Greetings. As the author of the "infamous" Death Cap video referenced in your presentation, I feel obligated to offer some insights. 1.) The video was created 6 years ago and is somewhat simplistic in its approach, as was my understanding at the time, but it was an honest attempt to bypass the hysteria and factually evaluate "Death Capacitors" in circuit. 2.) I use the rather imprecise term "hum" to cover all extraneous noise which could enter the circuit via the primary wiring. 3.) To be more thorough, I should have reversed the AC plug and repeated the voltage and current measurements, but at no time would plug reversal ever result in "full AC voltage to the chassis" of any of the amplifiers. 4.) That said, my observations were based on the data at hand, rather than hearsay, and were offered as opinion.....to affect the handling of the vintage amps in my own collection, which I preferred to keep in original condition if possible. In the one case where the "Death Cap" demonstrated current flow to the chassis, it was removed. I personally see no issues with the conclusions and would caution people to recognize that opinion is not fact, regardless of whose opinion it is, and when opinion does not agree with your preconceived notions, it is not necessarily wrong. I enjoyed your video and found it to be quite thorough and well presented. You offer logical choices for the prevention of shock hazards and ground loops, which prove helpful to many viewers. Thanks for posting it.
Hello Uncle Doug. Didn't mean to stir up anything with that portion of my video, I just kept running across sites that quoted it as being flawed when I was making this video. As I mentioned, sadly I hadn't watched your video so in fairness, I probably shouldn't have posted that. I have the utmost respect for you and what you do.
I did find it a bit strange that you would take the time to cite my video as being flawed, especially since you had never watched it, but no doubt all videos that express opinions.....and all do.....are flawed to those whose opinion differs. Regardless, I found the portion of your video that was dedicated to the topic to be factual and very well done. Thank you for your effort in that regard.
@@UncleDoug I find it refreshing that you are owning up to any mistakes that may have been made. I also haven't watched your video on the topic, but I might have a look since I am studying up on the subject at the moment. May I ask, if there was indeed "not quite right" I guess you could say, information in that video, has it been amended to reflect the new information? Not to offend, just that if it was me, I would have made a change or two rather than leave it up. But as I said, I haven't watched it yet, you may have done this already. And yes, sadly when it comes to electronics, there can be different interpretations of the same basic knowledge unfortunately. I'm sure the majority of your info is more than solid. I will take a look in the morning and most likely subscribe to you as well! So great to have some actual experienced minds to watch and learn from!
@@ballsrgrossnugly The video was not amended......there is no means to do so, MM.......and I still feel that it served a valid purpose. I never said that it was "not quite right", but could have been more thorough......let's face it, so could virtually all such videos. It is still my contention that an intact "death capacitor" in an amp with a properly installed 3-wire chassis-grounding power cable is a non-issue.
@@UncleDoug Still awake lol maybe I should just watch the damn video instead of assuming huh? Yeah the way you explain it, it's at least not a safety issue. Maybe a buzz issue but that's not the point of a safety warning. Fair enough. I'll watch that video rather than comment any more and securely place my toes down my own throat!
Finally, a video that covers the topic well and discusses all the decent options. Now I can point folks (customers) here to educate themselves. Thanks Mark. Well done.
I have a fender twin reverb guitar amplifier. I threw away the two prong cable and installed a three prong one. I grounded the cable at the base of the power supply transformer and cut out the dearh capacitor. No problems since then. Better safe than sorry! Nice video!
At first I thought this was about old paper type capacitors that fail, start passing current and destroying electronic parts but now I see its about the equipment trying to kill people. Years ago we had a lot of old tube amps for my brothers band and you had to pay attention how things were plugged in. One time I watched my brother step up to microphone and get big blue flash right in his lip
My first live performance in 1966, I had a tiny amp for a mic and another tiny amp for my guitar. As soon as my lips touched the mic, I was almost knocked out and my face was uncomfortably numb for about a half-hour. It took me another 30 years before I was able to shake my mic shyness.
Thank you so much for this. I have a basic background in theory from my electrical apprenticeship and the way this is all presented makes perfect sense to me. This will be the video I send to other people to explain the concept. I filled in a ton of gaps with this thanks.
"Hot" chassis in tube radios was quite common up into the 1950's. My father taught me how to properly orient the plug using an NE-51 neon bulb with a resistor.
