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7010RE: [BCD396XT] Re: Fried It I think

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  • Michael Hopkins
    Oct 9, 2012
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      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.

      Shorting out the speaker probably wouldn't kill the unit. It's possible, but
      audio outputs are often transformer coupled and floating, so grounding one
      side or the other likely wouldn't hurt anything. I certainly wouldn't ground
      one side of the speaker anyway since it wouldn't do you any good anyway. On
      my XT, the low side is NOT grounded, so it's likely floating but may get
      grounded somehow back through the low side of my computer audio input jack
      or the audio input connection on an amplified speaker - don't know; haven't

      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


      From: BCD396XT@yahoogroups.com [mailto:BCD396XT@yahoogroups.com] On Behalf
      Of MCH
      Sent: Sunday, October 07, 2012 6:08 PM
      To: BCD396XT@yahoogroups.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
      > 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,
      > 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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