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RE: [BCD396XT] Re: Fried It I think

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  • Michael Hopkins
    I agree ---- One thing I didn t mention is the use of fuses in both positive and negative wires to the battery. That also works to prevent problems. I run both
    Message 1 of 12 , Oct 9, 2012
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      I agree ---- One thing I didn't mention is the use of fuses in both positive
      and negative wires to the battery. That also works to prevent problems. I
      run both wires to the battery for a 100 watt transceiver so I don't have
      high ground currents from the transceiver running all around the car ---
      reduces the chances of noise problems from ignition as well and the
      likelihood of transients from other electronics and electrical systems
      getting to my radio. Power for my XT comes from a cigarette lighter type
      power connector. All seems to work well..











      Mike Hopkins - K1VLB

      Home: 603 882 2030

      Cell: 603 765 3736

      Mhopkins735@...



      From: BCD396XT@yahoogroups.com [mailto:BCD396XT@yahoogroups.com] On Behalf
      Of MCH
      Sent: Tuesday, October 09, 2012 4:57 PM
      To: BCD396XT@yahoogroups.com
      Subject: Re: [BCD396XT] Re: Fried It I think





      In this case, the ground wire was run directly to the battery (hence the
      original comment to not run the ground wire to the battery), and the
      chassis of the radio was grounded (likely for RF suppression reasons).

      Granted, there are cases where there would not be the complete path, but
      it's far better to just ground anything to the chassis rather than the
      battery.

      Of course, you could also insulate all the other grounds, but it's much
      easier to simply not run the ground wire to the battery.

      And yes, the chassis connection could be via the radio mount (where the
      case of the radio is grounded internally), via the antenna, via a
      speaker, or even via a GPS that is powered from the vehicle. Grounds are
      a good thing to have - just not right to the battery for that one reason.

      It's also true that the path won't last forever under a starter load,
      but by the time the path "fuses", the damage will have been done. The
      same can even be said for adding a fuse to the ground line. It will
      blow, but what else is damaged in the process?

      But, the suggestion of eliminating item 1 in your scenario is the
      easiest (and safest) solution.

      Joe M.