The capacitor layouts may be common to audio amplifiers but transceivers (two way radios) almost always have at a bare minimum a cap from hot to chassis ground and one from neutral to chassis ground. For this application some vintage tube radios used a (popular at the time) very large ceramic disc capacitor that had 3 terminals. It was basically two capacitors in one ceramic capacitor package. Some radios used a 3 capacitor layout. The two mentioned above and another across the hot and neutral. In solid state units that did not have a 3 prong earth ground type cord it is also common to have a high resistance resistor tied from the common line to the chassis for a earth reference. In ANY radio and I mean ANY vintage radio be it solid state or vacuum tube type always replace all these capacitors. The ceramic types fail just like old paper caps did. Only difference is they dont slowly short out over time. They go from working perfectly to dead short. They are attached to the mains any time the cord is plugged in and get the snot beat out of them by power line surges. I have seen several dozens of them that have exploded over the years. One that even caught the radio on fire when it shorted out in a Tram D201 CB radio. When it shorted out near the power transformer it caught the transformer insulation paper on fire. You can find modern x1 y2 rated capacitors from almost all the large electronic supply companies like DigiKey, Allied, Houser, Newark, etc. Most of the time the problem is people have a hard time finding them on their websites because they don't know what ratings to search for. A good source if you work on tube gear is www.justradios.com . David and Babylyn have a simple to navigate website and sell these capacitors. All the capacitors they sell are on one large page. They specialize in repair parts for tube gear.
I never understood the big deal about the death cap - lots of things would have to go wrong in order for it to kill anyone. First of all if it shorted, it would blow a fuse. If it didn’t do that- it would trip the breaker switch at the panel. If for some reason it was a partial short - it would starve the primary side of the P.T. Of voltage, thus your amp wouldn’t work. Even if it did, the plug in wall would have to be reversed. And if you have no center taps to chassis ground on the secondary side - then it’s effectively an isolation transformer, and nothing will harm you.
Not only the plug can go either way you need to know the socket is wired correctly, just don't assume anything with mains power and keep one hand in you pocket.
The keep one hand in your pocket it some really good advice. I have hurt myself measuring voltage by laying my other hand on a heatsink. I quickly found out there was voltage going through it
Seems the best bet is to buy one of those testers and plug it into the socket before trying the amp! 2 extra minutes could be that life saver you need!
@@tmastersatYes that is true but some plugs are not polarized hence the risk. Most European plugs are not polarized either and they carry 230 v . The UK plug and socket are polarized and each plug is fused as well as circuit breakers but I have seen them wired incorrectly. The new UK system is to have completely sealed plugs so no one can do anything but change a fuse. Just to say if there is a way to screw it up someone will.
Great job ! I understood all of that. I especially appreciate the information regarding the different recommended approaches for handling a vintage guitar amp versus a vintage piece of audio gear, since I own both. Than you very much.
Hmmmm - TV sets have cabinets that protect fallers. The cathode ray tube's 25K anode voltage connections are insulated. The 25K in one arm won't kill you (I've proved that by accident several times.) 25K in one arm won't restart your heart
Thank you, Mark. This is no joke at all. I got a huge zap from plugging my guitar into an old vintage Marshall amplifier that was in for repair at my buddy’s shop. The second l touched the strings, I thought my friend had run full speed across the shop and jammed his elbow between my shoulder blades or slammed me in the back with a baseball bat! It felt like a truck had hit me. He of course didn’t do that, but a big zap is a very scary thing that you don’t forget. This happened to me around 25 yrs ago. I am of course extra careful when I am poking around inside any gear since then, whatever it may. Use a chopstick to check around and keep one hand in your pocket.
same here, a Fender Quad reverb. I was standing up playing through the amp and for some reason I reached over to switch channels on a small TV and that's when a giant hand picked me up and threw me Gainst a wall, scared the living crud outvof me and taught me to double check all Earth/ground wires on ",Everything and to use a "Discreet" socket just to power my Guitar amp and nothing else, nastyvnasty shock!
@@stephendickson2007 I've been killing myself to live all my life. I'm dying to see how it all ends.
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No I know why (possibly) vintage Roland power mixer was sometimes electrocuting everyone with constant current flow. Literally one could feel current flow when holding grounds from two devices 😁
Now-days :-) Always use a RCD (Residual Current Device) circuit breaker, and power all your equipment through it. These are inexpensive devices, and can be obtained from most good DIY stores. These will detect any potentially dangerous current flowing to earth, and will immediately cut off the power quickly enough to prevent injury.
great video! new to tube amps and wanting to learn from the right spot. is this part of a series I can start watching? any good book recommendations for someone with ZERO electronics background to work on/repair/maintain tube amps?
What's this about plugging in things the wrong way in the USA? In Germany, you can plug in devices any way you like and it doesn't make a difference. I'm sure it's been like that for more than 50 years. What's the difference in the US?
My parents kept an old 'All American 5' style AM radio in the kitchen next to the sink. As an inquisitive 5 yr old, I one day pulled a knob off, exposing the metal shaft. Touching the rim of the sink as I leaned over to touch the shaft I got one heck of a shock. I looked at my finger to see if I was OK and was horrified to find my finger tip was 'disfigured' with a bunch of circular marks. This was how I discovered fingerprints.
Never could understand how North American standards allowed electrical plugs and sockets to be made in this way, they should be made irreversible to keep neutral and live in the same orientation.
I always knew about DC electricity and how it worked (enough to make repairs, and little projects and stuff) but had NO idea about AC Line and Neutral, mainly due to these plugs. I thought "polarity" didn't matter whatsoever with AC until I learned more about AC and the system as a whole and said to myself "Wait, what if another device is on the other side of that sine wave?" I thought I was wrong and looked that up, only to see I was right and those cords are old and dangerous.
