Dealing with the DEATH CAPACITOR in Vintage Gear

[@oldricky]

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.

[@100amps]

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.

[@alexx2389]

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!

[@larryak0z672]

Finally someone explained the death capacitor in a way I could understand. Thank you for the great video.

[@ChrisG4646]

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.

[@mikesradiorepair]

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.

[@dwoaks1]

Thank you.

[@offgridjohn871]

MikesRadioRepair I use 57-63 valve amps .. my fave being a 63 amped vt40. I use these amps regularly... probably should change some caps😂👍

[@Les3201]

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.

[@PopeyeKF4LBG]

We put capacitors in line on our fishing electonics for " noise" suppression. Interesting topic. Thank you for passing on your knowledge and wisdom.

[@UncleDoug]

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.

[@Blueglow]

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.

[@UncleDoug]

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.

[@ballsrgrossnugly]

@@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!

[@UncleDoug]

@@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.

[@ballsrgrossnugly]

@@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!

[@roygutfinski9991]

"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.

[@rogerbarton497]

Televisions were worse, they didn't have a mains isolating transformer and one side of the mains went directly to the chassis.

[@okaro6595]

@@rogerbarton497 That is just what hot chassis radios did.

[@dhpbear2]

I could never understand why those old AC plugs were NOT polarized!

[@michaelszczys8316]

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

[@rb032682]

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.

[@NickP333]

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.

[@dougankrum3328]

ZZzap...those old vacuum tube amps had 300-400 volts all over the place...

[@GiulioLuzzardi-xf1xo]

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!

[@GiulioLuzzardi-xf1xo]

@@dougankrum3328 Felt more like a cannon blast straight to the head.

[@NickP333]

@@GiulioLuzzardi-xf1xo Yeah, it’s brutal.

[@theevallded]

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!

[@glenmartin2437]

Thank you. As a chemist, I had to work on older equipment. The electronics people helped me deal with death capacitors and other safety issues. Thanks again. Happy New Year.

[@johnwhite6005]

Very good explanation Mark and I learned much from you today. Have a Blessed Week.

[@electronicsworkbench]

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.

[@bobboyle7629]

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!!!

[@barrymayson2492]

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.

[@alien_man1669]

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

[@ballsrgrossnugly]

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!

[@sstorholm]

@@alien_man1669 The rule is; one hand in your pocket if you know what you're doing, both hands in your pocket if you don't know what you're doing. :)

[@tmastersat]

They were polarised you could not plug it in the wrong way....one side os larger

[@barrymayson2492]

​@@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.

[@uptownphotography]

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

[@ChanceValentine]

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.

[@bruceferrero8178]

Thank you! I am about to rebuild a couple of Zenith 7d30 chassis and was going to research how do this. Perfect timing! Thanks again.

[@bruceferrero8178]

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.

[@user-su5sq5ib3i]

Your channel is simply amazing. I feel like you are my personal instructor on tube electronics. There aren't many people in my area to learn from

[@xsnowbird7710]

Thanks Mark! love your instructional/educational videos. I've seen others replace this circuit but now I understand why.

[@wdmm94]

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????

[@davedrezTV]

Thank you Mark! Great information and clearly presented!

[@ElectroRestore]

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.

[@DrBovdin]

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).

[@TheOzthewiz]

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!!

[@Fotosaurus56]

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.

[@6StringPassion.]

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.

[@kwinzman]

Thanks for the video! What I took away from this: I don't want to ever use old vintage gear to listen to music.

[@curtisgriffin7924]

Very good video explaining a possible dangerous situation. Thank you again for the videos Mark!

[@Daniel-it1dp]

So, just plugging in and trying to use old audio equipment can kill you unknowingly. Scary stuff given how retro has really made a resurgence.

