Talk:AC/DC receiver design

Regional variations

The difference between 120 V and 240 V AC mains is not particularly relevant to this article. I'm reasonably sure that at least as many people have been killed by accidental contact with 120 V as with 240 V, so a safety difference is non-existent and irrelevant anyway. There seems to have been no shortage of transformerless tube equipment of various power levels in North America. From wrecking old mono tube TV sets I found they all had power transformers for the B+ even if the heaters were series string - could we find a reference that says European TV sets didn't ever use one? It must have been cheaper to put in a power transformer than a voltage doubler - or perhaps there were other reasons. And it's still irrelevant unless such sets were intended to be run from DC mains, which I doubt. Anything with a phonograph in it would have been built for AC only for the motor, so the power argument falls out.

The article neglects AC/DC power tools; anything using a universal motor would happily run on DC, but I don't know if such tools were promoted for DC areas. (I have seen an old electric power drill nameplated to run on 25 to 60 cycles). I wonder if Google's old copies of "Popular Science" has ads for DC power tools? --Wtshymanski (talk) 15:31, 4 February 2010 (UTC)

"It must have been cheaper to put in a power transformer than a voltage doubler". Why so? A couple of diodes (vacuum, selenium, or solid-state), a couple of capacitors... The 8-valve dual-voltage radio I referenced uses 2 diodes and five 25 microfarad electrolytics. A non-doubling supply requires 1 diode, though I haven't bothered to work out how many extra capacitors the doubling feature requires (you'd use at least 2 without doubling).

"I'm reasonably sure that at least as many people have been killed by accidental contact with 120 V as with 240 V" I'm virtually certain that that's not so. Unfortunately I haven't been able to find any old statistics in the time available; in recent times everything is double-insulated and earthed to such an extent that electricity is pretty safe. Just as a rough idea the energy that will be dumped in a resistance is proportional to the square of the voltage, so 4 times more energy from a low-impedance power source, maybe more (or less) if the shock causes resistivity to drop (or increase).

Regulations in some 230V places require power tools used professionally to be rated at 110V and used of 230V through isolating (not auto!) 110V transformers.

I didn't say European TV sets didn't EVER use a power transformer. There were definitely TV sets without power transformers - they ran off DC. The HT off the mains wasn't enough, so it was boosted with energy recovered from the scan coils during flyback, but I doubt you could do this off 110VDC - see my comment in the article about the lower voltage available off 110V. If you want a reference see the Pye B18T. BTW, earlier AC-only sets used a mains transformer to generate the EHT, and produced enough power to electrocute an army. DC mains supplies were still quite common in 1948. I think this establishes beyond peradventure that 220V AC/DC was used for TV; and it's pretty obvious that 110V DC was not enough to generate the HT.

I know nothing whatever about AC/DC power tools or practical motor use.

I think what I write and reference here is enough to establish the validity and relevance of what I wrote in the article. I'm running out of time, so will simply reinstate what I wrote, and will add the AC/DC reference and tidy up later. Pol098 (talk) 16:50, 4 February 2010 (UTC)

A reference on AC/DC TV PSUs into the colour and semiconductor era: [1] Pol098 (talk) 18:14, 4 February 2010 (UTC)

Must have been cheaper, because that's how they were built. I suspect a voltage doubler might have required rather large capacitors and it would have been an interesting trade-off between costs of the two approaches; I suspect that another consideration was obtaining a filament supply for the picture tube, which was apparently not convenient to put into the series string with all the other tube filaments.

Blows my mind that there appears to have been 240 V DC powered TV sets! I've got to check out these links. (I once had to run a color TV off 240 V DC but that's another story involving a VFAC drive and learning all about inrush current).

I once looked at accident statistics for household electrocutions comparing Ontario and the UK. I don't have the links handy here and I can't recall exactly what my observations were; I think it worked out that electrocutions were a little higher per capita in Ontario, but higher per GWHr in the UK. Either 120 or 240 V is quite sufficient to kill a human, so the safety argument is a wash.

And we don't know that areas that now have 240 V AC once also had 240 V DC distribution - utilities could easily have changed voltages when they changed to AC. Early carbon-filament bulbs worked better at 110 than at 220.

Some tubes ran at 32 V on the plates...quietly, though. See All American Five and its talk page. --Wtshymanski (talk) 19:15, 4 February 2010 (UTC)

"Blows my mind that there appears to have been 240 V DC powered TV sets!" They were absolutely standard for many years, not the least bit unusual, though strict DC operation was becoming an irrelevance and I don't know if later ones were 100% DC-compatible (this is lack of knowledge, not specific doubt, who cared?), but certainly DC-boost circuits were common instead of a transformer. The most complicated TVs ever were probably from the late AC/DC era: in the UK the standard was changing from 405 to 625 lines over a few years so for quite a while there were "dual-standard" sets capable of handling both. + colour coming in. + AC/DC... While the 1946 one I mentioned was 240V only, there were probably 220-240V ones later. I think I've chucked out the book I had on repairing TVs, which would certainly have gone into detail on the subject.

I still think that 220+ VAC is a lot more dangerous than 110V, but you think it's not, and in the absence of mortality figures for the 1950s there's not much to say. Certainly there'll have been a lot more non-accidental electrocutions in the USA; I don't know if they're lumped in with accidental in the stats. (Later) I think any casual research into deaths by electrocution is hopeless; you need deaths specifically from 110 or 220V, there are so many other voltages used in industry, rail, etc.; and from about the 1950s when they were less safety-conscious. Pol098 (talk) 19:36, 4 February 2010 (UTC)

I've reinstated the statement that 220+V is more dangerous than 110+, with documentation. Pol098 (talk) 15:27, 5 February 2010 (UTC)

I see it's been reverted again with summary "long essay on electrocution hazard better suited to another article; still not proven that 240 actually killed more than 120, and beside the point for this article anyway. How about power tools? (Wtshymanski)"

As AC/DC is of historical interest only it's not an important practical point; but the whole article is mainly historical so it's as relevant as the rest. I've "always known" as a matter of practical necessity that 220-240V is more hazardous than 110-120, but am having difficulty documenting it, I think largely because electricity nowadays is pretty safe except for work where tools may cut cables. I've certainly always been a good deal more cautious around 240 than 120V. I strongly get the impression that the objection to this point is simply disbelief that 240V is more dangerous than 120V, rather than any issue of relevance; I note that the difference between AC/DC practice between 120V and 240V (voltage doublers and the like), which is highly relevant, was reverted due to disbelief before I documented it. There have been millions of 240V AC/DC TV receivers (and probably hundreds of models).