He is talking about old fashioned plugs. Anything made after about 1975 has the blades different sizes so that you can't plug it in wrong unless you file the wide one down.
The current standard for NEMA-15 (North America - including Mexico & Canada, 110-120v @ 60Hz) has polarized plugs and connectors (one pin slightly wider than the other), as well as those with a third pin for ground. But yeah a lot of old stuff doesn't have it (which really isn't good), as well as plugs for things where polarization isn't supposed to matter. en.wikipedia.org/wiki/NEMA_connector Japan also has a very similar (practically compatible) standard. Not sure what their differences are though.
Thank you Mark. You are the only one, among many, that has dealt with this issue in a professional and code compliant sense (although some jurisdictions require a earth-ground metal chassis regardless of what other measures are in place). First priority is safety. Hums / ground loops are secondary to be dealt with separately. I used to build custom control systems which required a 'special' inspection /approval process by the local electrical authority. Not only did the Hammond metal cabinet require an earth ground but the door had to be electrically bonded to it even though it too was metal with a metal "piano" hinge and it had to be tied with ring terminals. No spade connectors allowed. The neutral is NEVER switched alone including fusing. I Thanks again for this.
Brilliant explanation!! I never thought of its use as a LPF. Capacitive reactance will act as a pseudo-resistor at 60HZ, limiting the current. Still get a nasty jolt, though, under the right conditions. Thanks for posting this video!!!
Excellent video as well as interesting. Great information foremost for safety reasons. Two of my guitar amps are more modern (a 1980 Mesa Boogie Mark IV and a circa 2011 Red Plate Hand Wired amp). However, I do an old Premier Guitar amp from either the early 1960s or earlier, that I thought of fixing and putting back into service one day. It would be safe to assume that amp has a death cap based on what you alluded in this video. (It the Premier model that has a triangular shaped head and triangular shaped speaker cabinet) and they fold and clamp together for transport. Thanks for doing a very detailed video on safety...BTW: I remember getting tons of shocks as a kid playing guitar when your lips touched the microphone. Who knew! Phil NYC Area
I agree with others comments - great vid that explains the issues clearly and offers a great example of Y cap use. Plus, gotta love adding a fuse:). Thank you!
Very interesting video, but you forgot to approach norms about security. These can differ from countries to countries, and accept different solutions. Anyway, for a direct replacement or for a switch filter, X2 caps are mandatory! X2 MKT or X2 MKP are supposed to be safe fail, or double insulation. Always choose a higher AC grade that what you need (250V for 110V supply, 330 or 400V for 230/240V supplies, the cost difference is not a problem, a few cent for much higher reliability!) Of course, it's always impossible to tell if these direct replacement will be the best solution, you have to consider many factors. In many cases, this is the worst! For instance in European countries, the problem is most norms imply high security electrical measures, with differential circuit breakers even for mobile sound. If the total amount of current flowing to ground surpass 30mA, in most cases, the circuit will be open in less than 25 ms, enough for a shock that won't kill you, and what seem instantaneous when you plug an equipment that is failing or so. Here a bad cap value can get you in trouble, because you have to choose from too much leaking current to not enough filtering... You have to test different strategies, implying snubber Y filters, Pi filters, a combination of two... An array of coils and caps that can be invasive and anyway unaesthetic. Enter the direct grounding with 3 wires solution you also propose. You mentioned the RF troubles you can get using that, and of course , if you encounter ground loops, you have also to consider chassis uncoupling, and the use of a small RC filter between Earth and chassis ground can be sufficient, as appropriate means of HF shielding, and a new approach towards partial or total return ground windings. Enter different schools, uni rail or star form, many using the main filter minus pole as the reference GND. A special mention there for beginners, in bipolar technologies or even tubes, this is not B- ! For best solution, this may imply you have isolated input plugs, jack, RCA or else, isolated pots, shielded separated lines ... Some would say a total reconstruction rather than a restoration with minimum intervention. It's a question of many factors, depending on how long you want to use it, how often... and last but not least of your budget! Nowadays modern equipment have regulatory limited RF emissive levels, and that part may be the most important budget in norms conformity assessments. So modern microwaves, welders, UPS, PC or whatever switching power supply are supposed to leave mains HF free. You are also supposed to have a high quality low impedance Earth. Alas, new carrier current technology like remote net plugs, electricity and gas meter, smart grid energy technologies, have recently polluted our environment with new HF waves. Some are efficiently filtered by mains transformer, some don't. A good exemple is a high end 1990's MOSFET amplifier with a large frequency bandwidth response which can be at stake, because interference noise can destroy it, even if you don't ear it! In most cases, in modern (1950 +) equipment, assuming you have a multi voltage mains transformer 240 or 230V in EU, a three wire cord is a simple and efficient solution to begin with. With silicon electronics, I usually try some modern filtering modules (Schaffner or else), that have to be choosen depending of consumed current. I know that solution is invasive and not too old style conservative, but it generally works fine and respond to most stringent security norms. Smaller ones (≤ 10A) generally come in a IEC plug form that can be fitted in a chassis, fine in replacement of a secondary plug... Some come with a switch or fuse... For tube chassis, other questions come: the presence of HF stages, tube microphony and shielding measures can also provide treacherous traps when it comes to try earthing methods. And If you need some insulating or downstepping transformer (230 to 110V), you will get systematic troubles. Ie: you buy an old 110V only radio chassis, the transformer totally isolate your chassis from mains, but you loose that advantage of you ground it! Some chokes can also become ineffective or even noisy, most are difficult to replace. Anyway, in many old apparatus, ground loops can appear, from input stages to antennas, from a single jack to a chassis mounted capacitor. You have no choice but try and find compromises, between modern fool proof security, maximum quality, and budget!