[@mc.the_machine]

Sorry if you answer this somewhere towards the very end, but, it occurs to me that there is a potentially much better approach: use a safety capacitor to ground between ground and the chassis. That might not technically be code in the US, but obviously neither is doing that from neutral. It presumably is somewhat safer, because it doesn't have potential back current coming from neutral to the area, and for the same reason, it might actually reduce the level of interference that's possible. Since system should be electronically isolated from the transformer, there shouldn't be any particular safety issue from electricity in the device unless something really shorts to the chassis. I would expect it to prevent ground loops at least as much as the pass-through capacitor to neutral would. What do you think about that approach? The only drawback that I could see that I don't think is really a big issue is that you do have to add the three-prong cord to the device still, and, compared to fully grounding the device, it does mean that if something externally electrifies the outside of the box, you have a little bit less safety protection than you would if you fully grounded it. Thoughts?

[@briand2614]

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.

[@voxpathfinder15r]

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.

[@cat-lw6kq]

(Carson's Lab): has posted videos here doesn't advocate attachment a ground wire to the chassis either.

[@matthewsavin6486]

Another potential issue with grounding the chassis to earth ground is that if the neutral is also bonded to the chassis in any way (signal ground), you’d be violating electrical codes that dictate that neutral and ground can only be bonded in one place in your entire system, usually your breaker panel or your meter base. You’d create a ground loop in your house which isn’t ideal for safety. This is if I understand all this correctly..

[@SSJIndy]

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.

[@GeoffSims-d4j]

Many years ago I had a valve amplifier with a capacitor start for the special motor that it uses. The motor is a German Pappst type with a static stator on the inside of the outer rotor. The capacitors are hard to get hold of now, but having tried electrolytic capacitors and watched them fail, I managed to buy some paper capacitors, which solved the problem. I still have the recorder deck and occasionally run it to keep running it to keep everything going. Paper capacitors are known to fail, if not used from time to time. An electrolytic capacitor failing is very messy as it blows the end of the capacitor off. They do have paper in them but it deteriorates. We know them as leaky capacitors. Geoff G4GNQ.

[@oakmountainman7872]

Thanks Mark! Just the kind of depth I was looking for. Also, hope you are feeling better.

[@ER-yq1lc]

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.

[@dhelton40]

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.

[@SandersAmps]

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!

[@parochial2356]

Now, any advce on a the X cap versus the Y cap approach to minimizing noise? What about using both? Would an X1Y2 set up provide better noise suppression, especiall in a noisy enviornment?

[@1176hambone]

Fix the pin 1 problem and proper grounding scheme will work. If there are ground loop issues, fix them.

[@kwacz]

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.

[@thechuckster1971]

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.

[@makeminefreedom]

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.

[@bountyhunter4885]

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. 📺⚡👈😲

[@steveirl9414]

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?

[@a2phil]

Me too!! All I can afford is the "it lights up, but..." tube radios online (or told it works, but doesn't)... DE KE8NFK

[@squidkid2]

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!!

[@NickP333]

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!

[@soldiersvejk2053]

Very informative. Now I understand what is a low frequency filter!

[@SansNeural]

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 ;)

[@RobMods]

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?

[@wmrieker]

I don't get it. In the diagram, you have a 2-prong plug, one lead goes to chassis ground. The two leads go on to power supply and a capacitor in parallel. I would think if the capacitor was shorted or leaky, it would either burn or the circuit breaker would trip. How does that give a shock to someone touching the chassis any more than if the capacitor were working perfectly? Likewise if the capacitor were open?

[@genesmith4019]

What about the polarity switch on many music amps that switches the AC polarity to kill hum? Wouldn't that toggle select dangerous polarity?

[@JeffSmith03]

Now I know why when I tried to show my dad the old fridge in the basement shocks me bad when I grab the handle, I couldn't prove it! He unplugs it occasionally to de-ice, but that time had plugged it in correctly. Glad I didn't die in my youth. Also I like catching small errors in explanations: If your capacitor shorts, the capacitance does not go to zero but rather opposite. You said do the math with cap going to zero but the math shows that would approach infinite resistance and be fine. Obviously a larger capacitance is what allows more current to pass through at a given frequency.

