The All American Five

[Nowhere-Man]

Remember we are discussing transformerless sets, plus hot chassis on some designs. Even in the 1930's isolation via transformer was a domestic consideration. It's a fair point American voltage was 115 so although people got shocks I doubt anyone got electrocuted. Still these sets have had their critics due to this direct supply of voltage. Certain makes even in America had a nasty reputation. I recall one guy was carrying his radio, touched a bolt and received a decent buzz. As to capacitor droppers they only tried that first in the 1970's on TV sets so in the 50's it was a bit early I suppose. I seem to recall you can but 250 - 120 converters in Maplins so then an AA5 could be used. I wonder how common they are here?

[Nowhere-Man]

The term used was "widowmakers" for some of the more basic models.
"After public outcry and several sensational press accounts[citation needed] of the problem, the hazard was eliminated from later sets by the use of an internal ground bus connected to the chassis by an isolation
networkThe metal chassis securing screws were often accessible from the outside of the Bakelite or wood case, and there were many examples of owners receiving a shock by making contact with these screws while handling a set."

[ppppenguin]

The whole business of live chassis sets was driven by low cost and, to a lesser extent, by reducing size. A mains transformer was an expensive and large component. In the earlier days, much less int he 1950s, there was also DC mains in many areas. So live chassis sets became common on both sides of the Atlantic. The valve makers made valves suitable for series chain operation, something that was easier for 115V mains than 240V. Again no set designer really wanted a big, hot dropper resistor and in the 1950s a dropper capacitor would have been large and expensive. For HT, life was easier here, as rectified 115V was a rather low voltage unless you were using valves designed for battery sets.

As Trevor has said, line cord was a horrible but cheap way to drop the voltage. Complete with asbestos to add to the hazards.

In some countries, such as Australia, live chassis was rare. Was it illegal there? In the UK at least it was absolutely standard in TVs for several decades. A TV would need a big mains transformer and the magentic field could affect the picture. The Thorn 2000 I'm working on is a rare exception. It has a hefty mains transformer carefully designed to have low external magnetic field. Heavy and expensive but the only viable way in 1967 for a solid state colour set.

Safety regulations tend to play "catch up" rather than being ahead of new products. And manufacturers will always be tempted to do the bare minimum to comply. Even as late as the 1960s "Which" magazine was reporting TVs that barely met the accessibility requirements for live chassis operation. Now of course we have widespread infringement of the CE marking rules. Notably on phone chargers.

Plus ça change, plus c'est la même chose

PS: I thought the term"widow makers" was used of early TVs with mains derived EHT. Truly lethal to service techs.

[Murphyv310]

And don't forget microwave ovens, the voltages and current available is as lethal as any mains derived EHT set.

[Synchrodyne]

In some countries, such as Australia, live chassis was rare. Was it illegal there? In the UK at least it was absolutely standard in TVs for several decades. A TV would need a big mains transformer and the magentic field could affect the picture. The Thorn 2000 I'm working on is a rare exception. It has a hefty mains transformer carefully designed to have low external magnetic field. Heavy and expensive but the only viable way in 1967 for a solid state colour set.

The same was true of New Zealand.  Radio and TV receivers for the most part had double-wound power transformers.  I am not sure if the live chassis approach was actually illegal.  But I did hear once or twice that some of the electricity supply authorities prohibited or at least strongly discouraged such equipment because it put DC on the power supply system.  But for whatever reasons, the Australian and New Zealand setmakers chose the “high road” where power supplies were concerned.

That power transformers might be deleterious to TV receiver performance was I think one of those potential but not actual problems that the UK setmakers (or their supporters) made more of than was warranted in an effort to justify their use of corner-cutting implied by live-chassis power supply arrangements.  NZ TV receivers seems to work just fine despite their inclusion of power transformers.  And this applied to derivatives of European models, such as the Philips K9, whose original versions lacked this feature.

Also, as far as I know some of the UK setmakers offered industrial receiver/monitor versions of their domestic models that did include double-wound power transformers, and presumably these were to some extent sold into markets where picture quality was more critically analysed than in most of the domestic market.  So, there were obviously no insurmountable difficulties.  Occasionally that good practice spilled back over into the domestic market, as with the Decca Professional 23.  (Which also had line-gated AGC on both systems, something that some of the lazier setmakers would have argued was too complex/too difficult for the domestic market.)

From there it is not a major leap to suggest that in perpetuating the live chassis technique for receivers that were only for operation on AC power supplies, the setmakers were to some extent treating their customers with contempt in respect of safety.  One may of course invoke caveat emptor, but then the typical customer for a domestic TV receiver would not have known enough to ask about power supply safety.  Perhaps had one or two setmakers used isolated power supplies and extolled their virtues, things would have been different.  And were the “consumer” groups mute on the topic?  For example, a good write-up in “Which” that in conclusion came out against live-chassis receivers might have stirred things up a bit!

