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5e3, power cord colors and fuse connection

Discussion in 'Shock Brother's DIY Amps' started by choosebronze, Jul 1, 2020.

  1. choosebronze

    choosebronze TDPRI Member Ad Free Member

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    I feel dumb asking this one, but I don't love messing around with electricity if I'm not sure. I've built a few amps that all had white/green/black power cords. I just got a 5e3 kit from Boot Hill, the parts all look great, but the power cord has green/blue/brown wires.

    On the wiring diagram, Dave wrote "BRN" where the hot black wire would typically connect (to the fuse), and "BLUE" where the white neutral wire would typically connect (wire nut to the PT). To be sure I ran continuity to the prongs. I have continuity between the brown wire and the "left" prong, and blue to the "right" as seen below. It doesn't appear either blade is larger. Safest wiring is hot to the fuse, right? Does that mean I should be connecting the blue wire to the fuse, and the brown wire to the PT primary?

    plug.jpg
     
  2. dan40

    dan40 Friend of Leo's

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    Yes. On a normal polarized plug, the neutral side will be the one with the larger prong labeled "brown". The hot side will be the narrow prong which will be the one labeled "blue" in your drawing. As long as the ground prong stays attached to your plug you will not be able to insert it incorrectly. If it were to ever break off though there will be the possibility to insert it into the outlet wrong.
     
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  3. King Fan

    King Fan Poster Extraordinaire Ad Free Member

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    ^^^ this. Wire color doesn't matter per se, but you're right, we want hot to go to fuse then to switch then to a PT primary, and neutral to the other PT primary. As Dan says, don't look for a wide prong on a 3-prong plug -- the ground prong keeps it in the correct L-R orientation. Do look for a wide *slot* on your outlet -- that's the *neutral.*

    Except... you want to make sure your hot and neutral (and ground) are wired correctly at the outlet -- surprisingly frequent issue in the US. So buy an outlet tester at the hardware store and put it to use.
     
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  4. Peegoo

    Peegoo Poster Extraordinaire

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    Look here (click on image to expand):

    [​IMG]
     
  5. rough eye

    rough eye Tele-Meister

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    right so based on this blue is white (neutral).
     
  6. choosebronze

    choosebronze TDPRI Member Ad Free Member

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    Awesome thank you guys. Seemed like I was right, but the diagram said differently, and for whatever reason I have a mental block on the home wiring. I’m fine in the chassis but as soon as I get to the wall I get confused.

    Good call. I assumed my home is wired correctly but it’s 90 years old with all kinds of weird things done to it. I should verify that.
     
  7. David Barnett

    David Barnett Doctor of Teleocity

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    Just out of curiosity - why doesn't Kirchoff's Law apply here? Why does the order of the fuse, switch, and primary matter, when they're all in series?
     
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  8. King Fan

    King Fan Poster Extraordinaire Ad Free Member

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    It isn't about the order of things when the circuit is *intact,* it's about what stays hot (or becomes hot) if a rat chews some insulation, your switch breaks, your fuse blows, etc. There are actually arguments for other arrangements -- some folks have said switch before fuse (in case you might get shocked by a live fuse holder) but the general drift is you want the amp to go cold beyond the fuse if it does blow, and beyond the switch if that fails, etc. Switching the neutral is a common mistake that in fact works fine... as long as nothing goes wrong.

    It's like making your ground wire longer than black and white in case the amp falls off the stage and hangs by its power cord tearing the wires off their anchors one at a time. It's all theoretical until something goes wrong. It's like a bleeder resistor (or the fuse itself, or all the safety grounds in your house) -- it doesn't matter if nothing fails and you don't make any mistakes.
     
  9. Ten Over

    Ten Over Tele-Holic

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    Which one? They always apply, that's why they're called laws. They still apply as your amp burns and catches your house on fire.
     
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  10. choosebronze

    choosebronze TDPRI Member Ad Free Member

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    Wait this post threw me for a loop. Pretty sure that image confirms the opposite.
     
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  11. tubegeek

    tubegeek Friend of Leo's

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    Because Oscar or David could complete the current loop instead of the primary if all goes according to The Bad Plan. Kirchoff's situation really only applies to The Good Plan and The Intended Connections.
     
    Last edited: Jul 2, 2020
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  12. Paul-T

    Paul-T Tele-Holic

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    Just a note as i"m confused. Standard Euro wiring is that brown is hot (live) and blue is neutral. Is this really the opposite way around? I would always connect brown to fuse and then switch.

    IN europe we tend to switch both live and neutral for safety, fwiw.

    In europe the convention is that blue is 'more' neutral, and will be at earth (ground) potential back at the local step-down transformer. However, there might still be a potential difference between neutral and ground in one's house so neutral can still give you a shock (or fire risk).
     
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  13. Peegoo

    Peegoo Poster Extraordinaire

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    Yes, brown is live and blue is neutral.

    In the UK and in some places in Europe homes are wired unlike those in the US.

    Instead of branches like a tree containing live, neutral, and ground running from the power distribution/circuit breaker panel in the US, UK homes are wired in rings or loops ("ring mains" scheme); each with a usually 30-amp breaker. If you've never messed with this kind of system, it is puzzling at first.

    I think this system was standardized around WWII due to copper shortages and the need to reduce the amount of wiring in homes. If I'm wrong about that, please set me straight!

    [​IMG]
     
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  14. tubegeek

    tubegeek Friend of Leo's

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    Interesting! Thanks for that tidbit.
     
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  15. Peegoo

    Peegoo Poster Extraordinaire

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    Get yourself one of these:

    [​IMG]

    They cost less than $10 and they are the cheapest life insurance you can buy. They tell you immediately if an outlet is correctly or incorrectly wired. When you have two yellow lights, it's correct. Anything else is a potentially deadly hazard.

    Test every outlet in your house--and this means test both outlets of a pair on the same plate. This is important because sometimes a dual receptacle is split; one could be correct and the other may be wrong.
     
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  16. tubegeek

    tubegeek Friend of Leo's

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    Man, Joe Handyman really has to WORK to pull that one off though. "Wall switch in the neutral? Sure!"
     
  17. King Fan

    King Fan Poster Extraordinaire Ad Free Member

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    Forget the image and wire color and what Dave drew for connections and which color we say. Use your continuity tester while you look at a duplex outlet in the wall. In the US, the left slot when looking at the wall should be neutral, so the right prong *when looking at the plug* is neutral. Rob of course has it right...

    [​IMG]
     
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  18. Peegoo

    Peegoo Poster Extraordinaire

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    I've seen it. The first time I got bitten by it before I saw it tho :confused: That's why I am a safety freak about this stuff.
     
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  19. Peegoo

    Peegoo Poster Extraordinaire

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    It's the same problem as "stage right" and "audience right."

    They's opposites!
     
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  20. rough eye

    rough eye Tele-Meister

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    when i was an electrician i wired a few houses, and never did one or saw one done in a loop.

    edit: oh i see, done primarily in the UK. I'm in the US.
     
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