It certainly is justifiable by simple logic: it's well documented that the danger from electricity is due to current (it's volts that jolts, but mils that kills); studies of the danger document currents. Clearly 240V will pass about twice the current as 120V (I think that the body's resistance decreases as an effect of shock, so the current may be a bit more than double, but this is probably not significant). A 240V shock is certainly not necessarily fatal - I've had enough - so the argument that both 120V or 240V will kill so the difference is irrelevant won't wash. It's elementary formal logic:
(Premise 1) If the voltage doubles, the current doubles (known physics)
(Premise 2) If the current doubles the damage, and risk of death, increases significantly (known biology)
(Conclusion) If the voltage doubles the damage, and risk of death, increases significantly

To support this I provided references that safety regulations mandate the use of 110V (via an expensive transformer) where there is electrical hazard in a country where 230V is the norm; and quoted "it has been estimated that if this recommendation for reduced voltage for portable apparatus was universally adopted throughout the UK", though I haven't found the direct source for the estimate. Summarising, (a) it is plainly in accord with simple physics and biology that doubling the voltage increases risk of electrocution; (b) although I've not found a reference that says so explicitly (but none that denies it either), I have found regulations which mandate 110 rather than 230V where there is electrical hazard for safety, and an estimate that use of lower voltage would halve deaths; (c) the issue of the danger due to higher voltage is relevant to the article.

I have simply reinstated my last edit to restore many other changes to the wording of other points I've made, but am amenable to removing the point about the hazards of high voltage pending resolution following discussion.

Power tools: I have nothing to say, having no knowledge. Pol098 (talk) 18:55, 5 February 2010 (UTC)

Got it! Tables of the duration of touch exposure to voltage for 50% chance of ventricular fibrillation . For example (all tables show similar results) table 4, soil resistivity 10 ohm.m, 0.25 seconds at 222V, 0.40" @ 122V. Pretty conclusive; this allows the fairly long text I wrote to be dropped. You can touch 120V for nearly twice the time as 240V for similar risk. This is consistent with my argument from physics, biology, and logic above: assuming damage to be due to energy of shock, twice the voltage ==> twice the current ==> about half the time to dump the same amount of energy. Not exactly half, and it varies with various parameters, but the picture is consistent. I'll modify the article later to incorporate this. Pol098 (talk) 19:31, 5 February 2010 (UTC)

Too long,didn't read. Original research. Substation grounding design is not relevant to hair dryers falling in the tub, no matter how many anesthetized pigs are sent to hog heaven in lab trials. What are the actual statistics? The difference in risk of electrocution between 120 V AC and 240 V AC is of no practical significance and is quite irrelevant to the topic of this article. --Wtshymanski (talk) 20:03, 5 February 2010 (UTC)

Not a great article

This is not a great article at all. I don't see much substance and it's not even entertaining to read. I think it needs some work. I list a few things I noticed.

1. "The operation of the power supply is further described in another article".

This sentence is inappropriate. I would eliminate it from the paragraph.

2. "This type of equipment continued to be produced long after AC became the universal standard due to its cost advantage over AC-only".

Should it be "over DC-only" instead?

3. The "Modern equipment" section does not state what type of modern equipment is considerated, except of a reference to cars.

4. "modern equipment is often powered from low-voltage DC, typically a 12V battery in a motor vehicle"

This does not sound like a great sentence.

ICE77 (talk) 06:14, 5 February 2012 (UTC)

Switch-mode AC/DC supplies

I have run across instruments with midget switch-mode power supplies that are rated for both AC input and DC - I don't know what the general term is for these (universal power supplies?) but they tend to be in things like digital panel meters which sometimes get used in switchboards with DC control power. --Wtshymanski (talk) 19:45, 31 July 2012 (UTC)

Any switch mode supply that has a rectifier as the input stage will run from a DC supply (unless it has a switch). They may not be rated that way (as DC mains are rare (if they exist at all), but they will work. They often require a DC voltage that is higher than the specified AC voltage (typically 30-40% higher) to operate properly. 86.150.65.44 (talk) 18:00, 1 August 2012 (UTC)

Yes. But switch mode supplies that have a voltage doubler stage at the input will not work on DC. --Wtshymanski (talk) 20:23, 1 August 2012 (UTC)

True. But no claim was made otherwise. A rectifier and voltage doubler are not the same thing (though they are related). 86.150.65.44 (talk) 11:30, 4 August 2012 (UTC)

Diffence between AC and DC

There has been some edit warring on the method of pesentation of the differences between AC and DC. Three editors feel that it is best presented as a bulleted list as it makes the comparison easier for the lay reader. One editor only (Wtshymanski - who else?) has decided that it should be in prose. His prose version makes it more difficult to extract and compare the essential points. He has quoted the manual of style which favours prose but with this statement, "Do not use lists if a passage is read easily as plain paragraphs." The concensus here is that the information is much harder to read in prose form so that this not relevant. 86.150.65.44 (talk) 11:46, 4 August 2012 (UTC)

This article is about AC/DC equipment containing tubes from a past electronics era. The lede explains this and I quote:

The description AC/DC refers to electrical equipment designed to operate on either alternating current (AC) or direct current (DC). This term typically describes certain types of vacuum tube radio or television receivers. AC/DC equipment was necessary because in the early days of vacuum tubes, some regions were supplied with AC power, others with DC. Equipment which by its nature can use either AC or DC, such as heating devices and incandescent light bulbs, is not usually described as “AC/DC”.