Some of the UK setmakers offered both AC-only (with isolated power suppliers) and AC-DC (live chassis) versions of their domestic radio receivers, rather than issuing the latter type for all situations.  That implies that the AC-only type was thought to be a better choice where it could be used - which must have been the majority situation by the later 1950s.  If not, why do it?
        

Cheers,

Steve

[Terry]

From there it is not a major leap to suggest that in perpetuating the live chassis technique for receivers that were only for operation on AC power supplies, the setmakers were to some extent treating their customers with contempt in respect of safety. ...  For example, a good write-up in “Which” that in conclusion came out against live-chassis receivers might have stirred things up a bit!

Treating their customers with contempt in respect of safety???

Provided the sets complied with safety standards such as BS415, how could the customers' safety be compromised? The customer wasn't supposed to remove the back and there would be no reason for Which? to investigate or comment on the internal design - they were purely concerned with performance and even refused to take cost into account. Thus they would rubbish a perfectly good product (of any type) because it didn't perform quite as well as one costing twice as much!

One case in point was the Bush TV123 which was an economy version of the TV125 in a plastic cabinet with a rotary UHF tuner rather than push button (but otherwise identical internally) which was rubbished on the basis that the sound quality wasn't as good (because of the plastic cabinet!) than its more expensive brother with the wooden cabinet!

Similarly, although much later,  a (very) cheap electric kettle we bought several years ago - and still going strong - was rubbished by Which? because their sample didn't switch off until seven seconds after the water boiled! I've just done a quick calculation and, assuming we use it twice a day, it has consumed extra power totalling a fraction under 1 unit a year, every year. However, by the time we bought that kettle, Which? had got so ridiculous that we cancelled our subscription - so you could say that Which? has actually saved us a small fortune over the years!

Of course it was the service personnel who had to take care when working on those AC/DC sets which reminds me of when our shop was extended and a new workshop guilt shortly after I started work. Everything was virtually complete and waiting for the Electricity Board to turn up and connect the feed to the new consumer unit into the supply. The feed ran behind the original building line to feed us and the adjacent properties and now ran though a hole which had been left in the new concrete floor at the back of the shop.

So this chap turned up and spread out a rubber mat on the edge of the hole and merrily spliced the two cables together while we all looked on with admiration thinking 'blow that for a game of soldiers' or similar! When he'd gone, of course, we went back to the workshop and continued to manhandle large chunks of metal connected directly to the mains without a care in the world and not a rubber mat in sight!

[Murphyv310]

Which magazine was at one time the most biased publication on sale. I refused to have anything to do with it after some of articles were completely and utterly inaccurate.

[reset]

Some of the UK setmakers offered both AC-only (with isolated power suppliers) and AC-DC (live chassis) versions of their domestic radio receivers, rather than issuing the latter type for all situations.  That implies that the AC-only type was thought to be a better choice where it could be used - which must have been the majority situation by the later 1950s.  If not, why do it?
        

Cheers,

Steve

Steve,
Here at my house no power was available until the local power co-operative started supplying the area in the mid to late 40's. Even today developers have to pay to have lines ran from the main lines to new developments. Big city folks and youngsters who grew up with it don't realize just how new it is. Lines were ran to my house around 1948. The big city 40 miles away had a TV station about 1950. We had batteries before that.
Cheers
Greg

[Pat Pending]

In most rural areas of the UK the situation was the same, in fact the mass electrification was responsible for the drive to produce cheap(er) radio sets to sell to this newly powered demographic.

In the years that live chassis sets were in production there seemed to be a more common sense approach to safety, the sets normally had the warning printed on the back cover, and anyone who was electrocuted was deemed to have been to blame for their demise.

There were some real "shocking" designs, (pun intended), like the hallicrafters S-38, live chassis insulated from the metal cabinet with only a few small rubber grommets that soon perished, a non polarised mains plug and it's radio death roulette. The only saving grace in their homeland was the 117V supply. It was these sets in particular that were designated "the widow maker" in the US.

In those days the UK industry was also pretty bad, but with the added spice of the nominal 240V supply.
Even more insentive to keep the back on, and not pull off the knobs!

Having said that when these sets pass through our hands we do have a responsibility to make them as safe as possible and hang originality, even if they are only for our own use.

Andy.

[Murphyv310]

In reality there were allegedly very few deaths caused by live chassis radios and TV'S. People back then seemed to be more aware of the risks.
It would be interesting to see if this would be different now if there was a resurgence of live chassis equipment.