Talk:All American Five

Grammar

If you are going to correct spelling and grammar, then make sure you know the rules to start with.

The correct version of "1930's" (a correct plural) was replaced with "1930s". There are a few examples where the plural has an apostrophie - 1930's (as in the decade 1930 -1939) is one of them.

This plural has been 'corrected' wrongly twice.

And now wrongly corrected a third time.

The page it links to is wrong.

Rightly or wrongly, Wiki doesn't use apostrophes with years.

Atlant 23:16, 11 May 2006 (UTC)

It's wrong - where does it state this? If satisfactory answer not received, I will revert as most of them is in those parts of the article that I wrote, as I don't want a reputation for not knowing the correct way to use an apostrophie. —The preceding unsigned comment was added by 86.140.80.34 (talk • contribs) .

It says it at Wikipedia:Manual of Style (dates and numbers)#Incorrect date formats:

Do not use an apostrophe to indicate a decade:

Incorrect: 1970's

Correct: 1970s

Then the style guide is wrong. In English, the decade is correctly written with an apostophie. I assume the style guide was written by an American. Americans have not used English for over 2 centuries.

Atlant 20:20, 29 May 2006 (UTC)

About the chassis being "hot"

The article refers to the Underwriter's Laboratories (UL) requiring a 100k resistor between the mains and chassis. Although I can find several improvements demanded of the UL, mainly to do with proximity of high voltages with low, I can find no reference to a 100k resistor, nor indeed, any schematic that shows one. Such a resistor would be pointless in and AC/DC design as it would drop almost the entire mains voltage across it.

All the AC/DC design radios (and televisions) that I have serviced have had the chassis very much live if the plug was inserted the wrong way round. This practice prevailed towards the end of the 20th century until Switch Mode Power supplies rendered the design obsolete.

—The preceding unsigned comment was added by 86.137.52.221 (talk • contribs) .

Every AC/DC radio I worked on had an isolation resistor between the power cord (signal "ground") and chassis. It is clearly shown on their schematic. The power cord was connected to the power supply section at Power "hot" and signal "ground". If plugged in backwards then Power "hot" was neutral and signal "ground" was hot, but the chassis was not hot. None of the circuitry used chassis as a "ground". You got a shock, but it never felt like more than a "tingle".

Right now I don't recall the exact value of the isolation resistor, but it was in the Megohm range. See typical schematic (it is the 220Meg resistor on the left with a 0.1μF cap across it). I will change the value in the article. -- RTC 01:50, 15 February 2006 (UTC

Response:

I had not seen this arrangement before (at least not in this location). 200M seems a better choice of resistor than 100k as it will reduce the current below the threshold of sensation. Exactly what the objective was is not clear. The internal live parts can easily be isolated from the user as they subsequently were. However, the circuitry is nevertheless still live to service personnel even when the set is switched off.

As I said, I have not encountered this arrangement, but I am in the UK. Standard practice here was to operate an AC/DC radio or television from an isolating transformer during servicing, thereby eliminating the danger entirely.

It is interesting to note that this particular UL requirement seems to predate their insistence on rearranging the tube pin-out to move the plate pin away from the heater pins. Quite why they did this is also unclear as the plate voltage is not high by any standard. Safety organisation do come up with some strange directives sometimes.

When I first entered the value of 100K it was from (bad) memory; and I intended to check some schematics and update it with the correct value. However I got busy with other things and didn't get back to it before you did. Luckily I found a schematic on the net that showed it. However I don't recall there being a standard value for the resistor, different sets and different manufacturers used different values, but it had to limit the current to a "safe" value if a person touching hard ground touched the chassis.

The primary objective of the resistor was to prevent repair men from electrocuting themselves by accidentally touching the chassis while working on the radio. In any radio it was possible to get hurt if you touched the wrong thing in the live circuits, but chassis should always be "safe" (even if circuit "ground" isn't). It also made it "safe" if you accidentally touched a hot circuit and the chassis (as long a you were not already grounded elsewhere). One extra resistor and a bypass capaacitor for it was cheap safety – and as you say these sets were cheap.

