When I was a kid back in the 50's, I'd routinely get zapped off metal cased radios. I learned to isolate myself instinctively and to flip the polarity around with the plug. It wasn't just radios that had this issue. I noticed it too with certain appliances like toasters and refrigerators. Amazing times back then.

These are all great comments! I acknowledge that some folks are unable to accept the level of risk associated with AC/DC sets or having a handgun in the house, or owning a pool, or flying, or a dog, no matter the measures taken. And it's not personal. Most of us hams consider the novice or untrained and what might happen to that kid as the worst case. Insurance companies have to consider the general public and completely untrained against any benefit to the manufacturers or the public, and make a guess as to a level of safety that is acceptable. So even if there is some safety level associated with say - the Specific Absorption Rate of RF against your head with your mobile phone, and it is tested in a lab, some still may not be comfortable with it. That's Normal.

i built that Knight Star Roamer when i was 12....still have it,,, did have to recap it last year ,,

Thanks for the trip down memory lane. My dad gave me one in the mid 60's and I had it until the 80's. It got me on my way to getting my ham ticket. I loved that radio.

Some of these older receivers don't even have a fuse, let alone polarized power cables, wonder how many folks back in the day would actually gotten zapped! I just uploaded a video where i installed a fuse and a polarized cable on a Hallicrafters. Thanks for the info!

More common than the shortwave radios were the two wire, non-polarized "All American Five" AM radios, such as the clock-radios found in kitchens all around the country during the 60's. Somehow most of us survived.

Across your hand even without the network the 120v wouldn't kill you. You would get enough of a shock to violently jerk your hand away, and that could injure you. However, if you touched the "hot" ground with your hand, but your other hand was grounded, now you have a current path that goes through your trunk, which could shock your heart and cause cardiac arrest. The current required for that is just a few tens of MA. Wet your hands in brime and then measure your skin resistance. It could be less than 1000 ohms! Sweat will do that too! BTW, while Knight Kit designed the Star Romer with 6.3 volt tubes and a power transformer, Heathkit had several models that used the standard All American 5 tube set, BUT they had a 1:1 isolation transformer in the power supply.

I feel fortunate that I survived my experience of learning about AC/DC sets early on when I started restoring antique radios. I lovingly refer to my 1950 Silvertone Model 2 as the "little radio of death" since it has a metal case that had a 50% chance of being electrically hot even when it was turned off. While holding onto the PL-259 end of my amateur radio antenna (which was grounded), I leaned on top of that radio with my elbow by mistake. I put a polarized plug on it after my arm stopped tingling.

Excellent video with great explanations Mike. Safety first !

Had an old one as a kid and it used to give me a tickle all the time until I mentioned it to a local Ham G3RXH. He explained it was an All American 5 underneath and told me to get a 1:1 mains transformer from a bathroom shaver socket and put that in between the radio and the mains. He was a kind man, my Elmer. R.I.P. Howard.

I recapped my Hallicrafters S-120 and made a 2-part video here on KZfaq (Jan 2021). As I recall, it was a nightmare to work on. I had to rely on 2 parts radios. One was a Lafayette HE-40. Almost identical, except it also had an S-Meter. Even after the recap, I had to work on reducing the hum. I sold it at NEAR-Fest soon after. It went to a good home. It was nice to see you there at NEAR-Fest. I think I saw this radio on your table, and we talked about it. 73 Paul AA1SU

I'd like to see how to properly rewire an old piece of gear for a modern 3 prong plug. Many sites will just say "Of course I rewired the radio to a modern plug.." But do not show what is done safely....

Early on in my radio days I was told to keep one hand in my pocket if i am working on a live circuit. That probably saved my life more than once when I was a teenager

I used to have a Hallicrafters S-86 half a life time (15 years) ago. There are a few videos of it way down on my KZfaq channel. The first time i was gonna test it, i almost touched the case. I knew it was an AC/DC set, but all Philips ac/dc sets are completely safe and well engineered so i thought 'Eh, it'll be fine'. But a little voice nagged and made me measure for voltage, and there was the full 230v mains on the case. After recapping the thing, the short was still there. I never got around to actually finding that short. For a couple of weeks i used it like that, just measuring the voltage each time, but shortly aftermaking the video on my channel i hardwired a 230v-110v isolation transformer into mains cord, and ripped out the 220v-110v autotransformer. I eventually sold it to a friend who knows his way around mains safety, explicitely notifying him of the issue. So yeah, those Hallicrafters things are pretty dangerous. Incomparable to the Philips AC/DC sets i'm used to.

