Wondering about 3 prong VS 2

Discussion in 'Amp Central Station' started by Allenjason95, Apr 2, 2020.

  1. Allenjason95

    Allenjason95 TDPRI Member

    Age:
    98
    Posts:
    5
    Joined:
    Apr 2, 2020
    Location:
    Sweetlips Tenn
    Hi, I have a late 60’s Deluxe Reverb in great condition that belonged to my grandfather.

    I was checking out old Deluxe and old amps in general and everyone seems to advise putting a 3 prong cord on to replace the two prong.

    Would. 3 prong adapter serve the same function in making it safer?

    thanks.
     
  2. Peegoo

    Peegoo Friend of Leo's

    Age:
    60
    Posts:
    2,266
    Joined:
    Oct 11, 2019
    Location:
    USA
    No, not at all, because an original two-conductor cord is not polarized. Even with a three-prong adapter, the amp's metal chassis could still be live at mains voltage. If you look at a modern two-wire power cable, you'll see one of the plug blades is narrow and one is wide. The narrow blade fits into the corresponding narrow slot in a modern outlet, that is the hot side. The wide blade fits into the the wide slot, and that is the neutral side. Because a modern plug like this is polarized, it fits the outlet only one way and preserves polarization. But neutral and ground are not the same, even though they may be at identical potential at your breaker panel. You need that third ground wire to make your amp safe to use.

    Older two-wire plugs are not polarized like this, and they can be flipped to fit an outlet either way. This is why they are dangerous, because if the ground reverse switch is in the wrong position, you will get zapped.

    *Properly* converting a two-wire mains cord to the grounded three-wire version is probably the cheapest life insurance you can buy. When you have the conversion done, disconnect the 'death cap' and the ground reverse switch. They are additional liabilities and can still lead to a bad shock...or worse.

    Click the image to enlarge:

    [​IMG]
     
    Last edited: Apr 2, 2020
  3. Allenjason95

    Allenjason95 TDPRI Member

    Age:
    98
    Posts:
    5
    Joined:
    Apr 2, 2020
    Location:
    Sweetlips Tenn

    Thanks, I've gotten shocked by it before, no fun. I know nothing about amps and very little about electricity. I'm going to take it to a shop and have it gone over sometime soon so I'll have that done while it's in. Thanks!
     
  4. televillian

    televillian Tele-Afflicted

    Posts:
    1,091
    Joined:
    Oct 3, 2013
    Location:
    Clarkdale, AZ
    don`t assume that wall outlet is wired correctly
     
  5. Paul G.

    Paul G. Friend of Leo's

    Posts:
    3,036
    Joined:
    Mar 17, 2003
    Location:
    Rhode Island
    1. The 2-prong not being polarized, and the possibility to put AC on the chassis - to which your are connected. 2. You know you're in phase with other properly grounded equipment, so you don't get bit if you touch something connected to another amp, say a microphone, 3. When you have a 3-prong cord, your chassis is directly connected to earth. Black wire is the hot, white wire is the return and the green wire is a direct, low resistance path directly to earth. This is a safety feature. Should there be a short in the amplifier, say in a transformer, or a capacitor that leaks DC to ground, the lowest resistance path for any voltage is that green wire, not your body. I know the fuse should blow, but before it does you can get zapped, and there are situations where the fuse might not blow, at least not right away, and you don't want to become part of the circuit.

    I won't operate an amp that does not have a properly installed 3-wire power cord and the "death cap" and ground or polarity switch disconnected.
     
    awasson likes this.
  6. Peegoo

    Peegoo Friend of Leo's

    Age:
    60
    Posts:
    2,266
    Joined:
    Oct 11, 2019
    Location:
    USA
    "don`t assume the wall outlet is wired correctly"

    If it's not, the third (ground) wire is what will help prevent you getting shocked.
     
