The "Death Cap" - What is it?

[Archer993]

There is a cap installed between the ground and one leg of the fuse socket in many old amps from the 1960 — Valcos, Silvertones, etc.

People refer to this as the "Death Cap" and often remove it.

Does anyone here know why they remove it and why the manufacturer included it in the circuits to begin with?

Thanks

[SoK66]

It's usually connected between one leg of a grouynd switch on 2-prong vintage amps, and was intended to filter out buzz or hum in the line. It can short internally, putting full voltage straight to the chassis and potentially up the cord to you. Hence the term "death cap". On a 3-prong conversion the ground switch is eliminated, as well as the death cap.

[3 Chord]

Remove it when you upgrade to a three prong power cord. Wire it thru the fuse.

[Bones]

Tone is in the death cap, a lot of people don't realize that.

[SPUDCASTER]

Originally Posted by Bones

Tone is in the death cap, a lot of people don't realize that.

You'll need a good paper in oil one though!

[Archer993]

Originally Posted by SoK66

It's usually connected between one leg of a grouynd switch on 2-prong vintage amps, and was intended to filter out buzz or hum in the line. It can short internally, putting full voltage straight to the chassis and potentially up the cord to you. Hence the term "death cap". On a 3-prong conversion the ground switch is eliminated, as well as the death cap.

That was my best guess so thanks for clearing it up.

[6stringelectric]

I'm a bit confused here - since I have a 70's era Vibrolux Reverb that does have a 3 prong plug (I think from the factory, it was on the amp when I bought it, used, in the late 70's)

But, it also has a working ground switch, which I have often used.

So, would my amp have this Death Cap? I have always assumed it was safe, because of the 3 prong plug.

[SoK66]

Originally Posted by 6stringelectric

I'm a bit confused here - since I have a 70's era Vibrolux Reverb that does have a 3 prong plug (I think from the factory, it was on the amp when I bought it, used, in the late 70's)

But, it also has a working ground switch, which I have often used.

So, would my amp have this Death Cap? I have always assumed it was safe, because of the 3 prong plug.

Fender started installing 3-prong cords and 3-way ground switches in 1970, which was legally required. Because most homes & clubs, etc. had not been converted to 3-wire receptacles, Fender installed the ground switch. In the center position it was inoperative. In the outer two positions it functioned like the old 2-way switches, with a death cap. You were supposed to use a 3-2 prong plug converter in those cases, but inevitably guys just cut the ground plug off.

[rangercaster]

"it's a death cap, it's a suicide trap ... we better get out while we're young, because tramps like us ... baby we were born to run !!! " Bruce Springsteen

[Archer993]

Originally Posted by rangercaster

"it's a death cap, it's a suicide trap ... we better get out while we're young, because tramps like us ... baby we were born to run !!! " Bruce Springsteen

Thank You. NOW it makes perfect sense! It's poetry. LOL. (I hate using LOL)

[Archer993]

Question to all "in the know:"

Are there any documented "deaths" due to the "Death Cap." Any Attorneys here?

[CoolBlueGlow]

In my OPINION (per the forum rules :-) the real culprit for getting the pee shocked out of you is not the death cap, it is your non-polarized power plug, which was COMMON on death cap equipped Fenders and just about everything else consumer electric until about 1965. (Perhaps this is how the death cap got the bad rap?) If you have a polarized plug... even a TWO PRONG polarized plug, you can hardly put yourself at risk, since it is just about physically impossible to get the hot and neutral reversed by inverting the plug...because NEUTRAL is wide and HOT is narrow, and you cannot reverse them. Now, as long as that white wire in the wall goes to your chassis, you're pretty safe...and as long as your polarized two prong plug is wired correctly that's what's going to happen.

Once we put away the safety patrol rubber bumpers and think it through - that's all a three wire plug does under normal circumstances. It orients the polarity of the circuit and provides a safety spare neutral we call "ground". Once you plug in your uber-safe three wire plug with ground, guess what? Your so-called "ground" in that three prong plug is bonded directly to the neutral bus in your electrical box...just like the white wire. They go to the same darned place! The green ground wire is merely DEDICATED to being a safety ground (which is really just an extra neutral, in the real world of where the electrons flow in typical household 120vac single phase electricity)

So, back to the killer amp from h-e- double hockey stick. Exactly how can that non-polarized plug kill you? Easy - here's how it happens.