This section regarding AC and DC theory is not related to the the article's topic whatsoever and should not be included here. The inclusion of this "training wheel" information distracts from the main topic badly and fattens the article unnecessarily. Should we be adding a section on Ohm's law or electron theory next? Perhaps some do not understand what the lede refers to and should not opine? Perhaps the lede needs to be changed to accomodate miscellaneous electronic theories as suggested? I feel the article needs to adhere to it's title and lede description. Base theories and teachings do not belong in this article despite how hard anybody has worked on these topic distractions.

Point form is fine with me and makes easy reading if kept short but is not the issue I am raising. Your ad hominem reference/attack is not wanted on WP and needs to be removed. Please discuss material and not people. 174.118.142.187 (talk) 23:02, 29 October 2012 (UTC)

Unrelated, off-topic sections make this article look amateurish!.

This article is about AC/DC equipment containing tubes from a past electronics era. The lede explains this and I quote: (for Pete sake read it!)

The description AC/DC refers to electrical equipment designed to operate on either alternating current (AC) or direct current (DC). This term typically describes certain types of vacuum tube radio or television receivers. AC/DC equipment was necessary because in the early days of vacuum tubes, some regions were supplied with AC power, others with DC. Equipment which by its nature can use either AC or DC, such as heating devices and incandescent light bulbs, is not usually described as “AC/DC”.

These bottom sections "Motorized tools and appliances" and "Switched-mode power supplies" are clearly not related to the article's topic whatsoever and should not be included in this article. I feel the article needs to adhere to it's title and lede description. Switching power supplies were not even heard of in the era of the AC/DC electrical equipment that the title portrays and the lede describes. Perhaps these sections are hangovers from another merged article and lost their homes? Take them out. 174.118.142.187 (talk) 23:42, 29 October 2012 (UTC)

I agree. But the lede isn't even correct. It states, AC/DC equipment was necessary because in the early days of vacuum tubes, some regions were supplied with AC power, others with DC.". This is not the reason AC/DC equipment came into being. AC/DC equipment first saw the light of day with the development of the All American Five design of radio receiver. The design objective was not to design a radio that would run of DC as well as AC, but simply to eliminate every possible component that it was possible to eliminate, in particular the relatively expensive mains transformer. The fact that the radio would also run from a DC supply was nothing more than a convenient side effect (at least to those few users who still had a DC mains supply). DieSwartzPunkt (talk) 15:08, 10 November 2012 (UTC)

Correct in every particular. What I find interesting is the claim that Murphy made an AC only radio that was 5 shillings (£0.25) cheaper than the AC/DC model. I cannot imagine what Murphy removed from the AC/DC design to arrive at an AC only design that would have saved 5 shillings. Does anyone have any idea? The only thing that I know of that can turn an AC/DC design into an AC only design is the inclusion of a voltage doubler input circuit to give a higher voltage HT rail but that would have added at least one rectifier and one capacitor to the cost (and certainly more than 5 shillings). 86.159.159.194 (talk) 18:09, 13 November 2012 (UTC)

Pol098 claims in the article that the complication was the inclusion of an autotransformer to boost voltages lower than 240 volts to the required 240 volts. But the idea that they could add a transformer and reduce the price by 25 pence is obviously just plain bonkers. However, this may just be a feature of a specific model and not necessarily related to the model where the price did come down.

the other thing that Pol098 cannot seem to come to terms with is that the AC/DC design was produced with the sole intention of eliminating the transformer (and THREE different editors here have said so). All the All American Five (the first ever such design) literature confirms this. That it worked off DC as well as AC was nothing more than a convenient side effect (though it did not work quite as well). A handful of DC mains only radio designs did exist prior to the AC/DC design, but they did not operate from AC. In any case, during the era when many households might have had DC mains, most radios were still powered from batteries.  :::I can even recall my grandfather having to walk the three miles into town and back every week to swap over the LT (A) lead-acid battery for his trusty radio. His load was doubled every 4 weeks as he had to add a 120 volt HT (B) battery for the return trip - and this was in 1960!

AC/DC designs although they did work off DC, the reality was that they did not work as well, if at all satisfactorily. This was because the HT supply was lower when operated from DC than it was from AC. A 240 volt AC/DC design (obviously) has an HT voltage of 240 volts when run from DC. But when run from AC, the reservoir capacitor charges to the peak voltage of 339 volts which reduces under load to somewhere around 310-320 volts. Although the vision and audio circuits would not complain too much, the deflection circuits either have to have a method of making up the loss of voltage or not bother. Many TV set makers in later years adopted the latter approach which is why many (technically) AC/DC designs are actually specified as operating from AC only. I B Wright (talk) 13:35, 14 November 2012 (UTC)

This last point is very relevant. Even the All American Five, which was designed to operate from a maximum input voltage of 120 volts actually has a B+ (as the Americans like to call it) of 160 volts (any AA5 service sheet will confirm this). This means that when run off of 120 VDC, the B+ voltage cannot exceed 117 volts (allowing for the 3 volts dropped across part of the rectifier heater and the dial light) and that the performance must be compromised to some extent (the most evident probably being the amount of audio power available).

Early valve (tube) colour TV sets were built to the AC/DC design but I note from early service sheets that the sets were specified as operating on AC only. I can only assume that the lower HT voltages (as we like to call them) that would be available would not operate some circuits as well as would be desired (the deflection circuits leap instantly to mind here). Later sets, although largely of AC/DC design, included a small transformer solely to run the CRT heaters in order to avoid cathode to heater insulation problems (making the operation resolutely AC only). These appeared initially on sets that were fitted with Mazda tubes as these had a poor history of cathode-heater breakdown. A transformer was often an after market modification to overcome such a short (and I still have quite few left which find use in power supply circuits). 86.159.159.194 (talk) 18:12, 14 November 2012 (UTC)

Early colour TV sets to the AC/DC design were more likely to be specified as AC only because the ON/OFF switch was designed for AC and not DC. A switch designed for DC is more complicated to design because it must be designed such that an arc is not struck between the contacts when switched off. This is usually achieved by a spring loaded 'snap' action separating the contacts by some minimum distance. By contrast an AC only switch only needs to separate the contacts by a small distance as any arc automatically extinguishes at the end of the half cycle (so called 'microswitch' design). Even modern switch mode power supplies can only be used on DC if the supply does not incorporate a switch. DieSwartzPunkt (talk) 12:41, 15 November 2012 (UTC)

Energy recovery in TV deflection circuit.