No idea how it works in the US. But in Europe, depending on the grid, we don't have a neutral out of the socket. It can be neutral 230v or 2 times 115v when it is an old 3fase 230v grid.
Hello thank you for your video. I have a bad capacitor on my old sewing machine on the motor with rating 0.1nF + 2x 2500pF. It is hard to find new with same rating. Any help on how to replace it? Thank you
As we don't have polarised plugs in most parts of Europe, this came to mind: couldn't you instead of filtering RF interference back to the neutral conductor instead filter it off to the protective earth conductor? That way you're not directly connecting the signal ground to earth, but in case the capacitor fails, you'll end up with a bit of extra hum either way regardless how the capacitor fails? And polarisation doesn't then matter at all?
Years ago my wife had found an old toaster that still worked, but I noticed that it had an old two pronged plug. I knew which way to plug it in, being an electrician, but I replaced the cord with a two pronged polarized plug so it is safe. Now...back in the day it could have electrocuted or given someone a bad shock if it was plugged in wrong AND the person was touching the toaster and say..a metal faucet. They then would have become a path to ground. I hope this scenario helps in understanding the importance of proper grounding.
Very good video lesson. Learned a long time ago that the caps didn't fail in the user's favor. Especially the radios with direct line-to-tube rectifier sets. All of my Heathkit equipment so far has had the two fat HV disc capacitors on both legs of the line cord to chassis. Wired as if they were safety caps. They are not! I always replace them with two X1Y2 safety caps and mark the neutral lead on the original plug when it is in good shape to keep using it. Otherwise the cord gets replaced with a two prong polarized version. Hard to find in gray though. Thank you for these informative videos. Subscribed.
Going by your schematic, the "death" capacitor is not the problem. Tying the neutral line to chassis ground is the problem, even if you remove the capacitor it's still going to be a safety issue. Side note: input capacitors are not specifically a 'vintage' thing. X2 EMI suppression capacitors are still fitted to new equipment, and have none of the safety issues you suggest. So long as you don't tie neutral to the chassis, you'll be fine.
I noticed the schematic with the ' drawn ' plug is not a good picture. It shows the neutral side connected directly to ground and the capacitor going across the two power leads.
Hey there, ran across this video in my search on how to properly wire up a vintage television set. This is great information and I am glad to have learned it. Thanks for the video!
Unfortunately, your drawing is wrong. You already have a full 120 volt AC connection to ground ! If the bottom plug prong of your AC plug is inserted into the hot side of the outlet, which is a 50/50 percent possibility (1 out of 2 odds) you already have 120 volts hot on your chassis, mic or guitar regardless of the condition of that capacitor! (See 4:52) The danger of a cross-the-line cap is not a short to ground but a short arose the AC outlet causing a potential fire hazard if the fuse / circuit breaker is slow to burn / trip, respectively.
I learned early about capacitor discharges. When I was a child I pulled the plug of our family's color TV out of the outlet and touched my tongue to it. It shot a 12" purple arc down to the corner of the floor. After sitting motionless for a few minutes I realized I shouldn't have done that but was fortunate that I didn't hurt myself. I never did it again.
That would have been some 17-35kv stored in the anode of the screen in those old sets, that must have backfed through the AC plug. You became a grounding rod, and something metallic near the floor help dissipate the charge. You're lucky, albeit low amperage in that discharge, definitely not fun getting snapped at with that much potential. 📺⚡👈😲
Great video. Here in Australia, I believe we've always had 3-prong mains outlets. Well since it was codified in the 1930s, anyway. I just can't imagine ever connecting a neutral mains to a chassis. And I don't believe I've ever seen any gear, vintage or otherwise wired that way. AFAIK our plugs, still in use, were copied from a now obsolete (3-prong) American design. I wonder why the US ditched the earth prong?
yikes excuse my ignorance but what is this ugly Frankenstein of a piece of electronic gear?!?!?!?!!?! it looks like a nightmare to work on like a kid somehow made it
Recapping the second 2d30 preamp right now. This one is a little different than the first and the schematic. 2 different capacitors in this one than the schematic has.