I never used an isolation transformer. Usually just plugged it in, kept one hand in my pocket and ran a finger against the chassis. If I got a "tingle" I reversed the plug and tried again. I always tried to work on radios and TVs with one hand in my pocket when they were plugged in. -- RTC 20:59, 16 February 2006 (UTC)

I finally dug out my old books. I found schematics showing isolated chassis (also called floating chassis) circuits that had resistors as small as 22K through as large as 330M; even ones that used no resistor, just the 0.1µF or 0.2µF ground bypass capacitor. 220K and 330K were very common values. Some schematics in the book did have a true hot chassis (but I've never actually seen or worked on one myself).

So it turns out my memory wasn't all that bad after all. -- RTC 20:38, 4 March 2006 (UTC)

I note that a contributer modified the article to state that the tube heater chain would limit the current to someone who contacted the chassis. I incorrectly calculated in my head that the resistance would be around 150 ohms or so, which would not provide much limitation in such circumsances. However, consulting tube data, I find that the resistance is much lower at around 60 ohms for the entire heater chain. It rises to 800 ohms when the heaters all reach their working temperature.

Power supply

I jumped on a change that was made today, as it tried to simpliphy but in the process made the ideas less clear.

1) the filament/heater tap is an option for the dial light, not all radios had them, and a missing burned out light probaly did not have much effect on reliability. It might cause a problem if the curent draw was already high. Many units did not have a dial lamp.

Actually, a burned out dial light had a huge effect on reliability as it caused that section of the heater to carry the current that was not diverted through the dial light. This in turn heated the cathode to a temperature far higher that it was designed for and more or less stripped off the oxide coating. The rectifier tube could literally fail after a few hours of such use. 20.133.0.14 14:15, 5 September 2006 (UTC)

A 35W4 or a 35Z5 has a heater rating of 150ma. If you put a dial lamp that nominaly draws 100ma, the section of the tube heater taps will see LESS than the normal curent, if the dial lamp pops it will see "normal curent"..NOW if their is say a leaky filter (you use the term smoothing) that incresed the draw, both will pop. Their is probaly only 50ma of dc draw on a heathy radio.

You have overlooked the fact that the B+ supply current is routed via the part of the heater that has the dial light connected across it. The Dial light current rating was designed to be the same as the B+ current. The failure of the dial light caused the heater current plus the B+ current to be routed through that part of the heater. The B+ current can be observd in a real radio. At switch on, the heaters are cold and pass a large current. The dial light light to more or less full brightness, but as the heaters warm up and the current falls, the dial light dims considerably. As the rectifier and the other tubes start to conduct, the B+ current starts to flow through the dial light and the parallel heater section and the light resumes to full brightness. 86.132.200.242 17:36, 13 July 2007 (UTC)

when tubes are made, they are run at 200% of heater rating to activate the cathodes, so any slight variation will have little effect.

But that is only while the cathodes are being activated. It is a process that has to be carefully monitored because once the cathode is activated it will destroy itself very soon after. Regardless of this, it is a matter of record that a failed dial light would cause the rectifier tube to fail far quicker than it would normally do so. 86.132.200.242 17:36, 13 July 2007 (UTC)

cmacd 14:54, 5 September 2006 (UTC)

2) the norm was to use the tap as a fuse, thus the plate curent went through that section and the Dial lamp. You could actually see the lamp brighten as the radio started to play. If a short happened, the lamp filament would blow at the same time as the tube heater.

I have not been able to find any reference to this part of the circuit acting as a fuse.

Look in any RCA tube manual, the circut is clearly described in every edition from RC-12 to RC-25

cmacd 14:54, 5 September 2006 (UTC)

Tube rectifier circuits are rarely fitted with fuses, and even if they were, the relatively high resistance of the rectifier tube itself, would render the fuse pretty ineffective.