The boosted HT supply is obtained by recovering energy from the line output transformer during the flyback period where the magnetic field rapidly collapses. The Bush TV22 referenced from the article clearly shows the boost diode rectifying pulses from the secondary windings at the top of T4 (and two other supply voltages are derived the same way from the primary winding or an overwind from it). It would have been very difficult to recover much energy from the deflection coils themselves as they are deliberately designed to have as low an inductance as possible (commensurate with their function of producing a magnetic field). This was necessary for a rapid flyback where a current of 2-3 Amps or so had to reverse direction in 5-8 microseconds (depending on TV system). They were also designed to have as low a series resistance as possible for much the same reason. Scan coils have a minimal quantity of ferrite core being mostly vacuum cored (the tube). Even in the circuit refered to above, even if the scan coils did have any energy to recover, the series inductor L2 would have prevented much of it from reaching the booser diode. I have not come across any line deflection stage where the boost diode is connected such as to pass any flyback pulses from the scan coils.

You cannot use an enthusiast's website to support an alternative position as such websites are not acceptable as citations for articles. The error on the cited site is why (and it may be that the owner of the site failed to appreciate the important distinction between the scan coils and scan circuit). Such sites do not have the backing of a recognised authority on the subject. Otherwise, I could produce a website that claimed anything and use it to cite some dubious point.

Some Murphy TV designs even managed to eliminate the booster diode itself relying on the line output pentode to rectify the flyback pulses from the transformer's primary (where the scan coils did not come into it). Early sets of this design had a very short life for the line output pentode as its control grid was never designed to rectify large current pulses. Mazda had to produce the special 30P4MR line output pentode which was designed to handle the pulses. I B Wright (talk) 16:43, 13 November 2012 (UTC)

It is very rare to find service sheets that show the voltage waveform that appears across the line scan coils. Indeed due to the very low inductance and resistance, very little voltage actually appears, certainly not enough to rectify to produce a 700-1000 volt boost for the HT supply (the sort of value required in a valve colour TV set) or even several tens of volts for a transistor model. The Bush TV22 line deflection is indeed unusual in that it was very rare to provide additional windings for the boost HT supply. The supply was usually obtained by rectifying the pulses directly from the line output pentode's anode (hence from the transformer primary). In a typical valve colour TV set these pulses had an amplitude of around 6 kV. The load provided by the output stage meant that the actual boost was less than this. What with this boosted HT; the EHT supply; the focus supply and having to provide a couple of amps of deflection current, line output stages were worked very hard indeed. In one popular series of early colour TV sets using the BRC2000 chassis design, the stage was worked so hard that it had to be equipped with two line output transformers connected in parallel. DieSwartzPunkt (talk) 13:20, 15 November 2012 (UTC)

Section on AC and DC

Both AC and DC are adequately linked at the head of the article. The last section describing the difference between the two is therefore completely redundant. In addition, it describes several alternative techniques, but remarks that they are totally unrelated to the subject matter of the article. Historically, it may have had relevance to some unrelated material that used to be in the article. This section is now completely superfluous and irrelevant and I have thus been bold and deleted it. 86.159.159.194 (talk) 17:08, 14 November 2012 (UTC)

Excellent! I was jumped on when I orignally attempted it. 174.118.142.187 (talk) 04:52, 15 November 2012 (UTC)

It would seem that at the time you tried to delete it, the article contained material totally irrelevant to the subject of the article (switch mode supplies; universal motors etc.). Some editors obviously believed that some explanation was necessary. With the deletion of that material, the subject section acquired various disclaimers, caveats and flags stating that large parts of it were not relevant to the article as it now is, which meant that its deletion was just a matter of time. DieSwartzPunkt (talk) 12:51, 15 November 2012 (UTC)

Polarized plugs

Being the supply power was connected to the metal chassis should the polarised plugs be mentioned? Were these AC/DC sets the creator of the polarised plug? This may apply to N.America but what about Europe? I understood from electrical people from Nethelands that Europe didn't use a grounded conductor on their 220v grids. 174.118.142.187 (talk) 04:05, 16 November 2012 (UTC)

The All American Five appeared long before polarised plugs did in the US. The early sets were potentially lethal as the heads of the screws that held the chassis in place were on the exterior of the cabinet. The position was made worse because the single pole ON/OFF switch was in the wire connected to the chassis (apparently saved the cost of a solder lug). The chassis and the screw heads were live if the set was either switched on or off depending on which way the plug was inserted. Later sets did not have externally accessible parts that could potentially be live.

Several countries in Europe do not have polarised plugs and indeed some still do not have earth connections. The Netherlands, Germany and Italy cetainly are not polarised at all. French sockets accept two pin continental plugs either way round (but are polarised for plugs with earth contact). The Netherlands generally has no earth connection except in wet locations such as bathrooms. 86.159.159.194 (talk) 13:11, 16 November 2012 (UTC)

Cheater cords

Another issue for the repair techs was a "cheater cord" which could bypass the interlock usually consisting of a power cord attached to a passthrough mounted on the hardboard bck cover for the hot chassis TV sets. When the back was removed and the set auto-disconnected a "cheater cord" coud be used to do test repairs. It was usuallyan old cord from a previously scrapped receiver. 174.118.142.187 (talk) 04:05, 16 November 2012 (UTC)

In a properly equipped and run repair facility, such a cord should have been energised from an isolating transformer removing the hazard altogether (although these days an RCCD would probably have sufficed). 86.159.159.194 (talk) 13:17, 16 November 2012 (UTC)

A cheater cord was still needed. Repair shops did not use an isolation transformer in the Canadian shops I witnessed. It would be an additional cost and the chassis ground would then be floating making it more dangerous for test equiment and personnel. 174.118.142.187 (talk) 13:26, 17 November 2012 (UTC)

I assume an RCCD is a GFCI in Europeanese. I couldn't find any description for the acronym. 174.118.142.187 (talk) 13:30, 17 November 2012 (UTC)

A typo. I thought I had typed 'RCD'. I even previewed it before I saved it and still missed it. 86.159.159.194 (talk) 18:23, 17 November 2012 (UTC)

Thanks! New term for me. 174.118.142.187 (talk) 01:41, 20 November 2012 (UTC)

This article isn't going to work this way! American vs European

We appear to have two trains of thought involved in this article. We have the North American version and the European version of history and circuitry and they will not agree as different reasons and history happened.