As a 16 yr old playing guitar on an old Ampeg V4 Guitar Amp, which a previous owner has stupidly pulled the 3rd grounding plug out of to fit into 2 prong outlets, this capacitor saved my life.
I remember actually throwing my cousins electric bass guitar because as soon as I touched the strings wow what a jolt lol take 73 ve3hip Mike from Welland Ontario Canada 🇨🇦
Thank you, another great informative video! Coming from the guitar amp building world I've removed my fair share of deathcaps and always went with option 2 (I always would offer the removed parts to the customer and usually they didn't want them, and many of them are vintage bumble bees in good values for guitar tone pot cap if they're still good). It's good to know there are other considerations now that I'm delving into audio stuff and #3 looks like a good option for vintage gear.
Great explanation video. Wouldn't your example at 4:00 however, be putting the hot side right to chassis ground if plugged in that way?? From my experience non polarized plugs were the norm easily into the 60's when a lot of this stuff was made so that means one expected a tingle at the mike then??? All homes etc. would have had outlets that weren't polarized ( mine still does). Or was the expectation to make sure it was plugged in correctly on the user?? I am working on a 1939 GE radio with an AC transformer power supply. It follows your basic amp power supply schematics with a 5y3 rectifier tube. However, it uses a double capacitor connecting both hot and neutral to chassis. It wouldn't matter which way this is plugged in but then typically one isn't touching the chassis on these units. The back is open open with the chassis though. They were covering both sides with a filter as it could be pluggeg in either way????
Wait... if we simplify the scenario by removing the fuse the cord from the equation (assume it's already been replaced with a polarized one), we just need to remove the death cap and replace it with an X/Y safety capacitor? Example: My radio has the death cap coming from the 35Z5-GT pin 5 to ground. So, do I just replace it with an X1/Y2 safety cap and that solves the problem?
All excellent information ! I prefer to replace the line cord with a polarized line cord. Would it also be wise to replace this cap with a new one if its over 20 years old?
how about replace the death capacitor with a new one so its time to failure is now not so soon and use a gfci circuit to power the unit only. Then if the capacitor fails instead of getting a shock, the gfci will trip instead.
Your sample reactance formula at 9:00 had a slight error. All but the first term belong in the denominator. Here I also show the conversion from uF to F. 1 / (2 * 3.14 * 60 Hz * .05 / 1e6 F) = 53 k Ohms
Actually, the black caps are made of paper and plastic. And, back in the 50's they had a reputation for high failure rates. And hence in this method of noise reduction they got the name of "Black Beauty of Death". I can vouch for being hit with both 120 and 480 (not direct). And I can tell you it's not fun. Do your home work. For metal chassis and anything you have to hold in your hand that has a ground reference, replace that un-polarized cord with a polarized cord. And replace the black beauties with something that has a higher safety rating.
This is why my Dual 1229 euro spec will pop at start and stop.? Actually had a Dual 1218 that the motor would only have enough power to get through the start cycle if the plug was in a certain way. I had one of the plug prongs colored red with a sharpie. Thank you for posting this! Took me 5 years to stumble across it but I knew something weird was going on in these old Dual turntables.
Thought I would post this, maybe you might pin it? Speaking of vintage stereo cords... I was curious about these non polarized plugs on these old cords, and I found this over at Steve Huff... "1. Power outlet: As you know these older devices do not come equipped with a plug that has the wider prong to identify it as being grounded. Nonetheless, it is important to pay attention to the orientation when you plug it in. The way to identify which way the plug goes in is by feeling the power cord. One side of the cord is completely curved and smooth on the outside while the other side of the cord has an edge. The side that is smooth should plug into the wider prong on your wall socket." I checked my Sansui 4000 power cord, and sure enough, there was a protrusion/edge on the cord that ran the entire length, and the other side was rounded. I probably knew that from years ago, but have long since forgotten.
How about the millions of AC/DC radio sets & TV sets with the straight line fed series heater strings for the tubes? Some of these had all metal cases with an unpolarized 2 prong NEMA cord or early early radios had a screw shell Edison base adapter for a common old time light socket. There are two schools of thought on the Y rated disc cap. Use a Y rated cap and hope it fails open or use a Z rated cap and put a GDA 50mA rated fast blow fuse in series with it. With two wire zip cord or lamp cord the side with a single rib or multiple ribs molded along the extruded insulation is always SUPPOSED to be the neutral. The smooth insulated wire is always SUPPOSED to be the hot. Factories got this right most of the time. Some of these newer two wire zip cords have a white trace down the neutral side now.
I took my NAD 7400 receiver for repair, but the guy is having a hard time finding transitors/capacitors repalcement. Can you suggest a place where to buy those components?