    Andy B, nojazzhere and awasson like this.
  7. Peegoo

    Peegoo Friend of Leo's

    Age:
    60
    Posts:
    2,266
    Joined:
    Oct 11, 2019
    Location:
    USA
    Allenjason95, when you take the amp in to get the work done, make sure to specify the wiring in the diagram above.

    I've seen more than a few rewires done by "competent techs" that send the black mains wire to the power switch first, and then to the fuse. That is wrong because it defeats an additional level of safety.

    Black wire to the fuse, then to the power switch.

    Some techs will say attaching the new ground wire using a transformer mounting screw is risky because the screw can vibrate loose; they prefer to solder it directly to the chassis. That works too. However, I've never had one come loose because I use a thread locker on the nut.
     
    Andy B and awasson like this.
  8. Paul G.

    Paul G. Friend of Leo's

    Posts:
    3,036
    Joined:
    Mar 17, 2003
    Location:
    Rhode Island
    This is how I do it too! If the fuse does blow, there will be no AC anywhere in the amp.

    If there's a good spot nearby, I will solder the wire, but I don't have an issue with putting a lug on the wire and attaching it to a transformer screw. I do leave this wire a bit long and make a loop in it so that if somehow the cord gets yanked hard, there is some slack to prevent disconnecting the ground.
     
    tubegeek likes this.
  9. archetype

    archetype Fiend of Leo's

    Posts:
    4,063
    Joined:
    Jun 4, 2005
    Location:
    Williamsville NY
    Right! A $10 AC receptacle polarity tester should be in everyone's kit for home and especially when gigging.
     
  10. Jabberwocky

    Jabberwocky TDPRI Member

    Posts:
    6
    Joined:
    Oct 21, 2018
    Location:
    'Tis safer under a bridge...
    I came to congratulate you on getting your grandpa's Deluxe Reverb. Treat it right. Treat it well. Grandpa left you a very nice gift should you decide to part with it one day.

    While you are at the tech, check to see if any old caps are leaky and replace those. Go to a tech who is into proper restoration and will use the proper correct parts. You want to maintain or enhance the value of your Deluxe Reverb, not depreciate it.
     
  11. KCJonez

    KCJonez Tele-Holic

    Posts:
    642
    Joined:
    Feb 3, 2011
    Location:
    Toronto
    I don't know anything about this, but just out of curiosity...if all these amps were all originally 2 prong, back in the good old days, was everyone who played guitar getting electrocuted?? We've all read about the overdoses and helicopter/motorcycle crashes...haven't heard much about all those rockers who lived hard but died young at the hands of the 2-prong outlet.
     
  12. nojazzhere

    nojazzhere Doctor of Teleocity

    Age:
    68
    Posts:
    11,373
    Joined:
    Feb 3, 2017
    Location:
    Foat Wuth, Texas
    I haven't seen anyone mention.....if you change to a three prong cord, flipping the "polarity" switch on the back will effectively defeat the three-prong's purpose. You'll still have the third wire ground, but your chassis may still be "energized". Remove the polarity reverse switch when you change the cord.
     
  13. Paul G.

    Paul G. Friend of Leo's

    Posts:
    3,036
    Joined:
    Mar 17, 2003
    Location:
    Rhode Island
    A few did die, I'm sure their friends and family did not take it lightly. Even if you don't die, the experience of getting shocked is extremely unpleasant. Extremely. I wish I wasn't speaking from experience. I remember one time touching my lips to a mic, it felt like my head was in a vise, my eyes pulled deep in their sockets and I saw stars. It was an outdoor festival and nobody was paying attention to polarity. I was in the opening act, so, lucky me.

    AC will kick you back and you'll probably survive. Probably. DC will cause your muscles to contract and you don't let go until you're in another plane of existence.
     
