The "Death Cap" Thread...

[emtjr928]

The '73 twin I'm working on has a factory installed three prong cord, a groung switch and what looks like a "death cap" from the center lug of the grnd switch to chassis. I plan to take the grnd switch out of the circuit just to be safe.

[SoK66]

You don't really have to remove that cap. Your '73 Twin should have a 3 way ground switch. Leave it in the center position and it's as if the switch and cap aren't there. The other two positions were intended to be used like the old two-position switch, in cases where the outlets had not been upgraded to three-prong. This was quite common back in the day and you were supposed to use a three to two adapter. Some guys would just clip off the ground prong, which is why you'll see so many amps from that area with replaced plugs or new cords.

[Bolide]

[QUOTE=stingray_65;2479653there are so many bars that are wired by a patron.

[/QUOTE]

Too right!

Used to work at a bar, and got bit regularly by miswired outlets, and watched as the owners had a patron whose only qualification was watching Bob Vila on the Discovery Channel do more bad wiring work (fun is watching two clowns fish Romex through hard conduit).

But, even people who should know better....
During an INSURV inspection every 110 outlet in one workspace of a new construction Trident sub were found to be wired backwards; This work was performed and inspected by licensed electricians.

Moral: Use only qualified people to do the work, then double check to make sure they did it right.

[donh]

Originally Posted by SoK66

You don't really have to remove that cap. Your '73 Twin should have a 3 way ground switch. Leave it in the center position and it's as if the switch and cap aren't there. The other two positions were intended to be used like the old two-position switch, in cases where the outlets had not been upgraded to three-prong. This was quite common back in the day and you were supposed to use a three to two adapter. Some guys would just clip off the ground prong, which is why you'll see so many amps from that area with replaced plugs or new cords.

At the very least I'd clip the cap's lead from the switch and the end of the cap, just in case.

I also do this: http://audiosys.com/safety-circuit.html
I've been knocked down by this kinda thing exactly twice too often, and I'm not going for three!

[BobbyZ]

Maybe I should upgrade my Deluxe to a 3 prong plug. I've just learned not to touch another amp while touching my guitar. I learned this by getting the crap shocked outt'a myself !
I should'a done this when I recapped it. Just didn't have a cord handy.

[SoK66]

FWIW, Ace Hardware sells a grey, three-prong cord in 9' lengths that works great on vintage tweeds and browns. The right color and virtually the identical diameter.

[Wally]

Thanks for the tip on that one, Sok66.

[Timbertea]

Originally Posted by Wally

EAsyEB, as good as you think that Supro is, with a grounded cord (safer and less noise) plus a fresh set of electrolytic capacitors, that amp will sound like it hasn't in..what?..probably 30 years.

I've never understood the great reluctance of people to upgrade filtering capacitors, and properly ground an amp to make it electrically safe. Less noise, more punch, more power, more gain, no voltage grounding through the heart.

[Wally]

Originally Posted by Timbertea

I've never understood the great reluctance of people to upgrade filtering capacitors, and properly ground an amp to make it electrically safe. Less noise, more punch, more power, more gain, no voltage grounding through the heart.

+1...and...more sparkle(high end definition), more dimensionality---hard to explain but easy to hear. When e-caps are weak, there are some incorrect harmonics being created. With fresh caps and correct harmonics, there comes a 3-d dimensionality and liveliness to the sonics. ONce one hears the difference between old and fresh e-caps, one will never be reluctant to change old electrolytics, ime.
Now, if I were to purchase something that was NIB from the '50 or '60's, then I might consider that such an amp should never be worked on....and never turned on, either. Museum piece for a serious collector...big bucks in such a casem andone would not want to change anything. I once had a booth nect to a fellow who has a world class Fender amp collection. HE walked up with a perfectly pristin Fender amp box...inside of which was a NOS/NIB 5F1 Champ. HE reluctantly pulled the amp out far enough to show me that the amp was indeed NEW IN THE BOX.
IF an old is going to be played, it shoud be put in proper working order, imho and ime. There are those who disagree, and they are busy burning down vitnage amps...thinking that tha lifeless, out-of-tune sound is how it sounded when it was new simply because everything is original.

[fly135]

Glad I saw this thread. My 67 Gibson Hawk has a death cap. I didn't know what the death cap was and I was scratching my head previously wondering why it was even in the circuit. It's getting snipped right away. However I already have installed a 3 wire plug, so if the cap failed it would have just blown the fuse.