[@anson22m]

I learned this the hard way about plugging in a 2 prong cord...One night I was up very late working on restoring a Jukebox....I forgot that it was still plugged in guess I should of just given up for the day and gone to bed....But I reached down to to pick up the amp and I instantly got lit up and had a death grip on both the amp and the side of the jukebox..I fought it for a long time trying to let go but I couldn't....I started to panic and then a calm just came over me as if I wasn't even being shocked to death anymore....I was able to finally realize I would not be able to let go and that I needed to unplug the Jukebox by dragging it and in doing so I dislocated my shoulder...Always unplug anything you are working on and make sure its grounded and plugged in correctly before touching anything on old equipment with 2 prong chords.

[@AnthonyPrechtl]

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?

[@petervanvelzen3116]

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.

[@AnthonyPrechtl]

@@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?

[@ph4z_]

Just discovered this channel. Very informative and clear explanations!

[@sstorholm]

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?

[@barry3400]

I may have missed it, but i didn't hear you mention what size fuse you installed.

[@tetrismk]

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

[@00djferni]

This problem does not affect equipment designed for the uk market if fitted with a 3 pin plug with chassis connected to the cpc.

[@Wil_Bloodworth]

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?

[@jenniferwhitewolf3784]

I should point out that 'Uncle Doug' DOES replace power cords with polarized-grounded 3 prong, 3 conductor power cords. In his 'famous' example, it is not possible to flip the plug! However, it is possible an idiot may have wired the outlet wrong, with a H ~ N reverse, which will then present danger.

[@gprojectnoob4779]

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.

[@vcp93]

Great video Mark. Hope you're feeling better. Take care.

[@JT-ei7qj]

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?

[@allanpatterson7653]

CRT is a good one I had a 35 inch RCA that the Xray circuit shut down leaving it charged very high. I discharged with a ground lead then pulled off the hi volt lead and it grew back enough charge to give me a good zap.

[@tonydfixertonydfixer9113]

There is a death cap on my 1980 pioneer sx590 home receiver/tuner/amp. If I do plug it in the incorrect position I can feel the current on the metal parts connected to the chassis. Kinda vibrates your finger or arm when sliding along the metal.

[@d46512]

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

[@TheLonesometoad]

I've been a musician since the 60s and I cannot count the number of times I received a nice jolt thru my lip from a hot mic. That's why most amps back then had a polarity switch on the back.

[@Subgunman]

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?

[@AtomicExtremophile]

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!

[@waynegram8907]

BLUEGROW, why do tubes get or what causes Getter Flash? The death caps are called X caps or Y caps but why do they call these capacitors X & Y capacitors that are on the AC line to ground to filter out AC line noises but not sure why they called them X & Y capacitors? The X & Y capacitors were made out of different capacitor material it seems to handle AC spikes and surges?

[@parachuteman4]

Great informative video. I have a an old Kay 703-C amp. One side of the 2 prong ac goes to the switch but it appears (i’m still learning how to read schematics) to go to an isolation transformer. The iso has a cap as well near it. My question. is that still considered a death cap With the isolation transformer in the circuit? And yes, it is labeled isolation transformer on the schematic.

[@isettech]

Most of the time when a band brings vintage gear to an event with a professional sound system, and the musician gets electrocuted on the microphone, it's because the professional sound system is entirely grounded, from the microphones, to the mixer, to the amp, etc. That vintage guitar amp was fine on a dry wooden floor. Enter a grounded metal object, and now there is a current path from your guitar strings to the grounded microphone. Doing house sound, all stage outlets are on GFCI. No exceptions. Yes musicians will complain their vintage gear trips GFCI breakers, so they can't use them. I've had to explain to musicians how their favorite surge protected and filtered power strip will trip the GFCI. Use our outlets without your filter to power your equipment here. We are not electrocuting anyone here today. You can buy a non contact voltage tester. Plug in your gear and check if the chassis is hot before touching anything grounded on stage. If your non contact voltage probe finds your amp is hot, don't use it until it is fixed.

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 😁

[@dsandoval9396]

My IT was telling me about some guy that died when he decided to take apart a PC power supply unit (i think) that had been unplugged for YEARS and still carried enough stored power to kill him.

[@JosephLorentzen]

At 12:18 the transformer, the variable resistor and the cap failing all look potentially problematic. Fuse please.