  14. schmee

    schmee Doctor of Teleocity Silver Supporter

    Posts:
    10,376
    Joined:
    Jun 2, 2003
    Location:
    northwest
    1950-1990 "Rock on!"
    1990 to 2020 "I won't play one of those until it has a 3 prong cord"
    :eek::lol:
    I think the two vs three prong is a bit over emphasized sometimes, after all, we played those amps for 30 -40 years and survived. But yes, it can be dangerous. Besides, the 3 prong will get rid of some hum for you and allow you not to get your lip zapped!
     
  15. Paul G.

    Paul G. Friend of Leo's

    Posts:
    3,036
    Joined:
    Mar 17, 2003
    Location:
    Rhode Island
    "Tragedy is when I cut my finger. Comedy is when you fall into an open sewer and die. " -- Mel Brooks
     
    BobbyZ likes this.
  16. BobbyZ

    BobbyZ Doctor of Teleocity

    Posts:
    12,534
    Joined:
    Jan 12, 2011
    Location:
    Snellman MN
    I grew up on two prong amps. New amps then had grounded cords but new amps were expensive.
    You can play a two pronger without getting shocked if you're not a dumbass, trouble is the world is crawling with dumbasses these days. They have to put stickers on chainsaws that say, "DO NOT STOP CHAIN WITH HAND".
    That's the level of stupidity we have to deal with today. For that reason if I work on an old amp it gets a grounded cord.
     
    LuthRavin, Andy B and screefer like this.
  17. Paul G.

    Paul G. Friend of Leo's

    Posts:
    3,036
    Joined:
    Mar 17, 2003
    Location:
    Rhode Island
    And we didn't need dang seat belts. And if bad pork killt ya, well we were glad to have it. And it was 3 miles, uphill both ways. You call this snow, why we had snow up to yer eyeballs, but we couldn't see 'cause eyeglasses was fer sissies and momma used ta whack us with a pall peen, but we still danced on Saturday, despite the rickets but it didn't matter 'cause Polio'd get ya anyway...wait! What was I talkin' about? Oh yes, I had an onion on my belt, which was the style at the time. It was a yellow onion, you couldn't get the white ones on account of the war...
     
    Last edited: Apr 5, 2020
    stevemc, Tele-phone man and BobbyZ like this.
  18. edvard

    edvard Tele-Afflicted

    Posts:
    1,514
    Joined:
    May 15, 2016
    Location:
    Bremerton, WA
    The only way that a 3-prong adapter MIGHT help is if you figured out which way to plug your amp into it so the polarity is always 'right' (because you can't plug a 3-prong in 'wrong'), but because you can't guarantee that any given outlet in any house or venue will be wired correctly 100% of the time, not even that is a sure thing. Plus, because the chassis will still be essentially 'un-grounded' it won't save you from failure of the Death Cap or other things already mentioned. Replacing the original cord with a 3-prong wired correctly is the best and easiest way to protect yourself from accidental electrocution via your gramp's old amplifier.

    I have a 1952 Deluxe 5A3 that belonged to my grandfather. The last time it "tickled" me was the last time. I put a 3-prong on it and never looked back. I'll never sell it, so I'd like to be around for a few more years to appreciate it and remember him when I play it. If you're concerned about the resale value, keep the cord and any other bits tucked away in the back of the amp.

    Near-death: Keith Richards, George Harrison, Ace Frehley, et al.
    Actual death: Les Harvey from Stone the Crow, Keith Relf from the YardBirds, John Rostill from The Shadows. Les died on stage, the other two died at home studios. There was a rumor going around that Keith died from playing electric guitar in the bathtub, but that's not true.

    Also, this thread: https://www.tdpri.com/threads/guitarists-who-were-electrocuted-while-playing.162036/
     
    DrPepper and BobbyZ like this.
  19. DrPepper

    DrPepper Friend of Leo's Ad Free Member

    Age:
    61
    Posts:
    3,075
    Joined:
    Nov 24, 2017
    Location:
    Texas
    An outlet tester is less than $10, everybody should have one in their gig bag (and use it religiously)...
     
    BobbyZ and Paul G. like this.
IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.


  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.