      Michael Hopkins wrote:
      > Regarding the starter current story below:
      >
      >
      >
      > If the battery ground wire is missing, seems to me two things are required
      > to make the starter motor current flow to the radio:
      >
      >
      >
      > 1. a ground wire direct from the battery to the radio
      >
      > 2. a ground connection from the radio back to the chassis.
      >
      >
      >
      > Otherwise not only would the starter motor not operate, but no other
      > electrical circuit would function, including the starter relay. The only
      > way I can see to make starter current flow through the XT when you have a
      > direct connection to the battery is to use an external antenna where the
      low
      > side of the antenna is bonded to vehicle chassis - a magnetic mounted
      > antenna wouldn't do it. Even in this case, it assumes the wire to the
      > battery is NOT made out of the same skinny wire that comes with the
      charger.
      > The skinny wire will likely act as a fuse and open up on its own when you
      > try to run >100A through it. But since my antenna is a mag mount with no
      DC
      > connection to the chassis, I'm still safe.
      >
      >
      >
      > I guess if you use a large enough wire size back to the battery AND use an
      > external antenna where the low side is bonded to the chassis (not a mag
      > mount or glass mount) you could burn up PCB track between the DC negative
      > input connector and the antenna connector. I'm only guessing, but I'd bet
      it
      > would happen pretty quick ------
      >
      >
      >
      > Hope this is helpful to someone.
      >
      >
      >
      >
      >
      > Mike Hopkins - K1VLB
      >
      > Home: 603 882 2030
      >
      > Cell: 603 765 3736
      >
      > Mhopkins735@... <mailto:Mhopkins735%40charter.net>
      >
      >
      >
      > From: BCD396XT@yahoogroups.com <mailto:BCD396XT%40yahoogroups.com>
      [mailto:BCD396XT@yahoogroups.com <mailto:BCD396XT%40yahoogroups.com> ] On
      Behalf
      > Of MCH
      > Sent: Sunday, October 07, 2012 6:08 PM
      > To: BCD396XT@yahoogroups.com <mailto:BCD396XT%40yahoogroups.com>
      > Subject: Re: [BCD396XT] Re: Fried It I think
      >
      >
      >
      >
      >
      > If you will only accept an answer from UPMan, that is fine. But, I will
      > tell you that you shorted one side of the speaker to ground and
      > increased the load on the audio amp. Again, if you don't want to believe
      > me that is fine.
      >
      > I will let you know that many radios do not use speakers that are
      > grounded on one side. It may not be common knowledge, but it should be.
      > Never assume anything about radio design.
      >
      > As for speakers, the colors can be anything the manufacturer puts in
      > them. It's usually what is supplied by the speaker manufacturer (who has
      > no idea what they are being connected to). I've seen black/red, two
      > blacks, two whites, two greys, yellow/gray, Etc. Sometimes one side of
      > the speaker was grounded. Often, it is not.
      >
      > Why didn't you use a meter to check the voltages between the points you
      > were connecting? (often if there is a voltage difference it's not a good
      > idea to connect those points)
      >
      > Here is one more common error that ill-informed people do: They connect
      > the ground side of a mobile radio to the battery. NEVER do that. I had a
      > competitor install a commercial two-way radio in a vehicle this way. The
      > vehicle lost the ground between the chassis and the battery. Guess where
      > ALL the starting current went; Right through the radio's ground wire
      > which was the only path left. It literally fried the radio and they are
      > lucky they didn't burn the vehicle up. Just another one of those things
      > that should be common knowledge, but isn't. Some will say if you fuse
      > that like, it makes it OK. It still isn't OK. Just connect the ground
      > side of the radio to the chassis.
      >
      > I know none of this does you any good at this point, but maybe it will
      > help the next person. When in doubt, ask first. I'm pretty sure the
      > manual does say to not ground the speaker.
      >
      > Joe M.
      >
      > radioboy75 wrote:
      >> I realize you said it was a rhetorical question, but I had to respond
      > here.
      >> I guess I would connect it that way because it was my understanding that
      > it IS ground.
      >> Doesn't the black wire on a speaker indicate "ground" and the red,
      > "signal"?
      >> Apparently not . . .
      >>
      >> Some lessons you learn the hard way . . .
      >>
      >> I wish I was more informed about that sort of thing. It doesn't appear to
      > be common knowledge . . .
      >> Perhaps UPman could explain what I did and why I shouldn't do it.
      >>
      >> SVA
      >>
      >>
      >>
      >> ------------------------------------
      >>
      >> Yahoo! Groups Links
      >>
      >>
      >>
      >>
      >
      >
      >
      >
      >
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      >
      >
      >
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      [Non-text portions of this message have been removed]
    • Tony Langdon, VK3JED
      ... If the audio output stage uses a bridged output stage (a common way to increase output power on a limited DC supply voltage), then connecting one side of
      Message 2 of 12 , Oct 9, 2012
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        At 06:19 AM 10/10/2012, you wrote:
        >I'm guessing the problem isn't with the grounding of the speaker but more
        >likely something else since the message comes up saying the voltage is too
        >high (or too low?). Grounding everything together is typically not a bad
        >idea but grounding a speaker wire is typically not done on purpose.

        If the audio output stage uses a bridged output stage (a common way
        to increase output power on a limited DC supply voltage), then
        connecting one side of the speaker to ground will put one of the
        halves of the audio amp across the DC supply, putting stress on that
        output transistor and any voltage regulators in circuit. Another
        potential issue is if voltage regulation takes place on the negative
        side of the supply. In this case, you'd short out the regulator
        and expose the radio to overvoltage.

        73 de VK3JED / VK3IRL
        http://vkradio.com
      • Alex
        ... Illegal voltage will also be displayed if the voltage is too low (I think it appears around 5.0 V, it happens a lot when I power from an external battery
        Message 3 of 12 , Oct 21, 2012
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          --- In BCD396XT@yahoogroups.com, Lance <milcom_chaser@...> wrote:
          >
          > Scott,
          >
          > Can you power the radio up on Alkaline Batteries, no external power source?
          >
          > Illegal Voltage means the source voltage your using is too high...

          "Illegal voltage" will also be displayed if the voltage is too low (I think it appears around 5.0 V, it happens a lot when I power from an external battery that has run low.)
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