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Cobra 2000gtl internal help!

Discussion in 'CB Radio Modifications' started by RichardHartman, Feb 7, 2019.

  1. RichardHartman

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    I have a 2000 that I am returning back to factory condition. I see that there has been several mods done and I have removed them. I currently am having issues with trying to figure out which wires go to the tone control and the voice lock control. I have very limited knowledge on reading schematics. I have the schematics and the repair manual to research but I am unable to figure out what I need to do. I have located the circut on the schematic but unable to figure out what to do from there. What would be great is if someone could provide some pics of the inside of an original so I could us it for comparison.


     

  2. jon666

    jon666 Sr. Member

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    google is your friend. well not really
     
  3. nomadradio

    nomadradio Analog Retentive

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    I'll see what I can scare up when I get back to the shop next.

    73
     
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  4. 338_MtRushmore

    338_MtRushmore Sr. Member

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    Did you do an image search, or watch any repair videos? I can almost always find the image I am looking for between the two of those. Especially since it isn't an oddball radio.

    Welcome to the forum
     
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  5. loosecannon

    loosecannon Sr. Member

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    start by downloading the service manual here:
    http://www.cbtricks.com/radios/cobra/2000gtl/graphics/cobra_2000gtl_sm.pdf

    (you may have this already, but ill be referring to page numbers so i wanted to make sure)

    the tone control will have a one conductor shielded cable attached to it, with the center conductor going to the center pin (wiper) and the shield going to one of the outer pins.
    if the control works backwards, just move the shield to the other outer pin.

    the other end of the center conductor will go to C77. you will find a hole in the PC board right near C77 and you can confirm on the solder side that this hole connects to one side of C77. the other end of C77 connects to R93, so you'll know to use the end thats not connected to anything.
    Page 24 of the service manual shows C77 to be located on the right side of the board toward the back a bit.
    you will find a hole next to the one you used for the center conductor that goes to PC board ground.
    this is where the other end of the shield will go.

    i'll get to the voice lock later on unless someone beats me to it, as i have to get off the computer for the night.
    LC
     
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  6. nomadradio

    nomadradio Analog Retentive

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    So here is what I found that might help. This was pulled from a junk radio and seems to have all the wires still attached.

    Beware the wires that go to the front-panel lights. Those wires will have different colors from one production run to the next.

    The wires that lead off the the radio's circuitry are probably the right colors to match your radio.

    Probably. No info on the age of the donor radio this came from.

    [​IMG]

    [​IMG]

    [​IMG]

    73
     
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  7. loosecannon

    loosecannon Sr. Member

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    ok, here goes the voice lock control.

    this one is a bit more complicated to extrapolate out from just the schematic, but since i don't have a 2000 in front of me, that's all i have to go by.

    the voice lock is a dual concentric pot, so first i need to point out which terminals control what.
    [​IMG]


    from this we can see that the rear most set of terminals controls the skinny (fine) control, and the front most terminals control the fat (course) control.

    1. solder a jumper wire from one of the outer terminals of the front set, to the middle terminal of the rear set.

    2. run a wire from one of the outer terminals of the rear set to R423 which is located on the switch PC board that nomad posted.

    3. run a wire from the remaining outer terminal of the rear set to the junction of R424 and R425, also located on that switch board.

    4. on the front set of terminals, on the same outer terminal that you soldered the jumper to, run a wire to the unconnected end of R44.

    5. on the front set of terminals, run a wire from the middle terminal to the unconnected end of R174.

    6. on the remaining outer terminal of the front set, run a wire to R175.


    R44, and R174 will be located near the front of the main PC board, just to the left of center.

    R175 will be located on the right side of the board closer to the front from center.

    hopefully some of the wires are already there and you don't have to guess as to which outer terminal to send where, but if the control works backwards, just switch out the connections to the outer terminals.

    of course, you could just find an appropriately sized 20K linear taper pot and just do steps 4, 5, and 6, but then you'd need to find another matching knob.

    hope this helps.
    LC
     
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  8. RichardHartman

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    Wow both you guys (Nomadradio&Loosecanon)were a really big help. Thank you! I have managed my way through tracing the wiring back to the way it was intended. It appears to be only one transistor cut and 3 resistors in the same area as the crystal I just soldered back into the board. The service manual identifies these, I will work on them tomorrow. Thanks again and if I run into any more issues I will definitely ask. 73's

    Thank you 338_MtRushmore this is the first forum I have ever posted and was unsure if I was doing it correctly. It has been a great 1st experience. Thanks again to everyone!
     
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  9. RichardHartman

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    1 more shout out to Mikesradiorepair on Youtube, he has a vast variety of helpful radio repairs posted on this 2000 and what looks to be hundred other ones. Hopefully this string and the videos on youtube will offer someone else some much needed info for those of us who aren't electrical engineer's but appreciate being able or somewhat able to perform repairs on our own rigs.
    https://www.youtube.com/channel/UCfi5fp3qsXeqSbsLAIKU6Dw

    Thanks
    Richard Hartman
     
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  10. 357magnum

    357magnum Sr. Member

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    Welcome to the forum Richard . I said it before & I'll say it again the knowledge of some of the people on here is " Unbelievable " ( Myself not included ):LOL: .
     
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  11. jon666

    jon666 Sr. Member

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    i was going to say something but ill keep it to myself.
    dont want to ruffle any feathers rock on
     
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  12. W2EKG

    W2EKG 201 Mike Action

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    Cobra 2K you say.I didn't think there were any left in existence to do a Super Duper "Restoration?" Why do I think this thread is a bear trap?
     
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  13. jon666

    jon666 Sr. Member

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    yep that is why i say no comment
     
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  14. RichardHartman

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    W2EKG not sure I understand your comment?? I just bought 2000 and didn't know it had mods done to it. I didn't ask my fault. Anyway I just wanted it to be back to original condition its more of a keepsake as a memory of when my dad used to be on the cb when I was a child. He had the 2000 and silver eagle mic, I loved it! When I had the opportunity to get this one at great deal I did. If I decide to pull it down off the shelf and use it I would like it to be ready and legal to transmit on. 73's KC8DVE
     
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  15. 338_MtRushmore

    338_MtRushmore Sr. Member

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    Don't worry, he's just stirring up trouble.
     
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