Monarch "Hi-Fi Master" Plastic AA5 Tube Midget AM Radio

[Robb]

Originally Posted by truetone36

Yep, it's true. Hot chassis sets can zap you if you touch any of the metal surfaces while there is any power going to the set.

Why would the Japanese build them like this ? Did they want to kill Americans after WW2 ?

[Electronic M]

Originally Posted by Robb

Why would the Japanese build them like this ? Did they want to kill Americans after WW2 ?

We built them the same way in America before and after WWII....In fact the early ones we made in the 30's before designing the tube filaments to properly drop the entire line voltage were even more dangerous as the third wire in the cloth power cord was the dropping resistor for the filaments, and it had a reputation for getting hot enough to set the insulation on fire...They called those sets curtain burners.

I own and have gotten shocked by some American hot chassis sets. As long as you are not well grounded it don't really hurt, it just tingles a bit.
There were UL approved hot chassis sets that were potentially lethal like their non-approved brethren...They would just not kill you as hard/easily.

[jr_tech]

Cute radio! It appears to be slightly smaller than the little 5 tube Emerson radios shown on this old "Small & Cute" thread:
http://www.videokarma.org/showthread.php?t=251125
Love the color... great find!

jr

Edit add: Old thread about somewhat dangerous METAL cased sets:
http://www.videokarma.org/showthread.php?t=251051

[dieseljeep]

Originally Posted by Robb

Why would the Japanese build them like this ? Did they want to kill Americans after WW2 ?

If you look at your radio, you'll find, an interlocked back panel, set screw knobs and the metal strip holding the chassis and the back panel, isolated from the hot chassis. It wasn't any more dangerous than any other radio made at the time.

[Robb]

Originally Posted by dieseljeep

If you look at your radio, you'll find, an interlocked back panel, set screw knobs and the metal strip holding the chassis and the back panel, isolated from the hot chassis. It wasn't any more dangerous than any other radio made at the time.

So if I touch these back metal parts of the radio, while it is on, I will die ?

[Jeffhs]

Years ago, I had a metal-cased Arvin model 540T AM radio. The case was green, the knobs plastic, and the radio used a short wire as an antenna, with a terminal on the back cover for an external one if the owner was in a weak-signal area and wanted to use an outdoor wire. Mine worked well for what it was, but as others have noted for radios of this type, it was a hot-chassis set; as such it could give the user a good shock if he/she touched the chassis or the external antenna terminal and ground at the same time. The chassis was supposed to be insulated from the cabinet by rubber grommets, but these often dried out over time, became hard and even conductive, effectively connecting the radio's hot chassis to the metal cabinet and, again, creating a serious shock hazard. I once read, in an old appliance repair magazine of the '50s-'60s, of one such radio that was installed on a shelf in a bathroom. The user was in the tub and tried to change the station or adjust the volume while still in the water; the radio somehow fell into the tub, and the lights went out when the house fuses blew. This could have had a very sad ending if the fuse hadn't blown, of course: the person in the tub could have been killed instantly by electric shock as soon as the radio hit the water.

One of the best things to happen to table radios, IMO, was the introduction of all-solid-state sets in plastic cabinets. This all but eliminated the shock hazard, unless the user ignored the warning on the back cover against removing said cover while the radio was plugged in and turned on. Some of these solid-state AC radios had interlock plugs on the back covers, as were commonly used on televisions and tube-type radios of the '50s-'60s, in an attempt to prevent such disasters.

Of course, the best way to prevent such accidents (and their horrible consequences) is not to use any kind of electric or electronic device (with the exception of electric shavers or hair dryers) in a bathroom or kitchen, although today's National Electrical Code requires that ground-fault circuit interrupters (GFCIs) be installed in bathrooms, kitchens, laundry areas, etc. of all new homes, or when upgrading the wiring in an older structure. Still, however, I would never put blind trust in a GFCI that it would work in every circumstance, or deliberately trip one just to see if it works, although most GFCIs have a test button which will do just that. I read an article in Popular Science or some other hobby magazine some years ago which stated, point blank, that GFCIs, fuses, circuit breakers, etc. are like fireproof buildings: good to know but unwise to test.

[dieseljeep]

Originally Posted by Robb

So if I touch these back metal parts of the radio, while it is on, I will die ?

Those are the items I mentioned, as isolated from the line.
IIRC, the rivets near the top, are for a metal shield, to keep the cabinet from being damaged from the heat of the output and rectifier tubes.

[dieseljeep]

All the metal cased Arvin radios I've seen and worked on, have a floating B- line, with a capacitor from the B- to the chassis.
The cap will pass a small amount of AC voltage to the metal cabinet. It will probably trip a GFCI receptacle, as they are designed to trip at about 20ma leakage. That is dependent on the position of the line plug. Also, if the switch is on or off.
All the receptacles in my workshop are GFCI protected.

[bob91343]

As I have previously mentioned, I am still unsuccessfully looking for one case of a person being electrocuted by 120 V power line. Everyone is paranoid (including UL) but all it seems to do is give people a shock. I get more damage from grabbing the wrong end of a soldering iron. I have been doing that for about 70 years and am still alive. Not to speak of the even higher voltages I have felt.

[jr_tech]

120 V can kill!
http://ecmweb.com/content/case-120v-...cution-mystery
jr

[Sandy G]

I wouldn't mind if that l'il cutie could kill-I still wouldn't mind havin' it ! And if it did, So What ? At least I Went out doin' somethin' I like-Playin' w/a Radio... Better that, than rottin' away in a bed somewhere, pipes & tubing runnin' out of yr Guttiwuts 10 places...

[bob91343]

After reading that link I am still unconvinced. It's not clear that a life was lost due to electrocution; there isn't enough information to be sure.

If indeed it was electrocution, apparently it wasn't instantaneous and the guy descended the ladder in a state of shock. His vulnerability to heart trouble wasn't established.

So I agree that it can happen that someone can be electrocuted by 120V. But as stated in the article, it is very rare. If you are elderly, or have a history of heart problems, it's wise to escalate your precautions.

On the other hand, I am 81 years old and recently have received several 120V shocks with no ill effects. Maybe I'm an exception or maybe the character of the shocks was such that current didn't reach my vulnerable areas.

The bottom line is that I still feel that there is excessive paranoia here. It's much more likely you will be killed in an auto accident or by a temporarily insane mate or acquaintance, yet very few people seem concerned over the possibility, certainly as compared to 120 V shock.

[maxhifi]

Just don't touch metal
On the back of an ac/dc radio when it's plugged in... Then no
Problem, the knobs are Always plastic

[Robb]

Originally Posted by maxhifi

Just don't touch metal
On the back of an ac/dc radio when it's plugged in... Then no
Problem, the knobs are Always plastic

Ya but what I dont understand is if they knew this could possibly be a safety issue, why in the world did it pass inspection ?
What would it not have rubber to cover the metal parts on the back or something like that ?

[Sandy G]

Originally Posted by Robb

Ya but what I dont understand is if they knew this could possibly be a safety issue, why in the world did it pass inspection ?
What would it not have rubber to cover the metal parts on the back or something like that ?

People were ASSUMED to have a SMIDGEON of common sense back then, unlike today..