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Twin Fuse Power Cord

Discussion in 'CB and Export Equipment and Accessories' started by wildchild455, Feb 9, 2019.

  1. wildchild455

    wildchild455 Member

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    I got myself a "Workman CB 3 AXX power cord for my RCI 2950 it came with a 10 amp fuse on the positive and a 4 amp fuse on the negative. I know the 10 amp fuse is too big for the radio. My question is what amp fuse should I use in the negative and the positive( Not sure of the amp rating on the from the old broken cord no markings on that fuse). Thanks


     

  2. Cutlass327

    Cutlass327 Active Member

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    I have one of those too, which I never understood the 2 values, as power in = power out, so if a 4A ground fuse (with isolated chassis mount) is going to blow, the 10A will never blow. I'd figure that both would have to be equal.

    Maybe someone here can enlighten us both?
     
    Eldorado828 likes this.
  3. Eldorado828

    Eldorado828 From the high plains of Texas

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    The 10 amp fuse should be fine for the 2950 being a dual final rig.
     
    psycho likes this.
  4. 338_MtRushmore

    338_MtRushmore Sr. Member

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    If your radio is tweaked and peaked you need more current on the negative lead. Ghost watts come from the dark side, that's why we call them "ghost watts".

    Sorry, that's all I got (n)
     
    midnight special likes this.
  5. Captain Kilowatt

    Captain Kilowatt Professional Amateur
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    Both fuses should be the same and IIRC that radio comes with a 7 amp fuse in the power lead. A 4 amp is a bit too light for it. There is a long debate over using a dual fused power lead. It won't hurt if you install a fuse on the negative lead, and the wiring harness that ships with most Amateur mobiles has two fuses.
    The fuse on the negative (ground) lead is only really required on installations that connect directly to the vehicle battery.
    The reason for the fuse, is that if the vehicle grounding from the battery to the car frame/engine should fail, either partially or completely, the radios negative lead "ground", in some cases, will become the return path to the battery for the vehicle, causing the wire to burn.
    This is not an issue for radios connected to power supplied, the vehicle chassis, or batteries not in a vehicle.
    ALWAYS FUSE THE POSITIVE LEAD!
     
    drgrant, binrat, Cutlass327 and 2 others like this.
  6. wildchild455

    wildchild455 Member

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    Maybe this will help more it does 10 watts high power and 2.8 watts on low power on AM and FM on SSB it does 13 watts on low power and 37 watts on high power. I found the power cord at a pilot truck stop while I was on my way home from a doctors visit that was the only kind they had was the 2 fuse ones (I would have rather had the single fuse type but if thats all they had at the time)
     
  7. Cutlass327

    Cutlass327 Active Member

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    I hadn't thought of an issue with losing the body ground - Like on a Detroit when the engine ground breaks, the power steering line being wire braided becomes the engine ground for cranking that engine......
     
    Shadetree Mechanic and Slowmover like this.
  8. SIX-SHOOTER

    SIX-SHOOTER Well-Known Member

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    I was told that the fuses on the ground side was started due to power surges coming in on the ground side & that a smaller amperage fuse was used so it would blow quickly if this happens but I have never tested it so it's only something I heard somewhere over the years? Sounds good but I am NOT a tech though I have stayed at least once in a Holiday Inn Express. :po_O

    SIX-SHOOTER
     
    Cutlass327 likes this.
  9. Slowmover

    Slowmover Well-Known Member

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    POWERWERX for custom cable assemblies. Spec each lead differently. (Yeah, I’ve made plenty of my own. So what? PW does nice work).

    Since I’ve seen the argument go both ways, I just fuse them both the same.

    A better question is what does YAESU or MOTOROLA , etc, advise with installation of their equipment? (A discussion over on eLightbars where public service installers debating same).
     
  10. Captain Kilowatt

    Captain Kilowatt Professional Amateur
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    But current drawn in the pos lead equals curren tdrawn in the neg lead so if the radio required a 20 amp fuse it would require BOTH leads to have a 20 amp fuse. If a 5 amp was placed in the neg lead and a 20 in the pos lead the 5 amp would blow under normal use......or rather attempted use.
     
    drgrant likes this.
  11. drgrant

    drgrant Member

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    I always usually end up going bigger than stock on a radio but not by extreme amounts. They should both be the same, regardless.

    The whole purpose of the fuses is not so much to protect the radio as it is to keep your car or house from catching on fire.
     
    Chevboy0167 likes this.
  12. Cutlass327

    Cutlass327 Active Member

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    The only thing I can think that would make a difference in the P-in=P-out argument is that the chassis is a ground point usually too, so maybe they expect some of the power to go thru that way? Or, is it where P-out and Ant-out = P-in?

    P-out (power out)
    P-in (Power in)
    Ant-out (Antenna output)
     
  13. sunbulls

    sunbulls Well-Known Member

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    I was thinking the same thing, except the negative wire on most CB’s is not connected directly to the radio’s chassis, only through bypass capacitors. Therefore both negative and positives leads draw equal amperage regardless of any possible external ground fault condition. This enables these same radios to be used on a positive ground chassis that is found on some Mack’s.
     
    Cutlass327 likes this.
  14. sp5it

    sp5it Master of puppets

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    Short, negative cable to chassis of car, positive cable with fuse to battery +.
    Mike
     
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  15. Captain Kilowatt

    Captain Kilowatt Professional Amateur
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    All my Yaesu equipment came with a dual fused power cord and recommended direct connection to the battery for BOTH leads.
     
    Slowmover likes this.

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