Let's say you have a non-polarized power plug on your vintage Grestch 6159 amp. In a hurry at the big outdoor beerfest/concert, you get the hot and neutral reversed by inverting the plug in the stage power box (Wide is neutral, narrow is hot - but, hey! With your Grestch's non-polarized plug you can put it either way!) Unfortunately, at today's beerfest, you've put it in backwards. You're still o.k. for the moment. You fire up your amp, grab your Tele, skronk a couple chords and all seems well. But this day, it's not. You step up to the mic, stick your lips to the grounded wire mesh grille of that SM58 and your fingers to the strings of your Tele, and get ready to wail! Unfortunately, your 120vac hot wire is connected to chassis - because you flipped the plug upside down! Now remember that your Tele's strings are connected right to your amp's chassis through the shell of the 1/4" plug. Today that chassis is connected to the HOT (black wire) of your AC supply. Guess what? Your chassis on your amp is hot - relative to the "real world" ground (NEUTRAL) of the SM58, who's wiremesh grille is connected directly through "shield" to the sound system console. Congratulations, your hand is the hot - your lips are the ground - your heart is the signal path and you are dead.

Two specific instances come to mind - A singer in some up and coming 1960's mod band (who's name escapes me at the moment) was killed this way. More recently, a preacher fellow was in a baptismal fount down in Texas. (no Tele, but a wired microphone) He had his bare foot on the metal drain plug in the baptismal, and he grabbed the microphone. Unfortunately, the heater/pump in the fount was improperly wired (inverted polarity) He was killed. Same principle.

So, I say don't sweat the death cap, make darned sure you have a polarized power plug!

[Riffraff12571]

Originally Posted by Bones

Tone is in the death cap, a lot of people don't realize that.

[TheRumRunner]

Great info there CBG and I agree wholeheartedly. I have a bunch of old amps like Magnatones and various Valco's that I have refitted with a three prong cord that ensures I keep the polarity correct. Just to be safe, I always use one of these to check the source as you never know how the "wall" is wired....



DW

[Jimmyspaz]

Keith Relf and Leslie Harvey (Alex Harvey's brother) died of faulty grounds on their amps. Of course they were both in the UK so we are talking 240 volts not 120.

[jmiles]

CBG wrote;

"Let's say you have a non-polarized power plug on your vintage Grestch 6159 amp. In a hurry at the big outdoor beerfest/concert, you get the hot and neutral reversed by inverting the plug in the stage power box (Wide is neutral, narrow is hot - but, hey! With your Grestch's non-polarized plug you can put it either way!) Unfortunately, at today's beerfest, you've put it in backwards. You're still o.k. for the moment. You fire up your amp, grab your Tele, skronk a couple chords and all seems well. But this day, it's not. You step up to the mic, stick your lips to the grounded wire mesh grille of that SM58 and your fingers to the strings of your Tele, and get ready to wail! Unfortunately, your 120vac hot wire is connected to chassis - because you flipped the plug upside down! Now remember that your Tele's strings are connected right to your amp's chassis through the shell of the 1/4" plug. Today that chassis is connected to the HOT (black wire) of your AC supply. Guess what? Your chassis on your amp is hot - relative to the "real world" ground (NEUTRAL) of the SM58, who's wiremesh grille is connected directly through "shield" to the sound system console. Congratulations, your hand is the hot - your lips are the ground - your heart is the signal path and you are dead."

Happened to me in '63! All except the last three words. I'm still here, and have gotten bigger shocks since then. Been really lucky. In '63, the mesh pattern of the mic was burnt into my lips! Hagstrom into a Ampeg RR, SM58.

[SoK66]

Back in the day I got blown of my feet when a 6" blue spark jumped from an ungrounded house mic to my lip. Same thing happened to one of my bandmates, who should have been hospitalized. Worst is if the jolt goes from one hand to another, because it crosses your chest and can stop you heart. This is serious stuff, folks, don't take it lightly.

[die Bullen]

sigh- brings back memories of my old v-4 before my pal put a grounded plug on it. It used to shock me with impunity if I'd forget to flip that polarity switch.

[Fret Wilkes]

Around 1980 or so we had "roadies" helping us lug our gear. Nice guys, but not the brightest bunch. So we are playing in this older club and the "roadie" sets up my amp for me (IVP preamp-> Furman RV-1 Reverb-> Crown D150A). Little do I know, where he plugs the amp in is an old two wire, ungrounded outlet. He breaks off the ground on the cord powering the rack and plugs it in. I walk up to sing a tune and BAM...blue spark right in the lip. I fall backwards, collect myself and say to the bass player; "Did you see that? The lights went out!". He said; "No...YOUR lights went out, nothing changed here". I then touched the tuning key to the SM58 windscreen and it exploded in sparks and put a nice burn in the chrome of the tuner. I NEVER want to have that happen EVER again. From then on I lugged and setup my own gear no matter what a drag it was.

I told that story to a talented soundman that worked with us in later years and he would always put a multimeter on the mike and guitar to show me that it was safe! I was spooked for sometime after that jolting episode.

[BritishBluesBoy]

Weird... How did that post end up here? Hmmm...