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.

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

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!

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

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.

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

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.

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

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!

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

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

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

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

"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.

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.

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

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.

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.

Thank you Mark! Great information and clearly presented!

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.

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.

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

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!

Great video. Commentary, a little theory then application on the bench. Thank you.

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

Just discovered this channel. Very informative and clear explanations!

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!

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!!!

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.

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.

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.

Now I understand after all these years! Thank you!

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.

Great explanation on this, I needed that thanks!

I just ran across this video and I like it. Thank you.

Excellent video and well presented. Thank you.😊

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 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!!

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.

Awesome as always!!

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.

Thanks for the precious information! Wil ground my old stuft or replace the capacifators!

Fantastic series man.

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.

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.

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

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?

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.

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.

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.

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.

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?

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.

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.

Excellent tutorial.

Could you do video on suggestions for avoiding "ground loops" when interconnecting components in an audio system, such as a bi-amp setup? The relatively low "difference" voltages due to ground loops CAN have VERY EXPENSIVE consequences to solid state equipment! Been there done it! I would like to know what you would recommend as far as "bonding" the chassis to avoid these loops. THANK YOU!

Does this work to block interference then? Would it be possible to add a death cap and the smallest possible fuse in series to the negative wire of a three prong cord and be completely safe? Upon capacitor failure the fuse would blow?

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.

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!

Great public service, thank you.

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.

Well done Mark!

😆 we worked with Capacitors made in Beer Barrells on major aerial sites! Packed a heavy punch for sure 😝 Happy days 😆

Awesome resource you have here mate! Learning a lot watching these vids. If you happen to see this comment, quick question: With method 2, wouldn't it just be possible to use the 3 prong plug with a regular death cap going to the green wire from the neutral? That way if it fails to dead short, you get the same effect as the fail open caps meaning there will be earth hum but eh amp is still safely earthed to the ground of the house wiring? (assuming the house is wired correctly of course!) Just wondering why this isn't an option? If if isn't one? Cheers.

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

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

Man excellent video!!

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?

Thanks for the info man

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.

Thing is, if you don't earth the chassis of any piece of equipment, you are relying on the braiding of the signal lead interconnects to carry any fault current, from the unearthed chassis to ground via the equipment that is earthed. It may not be able to carry sufficient current to trip the breaker. So, it's not a great scenario, but I see the audio issue with old kit.

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!!

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?

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.

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

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.

Thank you Mark for another great video! What size of fuse would you installed in this unit, a 1 Amp slow blow fuse will it be good?

I'm glad we have safety capacitors now. I'm seeing most vintage restoration techs changing to a three prong AC cord.

There's something hilarious about how designers of older tech never once considered consumer human error as a factor when making electronics

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.

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?

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

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 🇨🇦

Quick question: any thoughts on substituting a y-capacitor (as in the 3rd approach) with a polypropylene cap?

what is a ground loop problem? does it cause its own shocking hazard? or is it feedback noise problems?

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?

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.

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.

Thanks for the death cap explanation Mark, well done. (Aside Question) about the demo unit you used. I noticed on this unit and others as well that the rectifier tube is mounted at an angle (As with others, the socket for the tube is mounted into a tab of metal that is bent down into the chassis). Wondering if there was an electrical reason for this or if it was just a height issue. Cheers, - Eddy

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?

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 😁

This is totally off topic of the "death capacitor" and I apologize for that. This is a Great video by the way, I still haven't finished it but I fully intend to. I was poking around in my old 50 watt Marshall guitar amp years ago after it suddenly stopped working. It was unplugged, however apparently a filter cap got ahold of me a damn near threw me across the room! I have been shocked numerous times and have had some pretty bad ones through the years, but this was definitely one of the worst shocks I've EVER experienced. Thank God I was young at the time, I don't know if i could survive that now at age 63. I did get a similar one on a florescent light fixture that Was energized at the time. It's No Joke, capacitors can absolutely light you up like a Christmas tree whether the unit it is plugged in or not! This shock was so severe that it made a 20 amp/120 volt shock feel like a mosquito bite by comparison.

my 1978 Fender Princeton Reverve 2 amplifier has both the 3-wire cord and the switched filter capacitor...

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.

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

I had my head around this in seconds. The repercussions of death caps is indeed potentially death! Quite scary when you consider some older wax caps etc do often dry out and go short circuit 😱

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?

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

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 ;)

Great video. Are the two outlets on the back polarized? Why not just disconnect them?