My Kustom Kasino amplifier had a toggle switch on the back to select which "neutral" went through the death cap to chassis! I guess it was to correct for plugging it into the wall backward? I suppose if you heard line noise, you'd flick the switch to whichever position sounded better :| I rewired it with a modern 3-prong plug-end cord AND installed a line filter module inside the chassis. I left the toggle switch there but not connected to anything. Any future owner of the amp can play with it all they want ;)
My grandparents had an old combined record player/radio cabinet from the 1950s and my grandad had marked with nail polish on the plug end Red facing up was wrong and Green facing up was correct, if it was plugged in the wrong way the record plate would spin so fast the vibration would make the cabinet move across the floor! It was sending 120V straight to the motor lol
Ok so question. I have an old peavey deuce and it appears to have a "death cap". The schematic actually calls it a DVL cap and from what I can find maybe this is some sort of safety cap? Anyway the question- the value of the cap is 0.022 uF and I have not found any non surface mount style that have that value. Can I use a larger capacitance value cap?
23:45 - sushi stick - it could help drive elevators while in covid state of socialism :) I like your explanation of how the guitar strings are installed it has finally explained to me - after 30 years - why did "young einstein" movie had that scene with electric guitar shock :) - earlier i thought electric guitars are insulated.
Not try to connect more than two unit with unbalanced interconnets and its gets not as fustrating as it looks. Need one point to grounded and one floating on interconnect ground with bypassed RF to the safety ground not to the Line/Null conductor. More then 2 units: use balanced interconnets and prooper connections to safety ground on all units. In a case of 2 original vintage unit the capacitors are can be keep on a Null conductor, with an leakage test.
I don't understand electricity. As a kid we had an old briefcase style turntable from probably the 1950s. If we touched a certain part we used to get a shock. We used to dare each other who could hold on to it the longest.
Actually even older, unkeyed power cables have indicators to show which pin goes to neutral. Its the rib or stripe on the wire that goes to neutral IIRC.
I find it interesting that the EICO HF-85 in your video did not have a fused AC input. I "built" an HF-20 (my first kit that required soldering) in 1959, which HAD a fused line (2A). It was a GREAT 20 watt MONO amp AFTER I had a local "radio/tv shop" (remember those?) fix a "COLD SOLDER" joint for chassis ground! I was using a Weller soldering gun (remember those?), not enough heat for good solder flow. The guy that owned the shop "fixed" my amp for FREE, took him about 5 min to find the "problem". Assembling that kit jump started my carrier as an electronic tech for the next 40+ years!!
How about adding a neon light (plus resistor) to the 3 wire plug. The hot lead to the fuse, the neutral to the to the transformer and the neutral to a 220K resistor connected to the neon lamp and the other side of the neon lamp to the green wire. If the socket is mis-wired the neon lamp will glow- danger warning!!!
Yes, I discovered those when I was 8 yo. I got many a shock, and introduced my friends into the fun. Most are still alive and no one got electrocuted. I don't work on radios that old anymore so I am going to play hooky from class. Toodle-oo.
Why isn’t the solution to ground loops a ground lift switch? If the sat box connection is causing a ground loop lift the ground connection of the signal wires connecting to your hifi stereo. If it’s only grounded on one end it can’t create a ground loop and your equipment has a safe connection to earth. You can even make it a ground lift box separate from your hifi so you don’t have to mod the vintage hifi w an offensive switch. In that case the box would share a ground w your hifi while the input to the box is isolated allowing you to use a switch to either share or not share grounds w the sat box. Your explanation and deference to those hifi guys makes it seem as if no other solution exists or another solution would be so arduous and onerous that it’s not even mentioned. Ground lift is the understood long time industry solution in recording studios etc and deserved a passing mention in this video.
so to be clear, death caps are only there for two prong plug amps. if my amp has been converted to three prong with ground, or i want to do a conversion myself, the death capacitor is not necessary ? and any possibility of shock is eliminated?
You wouldn't think a cap would have enough energy to be fatal. A 200uf cap at 400v only has 16j of energy. Plus assuming a skin resistance of 10kohm, the time constant would be 2 seconds, so it would take 10 seconds to fully discharge. And that's just DC, which isn't going to disrupt your heart as much as AC, but can cause burns. I know this last bit is far fetched, but if you're just handling the cap, the current would have a pretty short path through your body, not through your chest. That's not to say there's no danger. I have no doubt deaths and injuries happen from caps. The risk just seems overstated. Be safe.
Mark, FWIW, I have SO many screen shots of pieces and parts of your videos that I feel like I should make a separate folder called “Mark’s Masterpieces”. Your detailed explanations are so very appreciated, and I’m sure I’m not just speaking for myself as far as the appreciation AND screenshots! So glad you seem to be doing better too. There’s a lot of people who care about that southern drawl of yours!
You would hear about musicians being electrocuted back in the 1960s. The UK has 250 volts mains. It was often said that musicians disconnecting equipment or changing instruments was the cause.