• In N.America AC/DC sets were created for the lack of transformer usage for economic reasons. DC didn't exist when these sets did and was never a reason or promoted. DC woud not produce a high enough voltage to run many of the tube B+ stages and would have been only .707 of the plate voltage using AC. Hard to design circuits for that wide of a range without circuit changes. The metal chassis was grounded via polarised plugs and no ground pin was available in most home recepticals.
• In Europe (I have no personal knowledge) AC/DC sets may have been actually created for the usage on both mains voltages. 220v was high enough to run many of the higher voltages needed for the B++ plate supplies needed. I have no idea what voltage level of DC was distributed to the homes. If I read correctly some had dropping resistances to bring voltages down inside some equipment. I conclude DC portability was a selling feature of EU equipment. In mains supplies home had no grounded conductor (the voltages floated to earth), in some or maybe all locations and therefore the chassis had no ground unless a separate earth wire was brought via a three conductor cord and plug. I don't believe EU utilized an earh/ground system in homes.

In short we coud be talking about two completely different concepts, circuit styles and reasons for existence and the article will always be a mess and arguments will ensue forever unless we admit and find a way to separate these differences. Comments? Techniques and methods? 174.118.142.187 (talk) 00:47, 17 November 2012 (UTC)

Not really. The AC/DC technique was devised with the birth of the All American Five radio receiver in the USA. It was devised as part of the design goal of that set, which was to make it as cheap as was possible to manufacture (all other considerations were secondary - including safety!). That it operated on DC as well as AC was nothing more than a convenient side effect and exploited as a marketable feature. The design was not independantly created in Europe but simply copied once the AA5 designers had shown the way.

AFAIAA, there has been no floating mains supply anywhere in Europe (but I'm sure someone will point one out). Historically, the neutral conductor was earthed (grounded) at the substation, but not necessarily anywhere else, thus the neutral was not guaranteed to be at earth potential. These days (at least in the UK) the neutral conductor is bonded to the earth conductor at every point where the supply enters a building. Also in the UK, a DC mains supply was generally distributed at 200 volts DC. However, as it was generated as a (+200)-0-(-200) volt system (with the centre '0' point earthed at the power station), the live conductor, in a two wire location, could either be 200 volts positive or negative with respect to the earthed conductor. The nearest any present system gets to this scheme is a unique system that was trialled in part of West London where the supply really is 230 volts AC, but it is distributed as 115-0-115 volts. This was presumably a safety idea, but the system still survives. The idea also lives on in professional portable tools which are usually rated to run from 115 volts from a transformer with an earthed centre tapped secondary (i.e. 55-0-55 volts).

Historically, the loads that were connected to DC mains were not polarity sensitive (lights; heaters; cookers; DC motors etc.) so there was no need to specifically identify the actual polarity. A radio designed for DC mains was probably the first available appliance that was polarity sensitive. If it didn't work, you simply plugged it in the other way around (plugs were non polarised in the early DC days - and indeed for AC). As stated, most users would be unaware of the actual polarity of their supply and the wire colours gave no clue as the grounded conductor was coloured black and the live conductor, red regardles of its actual polarity. Only in installations where all three conductors were available was the polarity of the live conductors identified (and I cannot find the colours used). — Preceding unsigned comment added by 86.159.159.194 (talk) 18:56, 17 November 2012 (UTC)

Without any references I totally agree with your first paragraph and this is why I started the Eu vs. Am differences argument. Cripes we changes our systems from 25Hz to 60Hz in the early 50s and nobody reports any DC distribution when these sets were popular. At a few hundred km. from the nearest generating stations I doubt a few hundred volt DC transmission line went that far. Perhaps it was happening in Eu with less loading but not in Canada. I also doubt the DC came locally from battery systems.

I would be interseted in where these Eu 220v systems were grounded. Was it a 110v centre tap neutral ground and not distributed? I worked with Dutch grid system protection techs and they talked about lightning jumping across the receptacle pins, as kids in Holland. I understood the distribution wasn't grounded at all into homes.

I know some tube audio equipment would hum badly and the cure was to reverse the AC plug in the receptacle. Many of the floating chassis sets had a small cap from one of both lines to the metal chassis. Yuk! 174.118.142.187 (talk) 01:06, 19 November 2012 (UTC)

I would be very surprised if any distribution system was not grounded somewhere (but someone will, no doubt, point out one that wasn't). The lack of a ground would risk the system acquiring voltages well above the distribution value. Even if I hire a (3 phase) generator for some public event, the casing usually has a prominent notice warning that the earth terminal (and hence the neutral) must be grounded (using the metal rod provided with it). I know little of European systems in general, but the EU is in the process of harmonising many of the requirements. For distribution purposes, there is much commonality to start with so harmonisation seems to be confined to things like tweaking individual requirements, wire colours and what voltage we describe the system as.

AC/DC equipment would have the tube heaters wired in a specific order, usually placing the sensitive tuner and R.F. tubes at the chassis end of the chain and the less sensitive tubes such as audio output and rectifier at the other end. If the chassis was live then the sensitive tubes would have an electrostatic feed of 50 or 60 Hz into the cathode. Turning the plug round would, at least in theory, fix this. Early AC/DC sets had one side of the mains directly connected to the chassis. Later All American Five sets (and most likely US TV sets) kept the mains connections separate from the chassis, but as you note, a capacitor would establish the chassis as a ground - at least for R.F. At least in the UK, the practice of directly connecting one side of the mains supply directly to the chassis persisted in AC/DC television and radio sets. I believe that it was the American Underwiter's Laboratory that insisted that the direct connection was removed in US sold equipment.

