Help with a Admiral Portable TV ,1950's

[DavGoodlin]

Transformer-less TV sets have a few more precautions than the 1940's radios did.
A polarized plug (and interlock) was usually found on a 1950's TV, but not a plastic-case radio of the same vintage. Many of these radios have the metal knob-shafts insulated from the chassis via a capacitor and no other exposed metal parts.

No fuse or breaker will clear at the 30 milliamps that it takes to electrocute.

Ground fault circuit interrupter GFCI receptacles are always a good idea for any work bench and are code requirement for basements, garages, outdoors, kitchens, bathrooms and within 6 feet of a sink. The cost is about $12 and can save your life.

I use a neon tester to verify if the shorter slot of a receptacle is connected to hot/line side/black wire and the wider slot is neutral/white (the same as ground).

[Jeffhs]

Anyone who would use an AC-DC radio in a bathroom is taking a terrible risk. I did not realize fuses and circuit breakers will not open or trip, respectively, at just 30 milliamps; it would have saved many more lives if they had been designed to open the circuit at this current level. I can understand why fuses cannot blow fast enough to prevent electrocution; however, would it be possible to make a circuit breaker sensitive enough to trip at 30 milliamps or less? Of course, a sure-fire solution would be to get people to stop using AC-DC radios in bathrooms, but some people just don't get it that they are putting their lives at risk doing this. This kind of hazard is probably outdated today as far as AC-DC radios go (most people trashed their AC-DC sets years ago when transistor sets became popular or never owned an AC-DC one), but it is still a risk with appliances. As I mentioned in another post, a baby was killed decades ago when a toaster fell into the kitchen sink where the child was being bathed by its mother, and there are probably countless other accounts of such fatal accidents as well.

This is why today's line-powered radios, televisions, and appliances are now equipped, by federal law, with polarized AC cords, and why, as DavGoodlin mentioned, the National Electrical Code now requires GFCI (ground fault circuit interrupter) equipped outlets in damp locations such as kitchen sinks, bathrooms, basements, laundry areas and the like.

BTW, the "hot chassis" design did not disappear with the advent of all-solid-state radios and televisions. I have a late-model (1999-2000) RCA 19" color TV which has a hot chassis and, of course, a polarized line cord. One major hazard with this design is if, for any reason, the speaker leads are shorted, to each other or to ground, the television will be seriously and permanently damaged.

I don't know, however, if the same thing can happen with hot-chassis tube-powered radios or televisions if the speaker(s) connections is/are shorted. Tube-powered AC-DC radios may be more forgiving of this type of short, although I would think a solid-state AC operated radio would be destroyed in an instant if the speaker(s) was/were shorted to each other or to ground. The former (speaker leads shorting to each other) seems to me to be more likely to permanently and severely damage the radio, making it instant junk. I also think that if the speaker(s) were somehow shorted directly to ground, there would of course be no sound and the house fuse or circuit breaker might open or trip, respectively; there should not be any permanent damage done to the device in which the speakers are installed and used.

[peverett]

The Admiral that started this thread does not have a polarized plug-I just checked mine. This set depends on the insulators. This is also true of a late 1950s, portable series string RCA that I am restoring now. It also does not have a polarized plug, depending on the insulators.

I always use and recommend an isolation transformer when working on these type of sets. The comment not about using an AC/DC radio (or the above mentioned TVs) in a wet area is correct. Our local radio club was set up at an outside festival years ago. It had just rained the day before, so the ground was wet. One our members got a shock from a 1930s Sears radio with a metal case. He could not let go until someone pulled the plug. Luckily he was not injured. In this case, as in many 1930s sets, there were no insulators!

In fact, I have several 1930s radios with exposed mounting screws, etc that are hot when the radio is plugged in. Things were pretty lax in the 1930s.

[Eric H]

I've never seen a polarized plug on a TV from the 1950's, not sure when they started that exactly, late 60's early 70's maybe?

[Electronic M]

Originally Posted by Jeffhs

Anyone who would use an AC-DC radio in a bathroom is taking a terrible risk. I did not realize fuses and circuit breakers will not open or trip, respectively, at just 30 milliamps; it would have saved many more lives if they had been designed to open the circuit at this current level. I can understand why fuses cannot blow fast enough to prevent electrocution; however, would it be possible to make a circuit breaker sensitive enough to trip at 30 milliamps or less? Of course, a sure-fire solution would be to get people to stop using AC-DC radios in bathrooms, but some people just don't get it that they are putting their lives at risk doing this. This kind of hazard is probably outdated today as far as AC-DC radios go (most people trashed their AC-DC sets years ago when transistor sets became popular or never owned an AC-DC one), but it is still a risk with appliances. As I mentioned in another post, a baby was killed decades ago when a toaster fell into the kitchen sink where the child was being bathed by its mother, and there are probably countless other accounts of such fatal accidents as well.

