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Gots a question about my power cord

Discussion in 'Shock Brother's DIY Amps' started by dhodgeh, Sep 15, 2020.

  1. dhodgeh

    dhodgeh TDPRI Member

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    The insulation on my homebrew 5F1 power cord has separated from the plug itself:

    [​IMG]

    So. should I do the right thing and replace the entire cord, or the easy thing and just replace the plug?

    TIA

    D
     
  2. wabashslim

    wabashslim Tele-Afflicted

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    Duct tape.
     
  3. sds1

    sds1 Tele-Afflicted

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    No shame in just replacing the plug.
     
  4. wabashslim

    wabashslim Tele-Afflicted

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    Are you implying there's shame in duct tape?
     
  5. Pick_n_Strum

    Pick_n_Strum Tele-Meister

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    If it were me, I don't think I'd have even noticed that. But if I did, I probably would replace it for 2 reasons:

    1. I like doing that kind of stuff
    2. I've got a 15 month old running around my house and getting into things. In general we keep a close eye on him but you never know.

    If neither of those were true, I'd probably put electrical tape on it for the interim and then replace when I felt like it.
     
  6. Ronkirn

    Ronkirn Doctor of Teleocity

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    that's the classic Asian cheepo wire.. they cannot even go with black white, and green so ya know what's what... looks about like 18 AWG too which is too light. get ya a good cord, at least 14 AWG and replace the whole thing.

    r
     
  7. gregulator450

    gregulator450 Tele-Afflicted Silver Supporter

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    you can get a 14awg power cord on Amazon for less than $20.
     
  8. schmee

    schmee Doctor of Teleocity Silver Supporter

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    I never seem to find good plugs. They are cheap, thin metal parts in side, big and boxy etc. I would just do the cord personally. A plug will work though. But a new good cord is likely... $6? a Decent plug $3-4?
    Some cords are better than others. Some are really stiff and ungainly. Some nice and flexible. Dont get sent astray looking for a big wire gauge cord either. you dont need a heavy cord, especially for that amp!
     
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  9. Ronkirn

    Ronkirn Doctor of Teleocity

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    If ya buy one off the internet, be certain to get one that's "standard" with black, white, and green internal wires.. that way you know what to hook to what.. Black = Hot, White = Neutral, and Green is Earth, Ground, whatever ya call it where ya are..

    r
     
  10. esseff

    esseff Tele-Afflicted

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    I once moved an office desk away from the wall to clean the carpet and suddenly there were sparks coming from the printer lead at the plug. The cable had been bent at 90 degrees against the wall and the insulation on the apparently sturdy sheath and conducting wires had cracked and shorted when they were straightened. So much for fuses...
    Modern plugs are bonded to cables and if any of mine get damaged I just cut the plug off and fit a new one with screwed-on cable connections.
     
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  11. esseff

    esseff Tele-Afflicted

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    In the UK, mains power cables are coloured Brown for live, Blue for neutral and Yellow with Green stripes for ground.
    An easy way to remember where they go on the plug is to take the second letter of each solid colour thus:
    Brown - second letter = R. R = Right.
    Blue - second letter = L. L = Left.
    The ground obviously then goes to the remaining centre pin.
     
  12. Nickfl

    Nickfl Friend of Leo's

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    So he needs "at least" power cord that can handle 15 amps for an amp with a 1 amp mains fuse?

    Seems like 18 AWG should be fine since its still rated at 7x the amps fuse rating. Also has the advantage of actually fitting in the strain relief cutout in the chassis, unlike a much thicker 14 ga cord...
     
  13. Ronkirn

    Ronkirn Doctor of Teleocity

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    1 amp?? what??? you mean we're not supposed to wrap a blown fuse with tin foil like we did in the 60's? :eek:

    r
     
  14. andrewRneumann

    andrewRneumann Tele-Holic

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    The explanation starts at 3:25!

     
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  15. Boreas

    Boreas Tele-Afflicted Silver Supporter

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    Up to you. Any good plug you buy will likely last longer than the amp will. But if you have ever wished for a longer cord, now is the time to do it!
     
