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I bought a cobra 142 gtl

Discussion in 'General CB Services Discussion' started by red97k1500, Apr 9, 2020.

  1. red97k1500

    red97k1500 Well-Known Member

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    D1962F0D-18E9-4DF4-A5BA-5824632340A1.jpeg 3635D7E7-D051-4B4D-A904-3A9E5055E848.jpeg 34E66202-E662-4B5A-8D98-1CFB7476BB86.jpeg 049786E2-F723-4739-8B24-16744375CEB9.jpeg I bought this 1978 cobra 142 gtl on shop goodwill for $65.00 shipped to my door.
    It was listed as for parts not working all the top cover screws are missing. The ad stated that the unit does not power on. I think they just plugged it into the wall with it switched to dc.

    The radio works, it powers on when plugged into the wall switched to ac. The radio tx/rx’s.
    Dead keys 4 on am, and does 18 on ssb. The meters all work, there not even stuck.



    The only mods that I can tell from spending ten minutes looking at it are.

    Clairifier mod poorly done
    And channel mods
    Two switches on the front speaker of the radio
    Some body swapped in the 11.325 big crystal from a 148 gtl in the x4 spot. Can someone tell me why this is or isn’t the proper thing to do, when channel modding a uniden pc385 chassis radio? I have a feeling it’s Hackery.
    And I should swap it with a 11.3258 crystal.
     

  2. Robb

    Robb Yup

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    Also, check and see if the AM Limiter transistor had been removed. it is a commonly found mod that absolutely ruins SSB tx audio. It takes a 2sc945, a very common transistor found in many radios and other thru hole electronics. That 'mod' is to remove that transistor altogether; the 'fix' is to put another one back in.

    Don't recall ATM the transistor 'TR' number and location; but I'm sure you can find it on CB Tricks. Or someone here on the forum can add that to this thread. I consider that important to fix.
     
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  3. nomadradio

    nomadradio Analog Retentive

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    The date code on the 8719 PLL chip is 1977.

    It's about as old as this model can be.

    The 11.325 crystal works on this radio so long as pin 10 of the PLL is not grounded. The factory-original ground connection on this pin has been removed to make that crystal deliver channels 1-40. You'll need to restore that connection to make the original-type 11.125 crystal work properly.

    For a radio this old to function this well, the mileage must be really low, and it had to have been stored in the proverbial cool, dry place.

    Before long all those electrolytic capacitors will remember how old they are and begin to cause trouble one or three at a time.

    Great find, though just the same.

    73
     
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  4. red97k1500

    red97k1500 Well-Known Member

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    Thanks nomad, there’s very little rust anywhere on this thing, I can’t say there is none, but I was surprised by how clean it was on the inside other than a layer of dust.
     
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  5. kopcicle

    kopcicle Sr. Member

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    The 11.325 is an 11.325, 8-ish crystal. At least all that I have measured are at least 11.3255+
    Original is of course 11.1125
    See the tall , light blue capacitor in the power supply? Just replace it.
    I replaced so many bad ones it became habit.
     
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  6. Handy Andy

    Handy Andy Do Your Research First, Then Decide...

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    You've got a keeper, I see the "Dust Bunnies" added about maybe a 1lb or possibly 2lbs to the Shipping Weight.

    Looks like they kept the covers off, or at least the rear panel side seems to have the worst of the dust collection.

    Definitely at good (if not great) condition - saw your foil side - just with that alone it's a keeper but there is age on that thing - one thing to remember the TA7222AP chip isn't around anymore - so keep the faith and replace those caps so you don't wind up with a board full of 50-50s' - some work while the others don't and it's a crap shoot...

    The biggest concern of the dust - that area is the Goop - The Heat sink goop - when dust collects, that may also attract the other stuff like shavings and other conductive stuff you don't want in there.


    Very rare and lucky find - indeed!
     

    Attached Files:

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  7. 357magnum

    357magnum Sr. Member

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    Great Find ! That was my first SSB radio & I miss it ! Same Mod's ( w/ switches ) same PLL , I talked World Wide 2 cycles ago on it w/ my MR6 ! Nice find !(y):)
     
  8. red97k1500

    red97k1500 Well-Known Member

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    Thanks for the input from everyone, and yes I do plan on recapping this radio, I haven’t decided yet on whether to remove the channel mods or not, I don’t tx out of band. I was actually hoping this thing would be in worse shape than it is lol. The original plan was to put the cheap Chinese freq counter that I removed from the cobra 2000, in place of the front firing speaker on this radio. I also had thought about trying to convert this thing to 10 meters but I don’t think I can ever find the crystal to do that.
     
  9. kopcicle

    kopcicle Sr. Member

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    http://www.jabdog.com/crystals.htm
    11.156mhz get ya within a tenth or so.
    or
    find a 11.6667mhz crystal

    all that has to be done is turn pin 10 high or low accordingly.
     

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