This is why today's line-powered radios, televisions, and appliances are now equipped, by federal law, with polarized AC cords, and why, as DavGoodlin mentioned, the National Electrical Code now requires GFCI (ground fault circuit interrupter) equipped outlets in damp locations such as kitchen sinks, bathrooms, basements, laundry areas and the like.

BTW, the "hot chassis" design did not disappear with the advent of all-solid-state radios and televisions. I have a late-model (1999-2000) RCA 19" color TV which has a hot chassis and, of course, a polarized line cord. One major hazard with this design is if, for any reason, the speaker leads are shorted, to each other or to ground, the television will be seriously and permanently damaged.

I don't know, however, if the same thing can happen with hot-chassis tube-powered radios or televisions if the speaker(s) connections is/are shorted. Tube-powered AC-DC radios may be more forgiving of this type of short, although I would think a solid-state AC operated radio would be destroyed in an instant if the speaker(s) was/were shorted to each other or to ground. The former (speaker leads shorting to each other) seems to me to be more likely to permanently and severely damage the radio, making it instant junk. I also think that if the speaker(s) were somehow shorted directly to ground, there would of course be no sound and the house fuse or circuit breaker might open or trip, respectively; there should not be any permanent damage done to the device in which the speakers are installed and used.

Yes there are almost certainly such a thing as 30mili-amp breakers and there are definitely fuses at that rating, but to suggest installing them in a home electrical panel shows a clear lack of understanding of electrical fundamentals. To illustrate: Watts = Amps X Volts and a mili-Amp = .001Amps so a 100 Watt incandescent lamp being ran at 120 Volts draws 833 mili-Amps, if you look at your vacuum cleaner it probably boasts a 12 Amp motor, and the filament in the average tube draws 300mili-Amps......Thus if you installed 30 mili-amp breakers in your home electrical panel and tried to run ANY of the above appliances (or just about ANY common home appliance) off that breaker it would trip the moment any of the above are turned on. Thus making 30mili-Amp breakers useless in most applications where they could save a life.

In general it takes very little energy to kill a person....we use daily in our bodies alone enough energy to kill ourselves several times over just to breathe ,move, etc. Taking the energy we use in things like appliances and cars on a daily basis in to account the average American probably controls enough energy on a daily basis to kill the population of a large country. However most things that use energy are designed to do their best to prevent all, but motivated or unlucky individuals from actually using them in a lethal in a lethal manner.

[Electronic M]

Originally Posted by Eric H

I've never seen a polarized plug on a TV from the 1950's, not sure when they started that exactly, late 60's early 70's maybe?

My 71' Zenith is non polarized, but my 77' is so I'd say mid 70's is when polarization became standard.

[David Roper]

I have a ~68 Portacolor with original polarized plug, the oldest example of their use I've seen on any appliance by a margin of nearly a decade.

[dieseljeep]

Originally Posted by David Roper

I have a ~68 Portacolor with original polarized plug, the oldest example of their use I've seen on any appliance by a margin of nearly a decade.

Starting with the 1961 model year, all the hot chassis Motorola sets had polarized plugs and interlocks. Many others did as well. I think it made it easier to get U/L approval.

[DavGoodlin]

I incorrectly stated in the previous post that most series 1950's sets had polarized interlocks/plugs. DUH-me on that. Neither of my 1956 metal-case 14" BW sets have them and neither does my 1958 Philco seventeener. My 1963 Westinghouse attache 19 BW TV did have a polarized plug. Being an electrical switchgear manufacturer, Westinghouse took safety a bit further than others. This was probably optional for a long time before UL required it. Must do some research on that.

I got zapped quite a bit by 120 in the old days and fortunately I recoil as opposed to clenching. A Sunbeam mixer shocked me and trip the GFCI simultaneously one time. I put a grounded cord on it after that.

GFCI receptacles are OSHA required at construction sites due in part to the fact some tradesmen use older, metal case power tools where the ground pins were routinely cut off. I see guys working around puddles on concrete before a roof is on.

GFCI is simply a current transformer surrounding both line and neutral conductors. It does not include the ground conductor, nor does it require one to operate. If ANY current is going out on the line and not returning on the neutral, the differential current (usually only 6.8 mA) is detected and trips the unit open. There have been improvements over the last 30 years so they don't false-trip so much, such as from a static arc, etc.