Whilst not being able to speak for other countries, DC distribution (where it had existed) had all but disappeared in the UK before the AC/DC design appeared shortly after 1945. Prior to this all mains operated TV sets had mains transformers having been manufactured for just three years before war broke out. Radio sets were usually offered in AC only but there were a few DC only models available in the 1930's for those few areas where DC still existed. There may have still been some outlying potential DC market by 1945, but it would have been nowhere near large enough for the design to be adopted on that score alone. DieSwartzPunkt (talk) 12:38, 20 November 2012 (UTC)

Obsolesence statement

DC-only equipment was usually a little cheaper than AC/DC, but became obsolete as AC power became dominant, solid state circuitry requiring less power evolved making transformer size requirements smaller, and safer designs were produced.

The clauses added from "solid state circuitry" was added to expand/list the reasons AC/DC equipment became obsolete. One editor wants to break the sentence into two sentences that appear unrelated to each other and presents some shock value to the reader. Another reader wants it removed after being broken as it then borders on nonsense and I agree somewhat. This needs to be discussed and some agreed result achieved, here. Editwarring is happening and heads could roll if an admin happens by. From other articles, I perceive when editwarring happens, the articles get very formal and only with references, statements will survive or be permitted. This whole article looks mostly unsubstantiated and could be removed with that rule. Where are we going with this? 174.118.142.187 (talk) 02:58, 23 November 2012 (UTC)

Your quoted section is actually incorrect. The AC/DC design did not become obsolete when DC mains systems disappeared. DC operation was never a design goal and this fact is currently only implied in the article (it did state it, but has been lost in the edit war). The AC/DC design persisted long into the era where AC mains was predominant, particularly in television design where there were large numbers of valves (vacuum tubes). Valves required comparatively large amounts of power for their heaters. For example a small signal pentode which consumed around 20 or so milliwatts from its high voltage supply required 2 watts to heat up the cathode. A 240 volt television set with its valves and CRT required 72 watts just to heat the valves (including the power lost in the ballast resistor). Thus the potential cost saving of not having to provide a mains transformer was very attractive to set makers. The introduction of solid state circuitry eliminated the valves and their heater requirements, and the (now much smaller) transformer made a brief reappearance. Developments in thyristor power supplies and later switch mode supplies have eliminated it again, but that is a whole different article.

As for an edit war, you are correct. The article has been recently mauled by an established and tendentious edit warrior, Wtshymanski who somehow seems to believe that he owns Wikipedia. The admins have so far failed to take much in the way of action. You might care to read this to see what I am talking about. The fact that you are an IP address editor does not help because Wtshymanski does not believe that such editors should be allowed to edit 'his' encyclopedia. Stick with it, you are' welcome. DieSwartzPunkt (talk) 17:56, 23 November 2012 (UTC)

Article existence?

Perhaps the whole article needs to be removed. It's a mess and has been tainted badly with the DC usage statements that seem to only be imagination. We already have an article on the All American Five but it doesn't cover the many transformerless TV set designs I have witneessed. What equipment are we actually discussing? How is the article title even related? This article looks like it should be renamed "Transformerless receivers" 174.118.142.187 (talk) 02:58, 23 November 2012 (UTC)

The so called AC/DC design was an important milestone in the development of low cost radio and television designs. That fact alone more than justifies the article's existence. I'm not sure exactly what you mean by, "... tainted badly with the DC usage statements that seem to only be imagination", though some of the article's claims are incorrect. It has become quite scrappy in places (particularly the Transformer section which is needlessly repetitive). I note that one paragraph has recently had a rewrite. If you feel that the article's wording can be improved, then go ahead, be bold and have a go. DieSwartzPunkt (talk) 17:25, 23 November 2012 (UTC)

The "tainted badly" retort was agreeing with your many statements about the design not related to DC distribution. IOW the article contains many fantasies using this reason. AFAIC these designs would never run on DC anyway for many historical timing and electrical reasons. This comes back to "Why does this article even exist under this name" I believe "transformerless" needs to be in the artlce title instead of any DC mention. Does anybody have an references to these schematics or manufacturer's brag on these units? I know techs referred to them as AC/DC but it may have just been a nickname.174.118.142.187 (talk) 02:22, 10 December 2012 (UTC)

This type of design is known almost universally by radio and television engineers as "AC/DC" and as such that would be the correct article title. I cannot see any objection to 'transformerless power supply' and 'transformerless design' being set up as redirects (though the latter could be confused with other areas where transformers are designed out). I B Wright (talk) 14:28, 17 March 2013 (UTC)

[undo] button

There exist seldom situations when pushing to [undo] link is an appropriate action. But if one removes numerous tweaks because he baldly disagrees with changes in only one phrase, then it is nothing but a content disruption. Incnis Mrsi (talk) 18:21, 28 February 2013 (UTC)

If one makes edit comments that don't describe the scope of edits, one should be preprared to find one's edits reverted when the first screenful shows a conspicuous degradation of the text. Hyphens and non-break spaces, Easter Egg links, arch in-line editorial comments, and changing the capitalization in footnotes, are unfortunately all swept away. --Wtshymanski (talk) 19:14, 28 February 2013 (UTC)

Your persistent negative bias towards most changes by other editors may, eventually, pave your way out of English Wikipedia. But now, be only prepared to have any your action, which looks clearly destructive to somebody’s good-faith edit (possibly a third party), be reduced with my [rollback]. Incnis Mrsi (talk) 19:53, 28 February 2013 (UTC)

BTW, the only my invention here which can be characterized as an Easter Egg link is [[galvanic isolation|separate transformer windings]]. Possibly, it was not a good choice, but I was not willing to make textual changes in a paragraph where I am not an expert. Just fix it. Incnis Mrsi (talk) 20:06, 28 February 2013 (UTC)

Not willing to make textual changes, but willing to hide eggs? If its relevant, it can be explained in the text; if you're not sure its relevant, piping it doesn't make it less uncertain. "Just fix it"? Do you really want to say it that way? I review about 80-100 changes to articles on my watch list every day and only rv v 8-10 of them, so it's mathematically not true that I have a negative bias toward most changes. But I can't blow the driveway without getting some snow in my face....--Wtshymanski (talk) 20:51, 28 February 2013 (UTC)