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  16. Blrfl

    Blrfl Tele-Holic

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    That isn't how it works. Fuses and breakers protect what's downstream, so the one in the amp isn't a mains fuse, it's an amp fuse sized to blow before the wiring inside is damaged.

    The line cord is upstream from the fuse in the amp, which means it has to be able to carry everything any wall socket it's plugged into can dish out. In the U.S., that's going to be 20A. (Most household outlets are 15A, but the plug for those is compatible with 20A sockets.) If the cord isn't big enough to carry the full 20A and is damaged in a way that allows more current than it can handle but not enough to trip the breaker upstream, there's a fire risk.
     
    Last edited: Sep 17, 2020
  17. Nickfl

    Nickfl Friend of Leo's

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    [/QUOTE][/QUOTE]

    No, that's exactly how it works... the fuse in the amp is on the primary side of the power transformer in line with the electrical mains wiring, it is there to protect your house not your amp. That one amp fuse is sized the way it is because if the amplifier enters a condition where it is drawing more than one amp something is very wrong and it has potential to cause a fire in the wiring inside the amp or its power cord, that fuse will open if the current exceeds one amp and the electricity in the main circuit will stop flowing. That means that the current in the amplifiers power cord plugged into the wall will never under any circumstances exceed one amp unless someone does something really stupid like wrap the fuse in tin foil as @Ronkirn alluded to.

    Consider this, if everything plugged into a standard house electrical outlet needed to be rated for the current carrying capacity of the breaker and the wiring in the wall why do appliance power cords and lamp cords etc in gages smaller than 12 even exist? If what you were suggesting was actually the way it worked those power cords would not be allowable on any UL listed or CE certified appliances and yet there they are for all the world to see...
     
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  18. rangercaster

    rangercaster Poster Extraordinaire

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    Sometimes, a good jolt of 110/120 volts reminds me I need to be more careful with my gear maintenance...

    .
     
  19. Squawker

    Squawker Tele-Meister

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    Nothing wrong with the colours. Just depends where it's produced in the world. UK/Europe would have Brown = Live, Blue = Neutral, Green/Yellow stripe = Earth. But most European wiring systems don't actually differentiate live and neutral in any meaningful way (UK does, since there's a fuse in the plug on the live side). Just pointing out that things vary around this big old globe but are just as correct.
     
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  20. Blrfl

    Blrfl Tele-Holic

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    If you're trying to imply that the fuse in the amp protects anything upstream of it, that's flat wrong.

    Here's the power supply section of a Fender 5F1 Champ marked with a couple of spots where a short might happen (assume the switch is closed):

    5f1.png

    A short at A means current flows from one side of the plug, down that side of the cord, across the switch, across the short, through the fuse and back up the other side of the cord to the other side of the plug. The fuse, being part of that circuit, will blow once the current exceeds its limit. This is what you described.

    A short at B means current flows from one side of the plug, down that side of the cord, through the short, back up the other side of the cord and to the other side of the plug. Nowhere in that scenario is the amp's fuse in the path of the current flow.

    Yup, so they are. There's something you overlooked. Since you brought up UL, let's look at it from that angle:

    The National Electrical Code defers to UL standards for the circuit breaker, the panel where it's mounted, the wiring in the house and the outlet on the wall. The standard governing circuit breakers specifies a trip time that decreases as the multiple of the rated load increases. Those requirements came from more than a century of studying how long various kinds of wire with various kinds of insulation can withstand carrying more current than they're supposed to before they become a fire hazard. There's also a UL standard (817; I don't have a copy so I can't cite anything in it) for cord sets on appliances, but I'd bet good money it takes that into account.

    If you buy an amp that is UL-approved and plug it into an outlet fed by a circuit that meets the NEC all the way back to the breaker, it means the cord subjected to a full or partial short will not become a fire hazard before the breaker trips. UL's figured this stuff out and they're generally regarded as knowing what they're doing. I know people who've put products through UL approval, and they're nothing if not thorough.

    TL;DR: Cords don't have to carry the full current forever, just long enough for the breaker upstream to trip.
     
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