Hey! Former Project Manager at U.L. in the early 2000s, specifically in Wire & Cable but I also mingled in all other fields too. Companies don't submit reports to be certified. They send in a sample of their product and then it is thoroughly tested by the engineers. For instance, in W&C, there would be burn tests, crush tests and the like. In plain English, if stuff didn't burn more than it was supposed to, or break down with less force than was reasonable, then it got the seal of approval. There is always a battery of tests suitable for the field the product falls into. Basically, U.L. makes the report and not the submitting company. Rock on.

Great information. This goes for any AA5 receiver on knowing it's limitations and how to improve the situation to make these radios safe as posible. Thanks for making this video Mike. Steve

Back in highdchool on the late 60s everything i built was tube & powered directly off the 117V AC line...receivers, AM transmitters, guitar amps for my brother's rock band

Reminds me of playing through an old guitar amplifier. "Hey, it tickles!" All fun and games until you touch your lips to a microphone and wind up laying on the floor seeing stars, or worse maybe seeing your maker.

In the 1980s I used my Hallicrafters sw 500 to listen to cordless phones around 1.7mhz, I used to reverse the plug in the wall socket and the radio would oscillate, and It would jamm the cordless phones. for a 1/2 mile radius.😄

My uncle had the Halicrafters S120. He used to listen to the old country (Radio Netherlands). I would love to pick one of these up.

Though everything you said is true, I would still treat that type of technology like a hand weapon. It is always loaded even when it isn't. That safety capacitor could experience a freak isolation breakdown. A small piece of detritus could dislodge inside the chassis and short something. An insect could carbonize between to points of high potential. Highly unlikely? Certainly. But, unless it is transformer isolated, I would consider it risky at best. In my own defense, I love these old radios. I am simply preaching caution. You only have to be wrong once. Then it's too late.

My S-120 never tried to kill me, but I was shocked (literally and physically) as a 14 year old when my S-38 tried to bite me! My S-19R with onboard isolating transformer has always been a peaceable Sky Buddy of radio😃- DE K1TB

I've only come in contact with radios with a transformer. Sometimes there are either capacitors or resistors or both on the AC line to ground. They are simply not needed, and I remove them. I then replace the 2-prong line cord with a 3-prong line cord and ground the chassis. No tickle, no surprises, no issues.

Very well done. I have several radios I plan to restore. Good reminder to check little things.

I typically use a polarized 3 wire plug. Connecting the green safety ground to exposed metal parts when possible. If the chassis is “hot” , I connect the neutral (white, current carrying conductor) to the chassis. This can put the line side 120 v on the antennae as shown in-the video. The best way is to always use an isolation transformer. A safety ground is only supposed to be active in case of a ground fault, normally never carry current. The white neutral always carries return current. Neutral and safety ground return to the same point, but the safety ground is typically less resistance and shorter path to ground.

Valve (tube) tv sets in the UK were non-isolated and remember that's at 240 volts, fine to fix in the workshop with an isolated bench supply, but you had to be very careful in customers homes. I remember at one house, every time I unplugged the set, the customer who I suspect was suffering from early dementia, plugged it back in. I only noticed because the filaments started to glow. I also remember on numerous occasions, having to quickly grab the arm of an enquiring customer as it delved into the back of their live set. Luckily I didn't do that job for long, I don't think that my nerves would have held out. Steve

I still have my s-120 I purchased used from a pawn shop back in the 1979’s. Paid way too much for it. Generally a nice SWL receiver and a touchy ham receiver.

Excellent illustration of early line isolation. I might mention the show and tell part of would you feel this; the completed circuit path was between two fingers on the same hand; Old timers voltage tester. May be a little more noticeable if it passed through your body with your heart in the path. Also pre GFCI days threshold of 30 ma. I can understand not wanting to complicate the issue. Thanks for a easy to understand video.