The article witters on about the dangers of directly connecting the radio to the line, and yet we feel we need a tag that asks for this to be confirmed? The dubious editor could consult 30 or 40 of the many hot chassis schematics on the Web and observe that one pole of the plug is directly connected, yeah verily, even unto one terminal of the electrolytic filter capacitor - at least in those hot-chassis sets using half-wave rectifiers. --Wtshymanski (talk) 14:42, 1 March 2013 (UTC)

While many would agree with you, Wikipedia nevertheless requires references for any material likely to be challenged. The addition of the offending tag means that it has been challenged. However, there is an essay that suggests that references are not required for the blindingly obvious. See WP:BLUE for what must rate as common sense. I would say that this falls into that category. 86.166.71.0 (talk) 15:27, 2 March 2013 (UTC)

A rectifier and a filter are connected directly to the mains

What means the word “filter” in this context? A filter of what? If it is a reservoir capacitor (an obvious association to "rectifier"), then it cannot be “connected directly to the mains”. Incnis Mrsi (talk) 15:11, 1 March 2013 (UTC)

I suggest looking at the schematic of any "All American five"-type radio, when you will notice a direct connection between one side of the filter cap and the line. --Wtshymanski (talk) 21:21, 1 March 2013 (UTC)

In a linear power supply circuit, the first capacitor after the rectifier is usually referred to as 'the reservoir capacitor' but also gets refered to as a 'filter capacitor'. The second capacitor, usually placed after a resistor (or more rarely these days a choke) is usually referred to as 'the filter capacitor' because together with the resistor or choke it forms a low pass filter which readily passes the DC current, but attenuates the AC ripple superimposed upon it. In the All American Five, one of the features of its design was indeed that both the rectifier, reservoir capacitor and filter capacitor were directly connected to the incoming mains supply. For a simplified diagram of the AA5's power supply see here (about half way down). 86.166.71.0 (talk) 15:15, 2 March 2013 (UTC)

“ The plate is bypassed to ground by a .005 mike cap ”

is not a filter capacitor, connected directly to the mains. I do not see such direct connection at http://www.angelfire.com/electronic/funwithtubes/images/AA5-1.gif (even if to neglect the switch), do you see it? Incnis Mrsi (talk) 17:33, 2 March 2013 (UTC)

But there's a solid black line running from the common terminal of the dual electrolytic (labelled "Dual Capacitor 40-40 @150WVDC"), with a chassis ground symbol, running to the switch, then from the switch to the plug! A terrible fragmentary schematic, there's tons of more complete ones on the Web, but even this fragment suffices to show the direct connection. It's a little atypical because often the - side of the power supply was not wired directly to the chassis but instead connected to the chassis through a parallel RC network (to limit the current available if anyone did touch the "hot chassis")...however, given the fragmentary nature of this schematic, maybe they just used a "chassis ground" symbol when they meant to say "circuit common". Did you somehow get a bad copy of the .JPG, do you perhaps have some other reason you can't read schematics? --Wtshymanski (talk) 20:10, 2 March 2013 (UTC)

What do you try to say about the dual electrolytic? It is connected to (output of) the rectifier, not “directly to the mains”. You may say that it has one common pole with the mains switch, but, since it is only one, this is not a situation which can be described as a “filter connected directly to the mains”, as I understand this. Incnis Mrsi (talk) 20:41, 2 March 2013 (UTC)

Your unique perspective challenges and refreshes us all. --Wtshymanski (talk) 22:59, 2 March 2013 (UTC)

Only one side of the filter capacitor needs to be connected for a 'direct connection' to be established. If the mains plug is inserted such that the chassis of the radio is connected to the live mains conductor, then we can go one stage further and say that the filter capacitor is connected directly to the live mains conductor. To draw an allusion, if you take the wires from your local mains supply, lick one finger and place it in contact with just the live wire, you will have little doubt that you have established a direct connection with the mains supply (Health and safety notice: Don't try this at home folks!)

The 0.005 MFD capacitor that you refer to serves to decouple the centre tap of the rectifier heater as this is the reference point for all RF signals within the set. It is not a filter capacitor as such and certainly nothing to do with fitering ripple from the power supply. However, like the power supply filter capacitors is is directly connected to the incoming mains supply for exactly the same reasons. 86.166.71.0 (talk) 16:25, 3 March 2013 (UTC)

The fragmentary diagram is no so atypical because it does represent fairly accurately the power circuitry of early type All American Five radios. Later radios did have the chassis itself isolated from what you describe as 'circuit common' by an RC network designed to provide some isolation from the 60 Hz mains supply but not the RF signals the set was designed to receive.

Your trademark sarcastic edit summary is wholly out of place because it is quite possible that Incnis Mrsi does not understand the concepts being discussed. As usual you are not assuming the required good faith that Wikipedia demands. 86.166.71.0 (talk) 16:39, 3 March 2013 (UTC)

Scope of article

This article was written to describe a significant development in the history of the power supply in domestic vacuum tube based radio, and later, television receivers. Its scope is even stated in the article lede. This type of power supply design is known almost universally among radio and television engineers as the 'AC/DC' design. As stated in the article, its goal was to eliminate the large and expensive mains transformer. A design side effect was that the resultant receiver would work from a DC supply as well as an AC. The tally plate on these receiver confirmed that the supply could be AC or DC.

A couple of editors have attempted to add a link to the switch mode power supply (SMPSU) article as a 'see also'. However, SMPSUs are out of scope for this article because they are not transformerless and furthermore, there will be supporting reference problem because SMPSUs do not usually state on their tally plate that they will run from DC. There is also the issue that the ability to run from DC is not universal and without a clue on the tally plate, it is impossible to determine which will and which won't from a casual examination. Similarly, the Universal motor 'see also' is also out of scope, because although transformerless (as in never having featured one), it nevertheless has nothing whatsoever to do with vacuum tube equipment.

Four criteria have to be met for any SMPSU to work from DC.

