V supply.

Interestingly, all work well on a few feet of wire as an aerial. I guess they were designed that way, much like a car radio. Sensible when compared with the common U.K. requirement of a 50-foot external wire. I get the impression too that the US sets typically incorporate a little beneficial positive feedback round the IF stage, whether intentional or accidental due to the compact layout. Either way, it helps both gain and selectivity.

They're nice examples of US post-war affluence, when a household there could afford several sets, whereas the British family made do with extension speakers.

Martin

[Nowhere-Man]

I agree they are a very clever design. I think old and simple engineering has a lot in its favour. What a good idea to simply drop voltage to supply heaters, lamp and then the main HT. They were reliable and practical. I imagine in those days the shops did routine repairs and valves were cheap to replace.
Today by chance someone gave me an old book on radio history with crystal sets as well. Lots of photos and even comic book advertisements. One advertisemment claimed a radio with loudspeaker output with no HT battery or valves. Just crystals.

[reset]

Yes In the 60's the shop I worked in did repair a lot of them. Cheap was relative the tubes were from 60 cents to a $1.10 each which sounds cheap but I was working for 70 cents an hour back then, but the repair bill was much less than a new radio. The local drug store had a tube tester just inside the door. A lot of people would test their tubes at the drug store before bringing the set to the shop. Quiet a few would tighten the loose screws too. Usually my repair included putting the tubes in the correct socket and an alignment!
I bought a new radio last week that suffered from the previous owner tightening the loose screws .

   

This one is made for airborne service and operates on 24 Volts DC. It is 4" X 4" X 6-5/8". The sales slip was attached to it. It was $12.95 new. Sadly I paid more than that in postage .

[Nowhere-Man]

I have an Ultra which is mid 1940's. It almost set on fire when I tested it but I killed the mains rapidly. After that I worked on it and cleaned it up as well. It then played OK and was one of my successes. Sadly a 1938 Halcyon I had worked on would not draw filament current and so I never applied HT. And I fear the Cossor valves would be costly. Thus my oldest set is 1940's and picks up stations very well. I don't know how many American Five sets are to be found in the UK but I always admired the design and the dials. Some are small enough to pass as transistorised.

[reset]

I have an Ultra which is mid 1940's. It almost set on fire when I tested it but I killed the mains rapidly. After that I worked on it and cleaned it up as well. It then played OK and was one of my successes. Sadly a 1938 Halcyon I had worked on would not draw filament current and so I never applied HT. And I fear the Cossor valves would be costly. Thus my oldest set is 1940's and picks up stations very well. I don't know how many American Five sets are to be found in the UK but I always admired the design and the dials. Some are small enough to pass as transistorised.

I searched for so data on the tubes in the set and found a replacement output tube listed for twice what I paid for the radio!?!
Fair Radio has added the set to their inventory and I can buy a new radio cheaper than the replacement tube? If it dies I guess I can by another and use it for spare parts.

[pwdrive]

https://fairradio.com/product/bc-1206/

Lawrence.

[Terry]

Would a live chassis radio be legal today? I don't see why not, provided it complied with BS415 (actually its modern BS EN 62368 equivalent).

I used to have a copy, many years ago, and it was a wondrous document, full of test fingers, test pins and even a test necklace for various tests to ensure that no live parts could accidentally be touched by the user.

It must be remembered that live chassis TVs existed well into the colour TV era. However, a continual move away from valves, not to mention the demand for SCART sockets, and the widespread introduction of switched mode PSUs brought about their demise in the 1980s. Radios, of course, had succumbed to total transistorisation and low voltage operation - even when mains driven - much earlier.

The introduction of safer components, such as potentiometers with nylon spindles, made the production of live chassis radios progressively more simple. So long as all exposed fixings, such as those holding the back cover in place, are isolated from mains contact and the ventilation slots do not allow accidental contact with live parts, I see no reason why someone could not release a live chassis radio on the market today - if they can find a source of suitable valves, of course!

The line cord was a necessary evil with imported sets of US origin (or originally designed for use in the US) because of the necessity of dropping the 120V excess in the UK mains voltage to the 117V required by the radio. There would have been no space available for a dropper inside the set and, even if there was, the sets weren't designed to accommodate the heat dissipated by such an item,  making a line cord the only way to go.

The problem was that customers would insist on hiding them under the carpet or, worse still from the point of view of the set itself, cutting the cord short!

I'm sure that some UK manufacturers used similar design practices but took advantage of the higher mains voltage to increase the HT. I say this because I recall, when I first started work, coming across some dusty line cords sold by Radiospares, as they were called in those days, which had taps built into the line cord so that there were two wires in and three out!

[ppppenguin]

There's plenty of live chassis kit around today. Think of central heating programmers, electric toothbrush chargers etc. All have passed safety tests. No reason why a radio or TV shouldn't have a live chassis and be safe. Except that in practice once you're beyond a certain level of complexity you've usually got interfaces that need to be safe so it's cheaper and easier to design in a SMPS with isolation or put the live bits in a wallwart.

[Murphyv310]

I could never really understand why imported sets didn't use a capacitor dropper. Suitable capacitors were available, pricey perhaps but the thought of a hot cable with children and it tucked under the carpet makes me shudder.