Oh, so now I get some of the tingles I've felt before. But then the last time I felt it on my battery charger (transformer type). I'm learning. 73

I was given a Hallicrafters as a child, too young to appreciate what it was. I don't even know what happened to it. All older electronics were not built to the same standard as new ones. Safety capacitors Y or X types had not been invented and metal chassis were often powered by one side of the line. Used to listen to Hawaii radio from Los Angeles. Never trust old electronics the way you might trust quality new equipment, which includes things as minor as using it with bare feet on a tile floor. C30 should be a Y-rated capacitor. I would love to have that radio now.

Yea I had this problem with my first radio, the SX-99, back in 1957.

I liked it. I have a eico signal generator that I replaced the 2 line to chassis cap with safety caps and left them in. It'll tickle you a bit, but it's not going to hurt anyone, plus I didn't want a second ground path when using it. Some people have no risk tolerance.

Personally, I would make it a 3-wire cord and not rely on the polarized plug, which is easily reversed using a worn-out extension-cord! I really think that it was a huge-mistake to make any ham-equipment line-operated since there is much more chances of both the 'novice' getting inside it and various hook-ups that might be made while experimenting with antennas and such. Finally, the immediate danger of hooking test-equipment to the receiver and depending on that person either having an isolation xfmr (ha-ha back then!) or automatically knowing to check the potential difference beforehand! 73... Edit: There is another reason I feel this is bad: The first time someone without knowledge of this phenomena gets a 'tingle', the radio is probably going in the trash can or will at-best become a shelf queen!

I have 2 S-120's. 1 for parts. The other for posterity on my shelf. Not that great a receiver, but hey, I have one! And the 50C5 runs smok'n hot!! --- Wanted to send you an email about some MOD's, but you don't allow them, so that's that.

I once owned a Hallicrafters S-120. It has what is known as a "hot" chassis. Plug it in the wrong way and you got zapped. My Mom and Dad owned a Muntz tv way back in the day also. That television also had a hot chassis. I remember very well getting shocked by that thing.

there was some UK Eddystone models that used 'live' circuitry, the inner chassis was common circuit negstive and connected to one pole of the mains but the outer metal cabinet was isolated from it with plastic spacers and standoffs, potentiometers and controls had their own plastic grommets, AND it was also earthed to mains earth, it had a 3 core mains lead, BUT the plastic insulation and spacing was good enough if you had to use it with a 2 core supply for some reason,

Wow - How did you know? Recently picked up an S-120 and before even touching the thing I downloaded the schematic and identified the exact points that you showed in this video. Thanks for the heads up on the recap kit.

For bench testing AC/DC stuff or any exposed 120 work I have a GFCI outlet in a box with a short power cord, not something you should be tripping often (tests aside) but it will protect you from any real current flowing from live to anywhere except neutral if you screw up.

Modern stuff is built the same way, DVD players, phone chargers, etc. Every two wire swithing power supply, any metal case two wire electronic device. Some stuff like the phone chargers are even unpolarized, you don't get bit because you usually aren't earthed all that well. The only difference is they use safety caps and fairly high voltage resistors.

I still have mine. I got a nasty shock from it the last time i used it. I guess I need to put that kit in it. I broke 4 vertebrae in my back, so I have plenty of time on my hands to fix it.

S120 had a hot chassis which cost me money years ago when I had to add an audio amp that was hot chassis also. The receiver was not legally UL approved to even be earth grounded for the antenna. Ended up trading it to a fellow CB/Shortwave listener that used headphones. Lol

Chassis is hot put it on the isolation transformer

Back when I was a young teen just getting into working on radios, I quickly learned to reverse the plug in order to not feel the tingling or a shock, when touching the chassis or any exposed metal parts. Never made any sense to why direct ac-dc line powered radios were made, by the 1960's how many utilities still served any customers with 105-125 volts DC? These kind are bare minimum sets, just enough parts to have mediocre performance in most designs.

"Widow-maker receiver" 😂

Interesting how our two countries differed in their thinking on electrical safety. The UK had a 3 pin plug system which prevented reverse polarity and had an earth wire from an early time...BUT they were running at 240V AC and now have dropped it down to 220-230V AC to conform to European standards. 230V shocks are not funny!

I remember when I was a kid probably 4 or 5 or so I can't exactly remember when but I remember plugging in a clock and my finger got caught between the plastic part of the plug and it was touching the metal prong and oh boy I sure as hell felt that shock it felt like my body was buzzing and it didn't feel like a tickle to me but then again I was a little kid so I felt it more and ever since then I've been super careful when I work on electrical stuff.