1. The input circuit must be a bridge rectifier, not a voltage doubler circuit. Many supplies, particularly in 100-120 volt areas have the latter. No voltage doubler works from DC.
2. The supply must not be fitted with a mains switch. The switches usually encountered are not rated for DC. Switches for DC require a specialised design to extinguish any arc struck as the switch contacts are separated.
3. The input rectifier elements must be rated at twice the current that is required for AC operation. Few manufacturers are likely to oblige on cost grounds. All the input current on DC flows through two rectifiers, whereas on AC it is shared around all four. On DC the two rectifiers that do conduct must dissipate twice as much heat. Having said that some rectifiers will cope because they come in fixed current ratings and some may be adequately rated because the next size down was too small.
4. For normal operation, switch mode supplies require a higher DC voltage than they do AC. This is to do with the peak voltage of AC being higher than the DC voltage - a 240 volt AC supply has to be run from around 330 volts DC. This is because the reservoir capacitor attempts to charge to the peak AC voltage (of 339 volts for a 240 volt RMS supply). The power supply load lowers the actual reservoir voltage.

But the real question is: does the scope of the article need to be expanded to cover all equipment that can run from AC or DC? It will become a very long article because there would be a need to include incandescent lamps; universal motors; fluorescent lamps; compact fluorescent lamps; electric cookers; electric toasters; electric fires (but not fan heaters); curling tongs etc. etc. etc. I personally think not as the article was scoped for exactly what it was intended to describe. But I throw the floor open. I B Wright (talk) 19:25, 28 April 2013 (UTC)

Fluorescent lamps are not inherently AC/DC as the ballast is often a series inductor, which would act as just a straight wire at DC. Universal motors are AC/DC and I have no idea why you keep removing them. The text already mentions that incandescent bulbs and heaters don't care about line frequency; all you've done is pointlessly mention heaters four times under slightly different wording (cooker, toaster, tongs, fires) as a strawperson argument. They're mentioned once, leave it at that. SMPS are regulated power supplies, so you might be overemphasising the peak-vs-RMS voltage issue just a wee bit. The voltage-doubler, if present, is normally used only for 120V and turned off when using the same dual-voltage supply on 240V. The input rectifiers are always sized for the peak voltage and current (plus a margin), not the average as it takes only brief out-of-specification operation to damage semiconductors. Mechanical hard power switches are also becoming less common on SMPS; laptop power supplies are always on, ATX PC's are momentary soft switch, TV's and monitors don't fully shut down as they carry standby power until "awakened" by remote control.

The difference between "hot chassis" (where the rectified line is used directly, tying one side of the line to the chassis) and SMPS (where the rectified line is inverted back to a higher-frequency for a lightweight transformer) is worth mentioning as there is a huge distinction in electrical safety. The original use of "DC" to refer to Edison-style distribution of DC at line voltage is very obsolete, so the context should be explained (by the 1970's, "DC" was more likely to be battery or vehicle power - a quite different beast).

Comments like "will operate from DC but are also not referred to 'AC/DC' and the rating plate never mentions DC anyway" in the article body are opinions, not facts. This is not an opinion/editorial page. Statements of opinion should be removed from the text. K7L (talk) 02:32, 30 April 2013 (UTC)

Fluorescent tubes are inherently AC or DC. That the ballast is often chosen to be a series inductor, means that the assembly will only work correctly from AC. But there is nothing that says that the ballast has to be an inductor. It can be a resistor in which case DC operation is quite posible. In the 1960's fluorescent fittings were available that used a 170 volt 60 watt filament lamp as balast (designed to run from a 240 volt AC supply). To operate reliably from a DC supply, a means has to be provided to reverse the polarity to the tube at each start as indeed was the case in very early DC fittings.

Input rectifier diodes on switch mode supplies are rated for the peak voltage, but only half the average current (plus, as you say, a margin) as they only conduct on each half cycle (or in practice, less than that). The peak current rating for a rectifier is usually much greater than the average rating (for example a BYX38 is rated If(av)=2.5 amp but If(max)=38 Amps). When run from DC, two of the rectifier diodes have to conduct the full DC current constantly, thus the average current through them is near enough double what it would be on AC. The other two are effectively redundant.

But in spite of that, the scope of the article is still transformerless vacuum tube power supplies (the AC/DC design), with which universal motors has no connection whatsoever. SMPSUs don't either. That they are not referred to as 'AC/DC' supplies is not an opinion but a fact. I challenge you to find any reference where they are described as 'AC/DC'. In fact, to be brutal, the term 'switch mode power supply', is a far more encompassing term than the type of power supplies that you are discussing. The type of supply for your PC or laptop is just a subset of SMPSUs (actually flyback SMPSUs). An SMPSU can have a mains transformer and much of the other paraphernalia of a linear power supply (just the linear regulator is replaced by a switch mode regulator). These definately will not work from DC. Such supplies are generally only encountered these days in large laboratory power supplies (there is a 0-70 volt, 200 Amp one on a trolley not far from my bench - weighs in at around quarter of a tonne, mostly the transformer) though they used to be far more common in smaller sizes.

You have not provided any justification for the scope of the article to be widened. I B Wright (talk) 15:37, 3 May 2013 (UTC)

Ask any engineer old enough to remember the good old days of vacuum tubes what an AC/DC power supply is and he will instantly think of transformerless vacuum tube radio and television sets. He will not think of modern switch mode supplies. Ask any engineer not old enough to remember vacuum tubes and he will not have a clue what you are talking about. Again, switch mode supplies will not leap to mind, because they are not known at all by anyone as AC/DC supplies and most engineers are actually unaware that they will operate from DC (though will appreciate it when it is pointed out). The rating on such supplies invariably says something like "240V AC 50/60 Hz" but only because that is the frequency range of mains supplies these days. The rating actually hides the fact that they will operate at frequencies well outside of that range. We frequently operate standard switch mode supplies at 400 Hz without problem.

In any case, the ability of some switch mode supplies to operate from DC is entirely moot as DC mains supplies have been somewhat hard to find since such supplies were developed. 86.145.244.180 (talk) 10:47, 4 May 2013 (UTC)