0ct0Pr0n
Tele-Meister
Which amps have death caps? Can they be discharged with one of those honking ceramic resistors? I read that they can be deleted/replaced, if so, what was the point in the first place?
Can someone give me a quick rundown on the "death cap?"
This should explain it all: https://robrobinette.com/Death_Cap_and_Ground_Switch.htm
NoTeleBob
Poster Extraordinaire
Yeah, the RobR article covers it in detail. But bottom line, if your amp has a two wire cord and a "ground switch", replace the cord with a properly wired three wire cord and just disconnect the switch from the circuit.
Just right. Rob's article is a complete discussion, and tells you how the death cap worked, why it's not a safety feature, and how it can kill you even if you wire it to a 3-prong cord. FWIW, re discharging, the term 'death cap' may suggest it's the cap that really needs discharging, but no, in old and modern amps the caps that may store lethal charge and need discharging are the filter caps.
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Which amps have Death Caps™? Look at the schematic. If there's a cap on the line side of the power transformer, that's your Death Cap™. A polarity switch is a dead giveaway that the amp has, or had a Death Cap™ The cheapie transformerless amps of days gone by don't have Death Caps™, but they are Death Amps™. That's another subject altogether.
Can they be discharged...? It's a very small cap across an a.c. source, so it doesn't hold much of a charge. No need to worry about discharging it.
I read that they can be deleted...? Yes, just cut the thing out of the circuit.
Why...? Read Rob's writeup linked to above.
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In any discussion of Death Caps™ I always note that removing the cap is only part of the operation. You must also replace the line cord with a good quality three wire cord, and use the amp with a properly wired outlet that actually has a good ground.
Can they be discharged...? It's a very small cap across an a.c. source, so it doesn't hold much of a charge. No need to worry about discharging it.
I read that they can be deleted...? Yes, just cut the thing out of the circuit.
Why...? Read Rob's writeup linked to above.
--
In any discussion of Death Caps™ I always note that removing the cap is only part of the operation. You must also replace the line cord with a good quality three wire cord, and use the amp with a properly wired outlet that actually has a good ground.
Lowerleftcoast
Poster Extraordinaire
In addition to the information on Rob's Death Cap site...
The *Death Cap* is not the only cap in an amplifier that can result in a potentially life altering shock. The filter capacitors in the high voltage filtering circuit can store voltage and be a shock hazard even if the amp is not plugged in for an extended period of time. These are the caps that should be discharged with one of those "honking ceramic resistors". Actually, the resistor doesn't have to be huge. A 100K one watt resistor will due. The reason to use the resistor, for discharging a cap, is to keep from making a spark.
Another thing to know... The filter caps will recharge after they have been discharged, even without any power being supplied to them. They will not recharge to the same voltage they had before they were discharged but it may be enough voltage to shock the unsuspecting shock brother. Use a multimeter to determine the voltage is at a safe level whenever working on the circuit.
The *Death Cap* is not the only cap in an amplifier that can result in a potentially life altering shock. The filter capacitors in the high voltage filtering circuit can store voltage and be a shock hazard even if the amp is not plugged in for an extended period of time. These are the caps that should be discharged with one of those "honking ceramic resistors". Actually, the resistor doesn't have to be huge. A 100K one watt resistor will due. The reason to use the resistor, for discharging a cap, is to keep from making a spark.
Another thing to know... The filter caps will recharge after they have been discharged, even without any power being supplied to them. They will not recharge to the same voltage they had before they were discharged but it may be enough voltage to shock the unsuspecting shock brother. Use a multimeter to determine the voltage is at a safe level whenever working on the circuit.
NoTeleBob
Poster Extraordinaire
Alternative thought: after you take out the death cap and rewire the power cord, wire up the switch for something fun! You know like LEDs in the speaker cabinet or just put a red pilot lamp on there somewhere and tell people it's a super boost sound enhancer. Turn it on when the band starts to get loud and then just go back to playing.
0ct0Pr0n
Tele-Meister
I'm fairly handy with (simple) component-level electronics, but I'm certainly not about to open up a vintage tube amp on my own. I'd just seen it come up in various places and was curious what the deal was.
Heh, yeah, it could be fun to ask your friends to flip the (disconnected) ground switch and notice the obvious difference. More usefully, I've found that switch hole a handy location for a pot or switch that does something. Yes, it's in an AC zone, but I use shielded cables if the mod involves signal, and I've had no problems.
Telekarster
Poster Extraordinaire
I thought the general rule of thumb was that if it has a 2 prong cord, it has a death cap. Is this not entirely true? I'm not an amp tech etc. so forgive my ignorance in advance 
Well, at a minimum, there're 2-prong widowmaker amps out there, which is a whole 'nother kettle of electrified fish. And some 3-prong amps (eg, conversions done by vintage-as-possible freaks?) may dangerously retain the death cap, as Rob points out, so the 2-prong = death cap rule may fail in both directions.
Finally, some layouts (Mojo, in years past) kept the death cap for appearances but IIRC didn't wire it into the circuit. Is an inactive death cap a death cap? If a tree falls in the forest...