I got given a Texas star for cb had some mods and it would burn my truck , crazy as it sounds, it’s old 86 Nissan 4x4 but it burnt my reg cd radio above it out the heater connection behind, I key up in beginning it would shut lights off at night but capacitors where grounded to the outside of box when took it apart, I had it redone nothing burnt so far , lights still dim but it talks to Maine from TN

Just plug in isolation transformer if you are servicing. Real issue is that mains noise feeds back into the antenna as there is no isolation transformer in these which isolate the noise also

I am not surprised that the Hallicrafters is better than the Knight (all else being equal). Hallicrafters seems to be especially good for squeezing performance out of budget builds. I am not entirely sure how they pulled it off sometimes, better inductors maybe? I did a Hallicrafters "Continental" for a friend (just a plastic AA5 set) and well, who hasn't done a few mass produced AA5s from the 1950s at some point or another? The Hallicrafters would beat the pants out of all of them in performance AM broadcast dx'ing, yet utilized the same tube lineup to do so. Imagine what they could have done if they'd had more "cost is no object" models and catered to high end ham or military markets.

I have been bitten by that radio many times but not since I was 15 years old - No transformer at all as I recall and series filaments. Ultimate cost cutting back then. This radio did not have an RF amplifier either.

Hallicrafter bit my lip often! Lit me up like a electric fence!

IIRC, the UL rating isnt so much about the electrical safety of the product, as it certifies the product doesnt present a fire hazard,. Adding a polarized Line cord is a big improvement in safety. I believe CSA(Canadian safety organization) required polarized cord long before they became common in the US.

What are we going to do tonight, Brain? What we always do, Pinky, we're gonna take over the world! muahhahaha.

Why the big difference in audio, starting at around 2:33 ? I kinda like the first style, for what its worth.

Can you make the S-120 shower safe? I feel asleep halfway through. Why do you recap? Do you replace your teeth just because they are old?

As a 22 year old, I built a Philmore ac/dc 3 tube Regen rcvr It was open and dangerous!!!! I got shocked several of times with it's open metal chassis! Hi one stupid!

Aviation moved to VHF FM decades ago.

I had the S120 and like most of the radios of the day it had the 0.1 Mfd death cap

S120 is good i have 2 of them

Measuring voltage on the chassis with a 10Meg ohm meter doesn’t really tell anything useful. You need to shunt the meter with a reasonable resistance to really make any read of leakage

Why not find a spot to mount a 1:1 isolation transformer and be safe no matter how the receiver is plugged in? That is how I have built my bench power supply (a variac, isolation transformer, incandescent bulb and outlet.).

My uncle had an S-120 in the Army in Germany. Deaf on 10M.

I am kind of intrigued by the comments and the perspective of the video. The UL standard may have changed since 1960? Doesn't "dual-insulation" require a thick plastic case? Is the 3-pin plug really acceptable as a polarizing plug? Can a "dual-insulation" equipment be fitted with extra connectors such as "earphones" or "antenna"? If I were a young radio enthusiast, one thing I would like to do is to connect the speaker output to my computer audio input? How difficult would that be to retrofit the instrument with a properly insulated power supply or transformer? The real thing! Why not? Walworth adapters are intrinsically safe. It does not come to mind easily to young people who never knew anything else that mains outlets are dangerous. Even less with high DC voltage. Voila. My two cent. Tube electronics really scares me...

I've never met a person who had been killed by electric shock.

If you are building a kit you should know the dangers of tube receivers transformer or no transformer. I built a greymark 2 band radio and there was no isolation transformer. Common sense would tell you to take a neon test probe and make sure the chassis is not hot. My first TV had a polarized plug and my Uncle shaved off the neutral side of the plug so the TV could be plugged in an extension cord. I always looked where the neutral is before pluging it in. Some say about headphones but the output already has a transformer so whats the problem just dont mount the jack on the metal part of the radio mount it on the plastic case. These are safety measures you can take to protect against shock. I have one of those radios and i would first check polarity of the line cord. Thats what a multi meter is for. If you are not smart with electricity dont modify a radio. 73

Nice content! Wondering if any custom PCBs may help for any upcoming radio projects? If so, would love to supply and reach any collab together if there's a chance! 🤗(PCBWay zoey)

Undertakers Laboratories

The S120 will zap the hell out of you if you plug it in wrong yikes

Yikes.