There is always SOMTHING that will act as a fuse, even if it is the power transformer. :) Many appliances (and vehicles)use a length of small guage wire as a fuse. cmacd 14:54, 5 September 2006 (UTC)

I have never seen a fuse in the plate circuits of small tube rectifier sytems (I have in larger systems). Every domestic radio or whatever that I have serviced with a short on the power supply, the inherent tube resistance has limited the current (the glowing plates are a bit of a give away though). 86.132.200.242 17:36, 13 July 2007 (UTC)

It is this resistance that severely limits the size of the reservoir capacitor. Too large a capacitor and the surge currents can damage the cathode. 20.133.0.14 14:15, 5 September 2006 (UTC)

Their is an optmum size for the filter cap, and yes too big a capaitor will overdraw the circuit and blow the fuse. in the 1930 the cap was 8 MFD, and later ones got up to 80.cmacd 14:54, 5 September 2006 (UTC)

3 Edison wired NY and other areas with DC power, and it was the 50's before everyone had ac. The Niagra falls area had 25 Cycle power until the war. A transformer set would not work in a dc area, and a 25 cycle set would need a special transformer.

So what? Although the All American Five would operate on DC (as long as you put the plug in the right way round), as the article states, this was a side effect not a design objective. A different version of the set would probably have been required for a 25 Hz supply as larger reservoir and smoothing capacitors would be required. The former would have been limited in size by the rectifier tube characteristics. 20.133.0.14 14:15, 5 September 2006 (UTC)

The use of a larger second stage filter can also be considered, as well as the value of the resistor between the two (or more) caps, (where the ripple is dropped)

cmacd 14:54, 5 September 2006 (UTC)

Atwater Kent

Note: Atwater-Kent did not go bankrupt because they refused to make an AC/DC set. Atwater-Kent refused to unionize.Dfoley51 00:30, 7 October 2006 (UTC) RESPONSE: Not true. Unionization issues may have been one added reason for the owner's decision to get out of the radio business, but did NOT cause Atwater Kent's precipitous fall in market share as a radio manufacturer. Atwater Kent was the #1 manufacturer of radios in the country from 1926 through 1929. In 1929 they were producing almost a million receivers a year. However, during the Depression, where the cost of the average purchased radio dropped 75% or more, it was Atwater-Kent's refusal to produce cheap AAF table radio designs and concentrate on upper-end console models that first caused its business troubles. By 1931 the engineering department had already closed, meaning that the company was simply mass-producing existing designs until they ran out of steam. Sales continued in a downward spiral. In the last years the company's workforce was only 800 employees (down from a high of 12,000!), mostly on-call workers, and unionizing would have resulted in little leverage anyway. By 1936 Arthur Atwater Kent was tired of the radio business, and made the decision to close the factory for good.. -AK 6 MAR 2007

I can buy that version, I can't imagine AK even CONSIDERING building less than a high end unit. The old version made it sound like he was forced to pick between making a stock RCA design or going out of business. I can imagine more than a few makers were caught by the combination of the depression, and the technological change represented by the AA5. cmacd 12:49, 22 March 2007 (UTC)

DC voltage

"The radio used a simple half wave rectifier to produce about 160-170 volts of plate voltage."

This would be true for a perfect rectifier fed 120VAC (120VAC*1.414= 169VDC).

With low-cost vacuum rectifiers like 35Z5, the actual voltage was more like 125VDC. See 35Z5 data-sheet: http://www.mif.pg.gda.pl/homepages/frank/sheets/127/3/35Z5GT.pdf which shows 122V-127V at 60mA current

You need to find out what data sheets are trying to tell you. The 125 volts quoted is merely the plate voltage at which those characteristics apply. It also quotes them at 235 volts, but I would not even try to use that as evience that the half wave rectifier produced 235 volts.

See also 50L6 data: http://www.mif.pg.gda.pl/homepages/frank/sheets/127/5/50L6GT.pdf which shows operation at 110V across the tube (add ~7V bias and ~7V drop in output transformer= 125VDC).

Yes, 50L6 is allowed higher voltages, but never got it with AC/DC construction and vacuum rectifiers; and later "5-tube" tube-sets often used a 150V-max output tube.

The low voltage limited such designs to 1 or 2 Watts power.

PRR 68.239.136.129 08:22, 11 February 2007 (UTC)

All the All American Five service sheets and diagrams that I have seen all refer to the B+ voltage being around 160-170 volts. Most of the cited links do as well.

86.132.200.242 17:36, 13 July 2007 (UTC)