[@freddycookjr.2164]

GOT MANY ZAPS ON THE LIPS WHILE HOLDING GUITAR A SINGING BACK IN THE 70S KNEW NOTHING EXCEPT PLUG IN DRINK AND ROCK ON LOL

[@deadlotCamper]

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?

[@earlyeo8298]

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

[@tjules7]

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?

[@DrHarryT]

I don't know if it would work to use an isolation transformer??? 1st/ identify the affected units. 2nd/ install a 3 prong grounding plug ensuring it is wired correctly. 3rd/Make sure any receptacle you plug it into is wired correctly.

[@NCF8710]

An isolation transformer will eliminate the shock hazard from a hot chassis as it is no longer 120VAC above ground. It was standard procedure to use one when working on transformerless TV receivers in the 50's and 60's.

[@TheOzthewiz]

@@NCF8710 An isolation transformer is an ABSOLUTE NECESSITY when working on TODAY'S electronics that have "switch-mode" (transformer less) power supplies!

[@NCF8710]

@@TheOzthewiz Actually, switch mode power supplies have an isolated hot section which uses an opto-coupler for regulation feedback. The main electronic chassis is never connected to the AC line and is never live to ground like the old transformerless TVs of years ago were. There are only a handful of components on the hot side of a switch mode power supply (aka voltage to smoke converters). If you need to work on this section live, then use an isolation transformer.

[@DandyDon1]

2.3ma leakage would be enough to trip a GFIC. Also when dealing with old vacuum tube gear, the filament/B+ transformer has failing insulation inside which causes AC leakage of the primary to the chassis which creates another shock hazard scenario. A replacement power cord with a earth ground is thought to be a fix but it isn’t. It’s a poor bandage at best. This creates a low ever increasing dead short, which will become a fire hazard. Most AC circuit breakers are 15 or 20 amp. A fire can start long before it trips. You might want to share how to check for a leaky power transformer in vintage vacuum tube gear. To be absolutely safe a GFIC circuit can save you and your home.

[@DandyDon1]

BTW there are vintage vacuum equipment with a death capacitor tied to both sides of the AC line. Early Leslie amps starting with the model 22h forward until the practice was stopped. It’s been a practice to remove them when found, and not replace, as they have been proven unnecessary. Certain other vacuum tube gear has death capacitors like Hammarlund for instance.

[@AsurmenHandOfAsur]

Would a large diode on the neutral side of the cap stop the current flow if the cap fails? Or Maybe some other device that opens if the cap fails short?

[@SUPRAMIKE18]

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

[@tomcook5813]

What is a good all around cap to use replacing the death cap. Orange drop?

[@michaelwright1602]

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.

[@ronnierush9379]

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.

[@okaro6595]

You can buy an RCD that you plug into a socket so no installation is needed.

[@gearheadted9210]

Great video,wondering if you could share the part number of the XY cap,thanks!

[@Blueglow]

Ones I use are www.mouser.com/ProductDetail/Murata-Electronics/DE2E3KY332MA3BM02F?qs=sGAEpiMZZMukHu%252BjC5l7YQoLfzExQCX5T2uhDrRHizU%3D

[@jerrygarvey7257]

Thanks for the info , how do you know what side is positive and what is negative on those old capacitors, I have 3 in an old stereo unit that look like the ones in your video ordered 3 new ones from mouser they’re marked pos and neg. Don’t want to put them in wrong. Thanks for the help, jerry

[@finderskeepers5343]

I had a vintage stereo receiver from the 60s that began shocking me when i touched certain areas of it. Anyway, i was too scared to use it anymore and unplugged it. Don't know why it started to do that because the unit appeared to be in good condition.

[@analogblues9606]

Now I understand after all these years! Thank you!

[@garylowzik4740]

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.

[@ATeamAdam]

This is scary. I remember playing shows when I was younger. At certain venues we would get shocked bad when coming close to the mic. Some amps have a ground lift button that you can activate which in some cases seemed to help.

[@onemoremisfit]

A foam windscreen on the mic can also keep your lips insulated for addressing the mic while holding a guitar.

[@whitefordpipeshandmadebymi7238]

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 🇨🇦