[Timbertea]

Originally Posted by Wally

+1...and...more sparkle(high end definition), more dimensionality---hard to explain but easy to hear. When e-caps are weak, there are some incorrect harmonics being created. With fresh caps and correct harmonics, there comes a 3-d dimensionality and liveliness to the sonics. ONce one hears the difference between old and fresh e-caps, one will never be reluctant to change old electrolytics, ime.
Now, if I were to purchase something that was NIB from the '50 or '60's, then I might consider that such an amp should never be worked on....and never turned on, either. Museum piece for a serious collector...big bucks in such a casem andone would not want to change anything. I once had a booth nect to a fellow who has a world class Fender amp collection. HE walked up with a perfectly pristin Fender amp box...inside of which was a NOS/NIB 5F1 Champ. HE reluctantly pulled the amp out far enough to show me that the amp was indeed NEW IN THE BOX.
IF an old is going to be played, it shoud be put in proper working order, imho and ime. There are those who disagree, and they are busy burning down vitnage amps...thinking that tha lifeless, out-of-tune sound is how it sounded when it was new simply because everything is original.

I haven't come across any closest classics in my time. I've had some good luck with studios closing, for one owner, well maintained, could pass for new, but those amps were always in use until the day I bought it. I figure the amp that gets played the heck out of for 30-40 years will keep on working, and getting played the heck out of. Otherwise I see an amp that looks too new, I get leery, and wonder if its a dud.

I had forgotten all about the odd harmonic overtones, and ghost noting. I've heard those firing up a few amps that the electrolytics were way past their prime. I've only really heard that kind of off sounding in addition to played note on little SE class A amps, but I would imagine the effect is still there on push-pull designs too. I think the concert amps get a little better treatment in the maintenance department in general though. People have a harder time parting with the bucks to maintain a practice size amp than they do a concert amp.


I've wondering if there is something inherent in the designs of SE amps that makes them more vulnerable to that effect, or if its due to them generally being a lot less powerful, and makers skimping a bit on the ratings for power filtering capacitors to begin with because so many were intended for practice amps, and it just becoming incredibly pronounced as they slip out of tolerance.

[Wally]

Timbertea, some hold that all true single-ended amps have the problem you are mentioning about harmonics and ghost notes. I recap 'em and turn 'em up...love 'em.

[limbe]

I´m real glad that I am a member of a forum where the members have the right attitude about death caps and grounding.I once wrote a post in another forum where most of the members more or less were of the opinion that removing the death cap and grounding an amplifier were a thing that only sissies did.Needless to say I am no longer a member of that forum.

[phillip lee]

Watch George Harrison in Let It Be. When his lips come close to the microphone he gets a shock, then gets another one. The Techs can't figure it out.
I put what amounts to a ground loop/circuit breaker in a J-160e wiring harness on a project. The only problem as I understand it is it will only protect you one time.

[InyoTim]

I have a few old amps that I haven't converted yet. These have the type plug that will easily go in either way. I marked the correct polarity with a red sharpie. That prong goes in the small hole in the receptacle. I live in an old house with the old two hole receptacles anyway.

[jbmando]

Originally Posted by SoK66

FWIW, Ace Hardware sells a grey, three-prong cord in 9' lengths that works great on vintage tweeds and browns. The right color and virtually the identical diameter.

Is this it?

[Bill Ashton]

...and ran down to my local Ace...

Turns out it is a 16/3 cord, designed for power tools, appliances and the like. The only #18 wire they carry is 18/2, even in bulk.

Diameter looks way too big to me (I did buy one) this really fits into the chassis w/o trouble?

[Tricone]

Found this the other day regarding the installation of a 3-Prong power cord on a vintage Fender amp.

http://www.theguitarfiles.com/guitarfile644.html

[SoK66]

Originally Posted by jbmando

Is this it?

That's it. The wire gauge is a bit heavier than stock but they work fine. The outside diameter is just a tiny bit larger. Helps if you have a strain relief tool but you can use some vise grips.

[Tricone]

Originally Posted by stingray_65

My son has 2 small amps that are still wired with a 2 prong plug and no power transformer (series heated tubes)

we used a multimeter to trace which prong on the cord is neutral (wired to chassis) and colored it with a sharpie.

the neutral is the big slot on a modern receptacle.


you then plug in with careful attention .

while this is by no means the safest way and does not replace a properly installed 3 prong plug, but it does offer one more level of safety that otherwise isn't there.

https://www.hardwareworld.com/Ground...r-pKZR1O2.aspx

How do you go about measuring the prongs with a multimeter (or does this work only if the particular amp lacks a power transformer)?