Finally, some layouts (Mojo, in years past) kept the death cap for appearances but IIRC didn't wire it into the circuit. Is an inactive death cap a death cap? If a tree falls in the forest...
I always remove the death cap when convenient to do. But to tell the truth, I think it's a lot of bruh ha ha being stirred up. I have NEVER heard of anyone being shocked much less killed from the Death Cap. Maybe someone did once.....?
Of course we used to play outdoors and indoors with 2 prong cords. And when 3 prong came out many places only had 2 prong outlets in the building so we used adaptors. Now yes, .....you can get a good shock outdoors or with multiple 2 prong devices plugged in, some backwards. Still....... we just did it. Yet....I'm sure someone must have been killed in the last 70 years.......
I guess I'm just saying it's a bit blown out of proportion......... I laugh when I see someone say "Dont turn that amp on until it's rewired with 3 prong!"
Get off my lawn!
Of course we used to play outdoors and indoors with 2 prong cords. And when 3 prong came out many places only had 2 prong outlets in the building so we used adaptors. Now yes, .....you can get a good shock outdoors or with multiple 2 prong devices plugged in, some backwards. Still....... we just did it. Yet....I'm sure someone must have been killed in the last 70 years.......
I guess I'm just saying it's a bit blown out of proportion......... I laugh when I see someone say "Dont turn that amp on until it's rewired with 3 prong!"
Get off my lawn!
schoolie
Tele-Afflicted
Anybody add death caps to modern amps, just to keep practice interesting?
Sadly, drum kits don't have a spot for a death cap...
On a more serious note, regarding death and stuff, it's true there's some debate about how Keith Relf died; amp electrocution may or may not have been the whole story. Recall he was on British power at 240. "Relf died in the basement of his home in 1976 at age 33 from electrocution while playing an electric guitar. He had had several health problems throughout his life, including emphysema and asthma. He may have been taking the medications commonly used to treat those diseases at the time, and these may have contributed to his inability to survive the electric shock."
Although Rob notes no electrocution has been *conclusively* linked to the death cap, he also points out that even in the US, if it fails as a short it'll put 125 @ 15A on the chassis, guitar bridge, and strings, which is plenty to kill you.
Also quoting Rob, and noting again that wrongly-wired outlets are common in the US: "I strongly recommend replacing all two wire power cords with three wire cords with a chassis ground. I also recommend disconnecting or removing all death caps because they can be an extreme shock hazard if a three prong power cord is plugged into an improperly grounded power receptacle."
On a more serious note, regarding death and stuff, it's true there's some debate about how Keith Relf died; amp electrocution may or may not have been the whole story. Recall he was on British power at 240. "Relf died in the basement of his home in 1976 at age 33 from electrocution while playing an electric guitar. He had had several health problems throughout his life, including emphysema and asthma. He may have been taking the medications commonly used to treat those diseases at the time, and these may have contributed to his inability to survive the electric shock."
Although Rob notes no electrocution has been *conclusively* linked to the death cap, he also points out that even in the US, if it fails as a short it'll put 125 @ 15A on the chassis, guitar bridge, and strings, which is plenty to kill you.
Also quoting Rob, and noting again that wrongly-wired outlets are common in the US: "I strongly recommend replacing all two wire power cords with three wire cords with a chassis ground. I also recommend disconnecting or removing all death caps because they can be an extreme shock hazard if a three prong power cord is plugged into an improperly grounded power receptacle."
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Well, at a minimum, there're 2-prong widowmaker amps out there, which is a whole 'nother kettle of electrified fish. And some 3-prong amps (eg, conversions done by vintage-as-possible freaks?) may dangerously retain the death cap, as Rob points out, so the 2-prong = death cap rule may fail in both directions.
Finally, some layouts (Mojo, in years past) kept the death cap for appearances but IIRC didn't wire it into the circuit. Is an inactive death cap a death cap? If a tree falls in the forest...
I've learned to answer this useless postulate with "how do you know it fell?" Which leads me to giggle at the idea of a cosmetic death cap sitting in a chassis and soldered to isolated lugs. People can be silly!
I don't have much input on the technical side here, I know enough to literally be dangerous, and happily let my tech perform the safe repair of a 3-prong and no death cap cause not everything vintage is necessarily good, much less better.
Uncle Doug uses the switch for a negative feedback loop.
Telekarster
Poster Extraordinaire
Man.... I never even heard of a death cap until I began hanging out here LOL!!! Then I started to kind of freak out cause I can think back on all the times we played with 2 pronger's in all sorts of conditions. Heck the house I grew up in only had 2 prong outlets, and very few of em at that, and still had glass fuses! Just like the scene in Christmas Story.... yep... had about a dozen things plugged into 1 outlet. Sometimes sparks flew, fuses blew, etc. but no one worried about any of it... to think back on it today freaks me out, but maybe I'm a victim of modern hype?
Or.... maybe we just weren't that smart back then? 
magicfingers99
Friend of Leo's
its mostly older amplifiers stored in damp conditions. Look for this..
death cap, don't pick it,don't eat it. try not to even look at it.
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