Yep, we have 240v mains here in Aussie land as well. You don't even want a single amp running through you at that voltage! Kicks like a bloody horse! Luckily we have had 3 pin plugs for a very long time now! I used to boggle watching movies from the US and seeing just the 2 holes in the wall that they had up until at least the 80's! I guess the safety margin is a little more when you're only dealing with 120v! The main problem around here is earth hum from everything being connected to the same ground rail, but ground lift transformers between equipment on the signal cables usually does the trick without compromising safety. Probably lucky that all 4 of the beatles even made it through the 60's though huh?
@@ballsrgrossnugly It appears you have no training in the electrical or electronic industry, nor a lot of practical experience, to post such deluded comments. Understand this perhaps: 1a. Less than 1 amp, in fact far less current is sufficient to kill you. NO fuse will afford such current limiting protection. Note that RCD [aka Safety Switches] are designed to detect 'earth leakage' fault conditions where that 'leakage' maybe though a person to Earth/Ground. The 'trip value' typically is fixed at 30mA... in medical facilities this can be as low as 10mA. 1b. 110V or 240V... [even 415V] is considered Low Voltage in Australia, and it is the current flow through YOU that kills at these voltages. Yes.... a 240V A.C. shock hurts... so does a 110V, 415V and 660V belt. Above 240V it tends to burn deep. Nothing funny about it. 2a. Australian 1phase mains voltage plugs come in both 2 and 3 pin formats. Even so, get some DIY = DIE moron connect either the socket or plug the wrong way, or terminate at the appliance the wrong way and that assumed 'polarity' [this is A.C. remember... not D.C.] render a single pole switch in the appliance not effective in isolating the ACTIVE [Hot] line from the appliance. 2b. Australian General Purpose Outlet Mains Sockets and Plugs have a pin configuration that has an inherent 'polarisation' being in the / \ profile... the / pin is Active and \ Neutral. Round pin plugs are reserved for Special purpose [lighting] applications. The U.S. looking | | are only used for Extra Vow Voltage A.C. applications. It's stupid to bend / \ pins to fit in | | sockets sometimes found at the rear of Amplifiers etc. 2c. Be it 120V or 240V A.C. your "guess" is VERY WRONG. Either voltage system has potential enough to facilitate sufficient current flow through a human to KILL ... NO 'SAFETY MARGIN' APPLIES. 3a. The 'Earth Hum' you mention has NOTHING to do with the way Earthing wiring is mandated in accordance to Australian Standard Wiring Rules [M.E.N. system used], rather it has EVERYTHING to do with Ground Loops between audio equipment. 3b. 'Ground lift' is not done via use of 'Transformers'. It is achieved in audio gear by use of an appropriately rated circuit using a Bridge Wave rectifier, resistor and X1Y2 capacitors when both Ground and Earth circuits appear in the same appliance, ya dill. Ground loop 'Hum' can appear between different components in a HiFi setup OR within a single piece of equipment. Frankly, I cringe at the thought of ever encountering a piece of equipment you have laid your hands on, given the demonstrated lack of these very basic electrical / electronic principals. God help anyone that might use equipment you have worked on or their innocent kids. YOU are an example of why such work requires qualifications and Licensing in Australia... TFFT. GET AN EDUCATION prior to dispensing advice in the future and limit your handywork to extra-low voltage [under 32V] stuff.
@@BTW... I think you need to read my comment again, realize you have no idea what you're talking about, and shut up. Cheers. EDIT and man, did you write an essay about stuff I already know because you apparently think you're smarter than everyone... here's a hint: Googling stuff to copy into a condescending comment only makes you look like a dick.
Where does this come from these 2 prong cords are polarised you cant plug them in wrong. Ive worked on thousands of these. Non polarised cords had a transformer and had no cap to ground. I have never seen this....it would not pass UL certifications exactaly what brand and model are you talking about
I'm a little confused. At 6 minutes your schematic shows the death cap between hot and neutral. At 12:05 the schematics show the death cap not going between hot and neutral... rather from one or the other to chassis. Aren't these completely different?
Hi Anthony - your confusion is right. The first schematic shown is actually NOT representative of how a death cap is wired, nor of how it functions. This first schematic is representative of a manner of ‘shorting out’ high-frequency noise by using a capacitor across the feeding lines. A death cap would actually work between the neutral line and chassis ground, again ‘shorting out’ high-frequency noise on the power-line to ‘earth’; this ‘earth’ being represented by the device chassis, in the absence of a real ground reference.
@@petervanvelzen3116 Thanks Peter. Does that mean that if I have an old audio device which is wired like the first schematic, I should not only replace that cap with a safety rated one, but also move it to look like the second schematic?
A standard GFCI in the USA trips at about 5mA mismatch of current; the video shows that the capacitor in the example calculation only had about 1/2 of that current flowing. So the standard design is not going to be sufficiently sensitive. But if one were to carefully modify a standard device to increase the sensitivity, one could embed that into an extension cord of some sort, and only power devices with that. Lots of trouble to do that when an easier solution is to just use a polarized plug on the device in the first place.
Hi Mark, I have 2 Dynaco ST-70 , that don’t have the "Death Cap" ... I have replaced the supplied power cord with a 3 prong IEC Male socket. Should I add the CAP into my improvement, because the original circuit diagram does not have this CAP Filter? Thanks
The "All American Five" table radios had those. And if the plug was reversed, you'd experience a weird "fuzzy-tingly" sensation if you brushed against the cabinet.
When I was a kid, we had a GE tabletop radio I was SCARED TO DEATH OF because my Dad happened to be grabbing the coffee pot one morning, brushed against the radio, and jumped back so far there was coffee all over the kitchen!!!
I just purchased a 1936 Philco Model 650 console radio. I checked the schematic and it actually has two 0.015uf death caps. Each leg of the incoming cord has a cap to ground. Of course the pug is original and not polarized, so I guess you could say it’s double death capped? 😬I’m going to try installing a new cord with ground, and remove the cap on the hot leg.
Great summary of the purpose and fitting of those filter capacitors. Over here in Europe, many of our countries have symmetrical power outlets and connectors, so here we really have to double check the polarity manually if we have equipment like this. Some countries do have polarised plugs, notably the UK, Ireland and Denmark. A few others do also have asymmetrical contacts. However, not all of those have a standardised polarity order. The many that use the German Schuko style symmetrical connectors have no option but to check for the polarity. I usually try to do that for equipment that do have a marked polarity. It is worth noting though that this has been a known fact for basically ever, and equipment _should_ be designed to work in a safe manner regardless of the polarity of the connected power (not always a given, especially not for homemade or vintage equipment).
I am ordering parts to rebuild an HF 85 as you have done. I have been thinking about adding a fuse too, because the transformer was bad and I had to have one made. (Heyboer) The receptacles on mine are cracked and not polarized, I am thinking about removing them and installing blanks from the inside. I would then use a lug strip to make connection. Switched receptacles don't seem to have mush use in today's HiFi.
The other problem with these capacitors is that they can fail catastrophically without warning when you go to plug the device in after a long period of disuse!
And by catastrophically he means converts volts to smoke and flame and probably a cloud of the substrate they used in the cap that has been violently heated and ejected. While also possibly causing spikes that can cause a cascade effect and blow even good caps on the board! (among other components)
That (exploding old cap) happened to me with a very old HP audio frequency signal generator. One of the variations of the model 210, if I remember correctly. It was from about the 1960's, I think. Plugged it in about 15 years ago. It went BANG and let the smoke out.
I have a vintage Heathkit solid state amp with 2 .05uf 1400v ceramic death capacitors. I temporarily marked the hot side on the plug. Now I am going to swap out those caps with safety caps per option 3 and install a new cord with a modern 2-prong plug.
On old amps (music or hi-fi) which use the chassis to complete circuits you really should find those points (ground wires screwed into or soldered to the chassis) and modify them so that they all connect to a "star" ground insulated from the chassis. Then you can use a modern 3 wire plug. Also removing those old style ground points will also eliminate the chance of high voltage getting to the chassis through them in the case of a capacitor failure other than the death cap. The green wire on the plug is really only there in case some high voltage hot wire comes in contact with the chassis due to say a solder connection coming loose on a high voltage line. Removing any part of the amp circuit that uses the chassis as a conductor eliminates even the possibility of high voltage getting to the chassis. Also before you work on any older amp that uses high voltage you should test for high voltage on the chassis using an AC voltmeter in case you have an amp that you've never seen before that may come to you with a high voltage already getting to the chassis for whatever reason (somebody messed up or a wire broke loose-whatever). Also those multiple ground wires to more than one point on the chassis can develop corrosion and cause all kinds of hum due to one ground point being clean and another having resistance due to corrosion or loose connections. I really would never feel safe around an old amp that doesn't have a 3 wire plug and I've been playing and working on tube amps since the sixties. Before I play an old amp I always check for a grounded plug and ask the owner if the death cap has been removed. I know everyone wants to keep things "vintage" but all these mods if done properly could be reversed back to factory if someone insists on keeping an amp in a dangerous config. Personally I wouldn't feel comfortable working on anybody else's equipment if they wanted to keep it in an unsafe config. If that person gets shocked or injured and you worked on the amp you could be liable if you knew the mods should have been made but you didn't do them for whatever reason. My dad started out as a radio tech in the Navy and he always joked that the good high voltage techs were the ones that were still alive. I took that lesson very much to heart. Remember that high voltage is always looking for someone to kill and that's no joke!!
The term has colorful origins. We tip our hats to the Irish for 'kaibosh' (caidhp bháis), which means "death cap", the hood put on someone before they were hanged to death.
Blimey, I may moan about our huge three-pin plugs here in the UK, but this video really brought to mind how much safer those plugs are - even with double the voltage of the USA!
If you install a 3 prong cord wouldn't that keep you from plugging it in incorrectly and that alone would keep the death scenario from occurring? And if you install a three prong cord, the added ground would take any sort of short to chassis directly to ground and trip the breaker. I'm not understanding the need to remove the death cap if you install a three prong cord correctly.
