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Cobra XL-450 Amplifier

Discussion in 'CB Radio Gear SwapShop' started by FredTx63, Feb 8, 2021.

  1. FredTx63

    FredTx63 Well-Known Member

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    For sale: Cobra XL-450 Amplifier in pretty excellent condition.

    The only real flaw is fixable. For whatever reason, the previous owner decided the engraved labels for the two SO-239 connectors weren't good enough and had to write their labels with a sharpie on the back of the amplifier. This would probably clean of pretty easily. Other than that, it's in excellent condition and does what it's supposed to.

    I've included a picture of the inside, looks all original to me. Too bad the ground strap common to the 4 transistor models of these amplifiers cover the markings on the transistors - look like Toshiba markings to me? Could be 2290s.

    Either way, these are desirable for their effective AB biasing & filtering circuits making them ideal for producing clean output on SSB.

    $300 shipped CONUS prefer PayPal for payment. PM me if you want it.

    s-l1600.jpg
    s-l1600 (4).jpg
    s-l1600 (2).jpg
    s-l1600 (3).jpg
    s-l1600 (1).jpg
    amp9.jpg


     
    S&W357 and Shadetree Mechanic like this.

  2. Sommerkamp

    Sommerkamp Active Member

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    Hi, i am interested in it do you have a phone number so i can call you.Thanks
     
  3. FredTx63

    FredTx63 Well-Known Member

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    Sent you a PM.
     
  4. NZ8N

    NZ8N Well-Known Member

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    M.E.K. will take all or most of the Sharpie markings off. Sometimes Acetone will, too.
     
    FredTx63 likes this.
  5. Big Kahuna

    Big Kahuna Sr. Member

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    Interested as well Fred if Sommerkamp doesn't take it.
     
    FredTx63 likes this.
  6. Cabover Bob

    Cabover Bob Tap tap tap......pay attention

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    Brake clean takes sharpie off......
     
    NZ8N and FredTx63 like this.
  7. techradioman

    techradioman Active Member

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    That one resistor located on the power selector switch is either open(bad) or had severe heating.
     
  8. Robb

    Robb Yup

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    The square blue trimmer pots near the front looks like adjustments for biasing. Not familiar with that amp. But if OEM or not, still a good thing just the same . . .
     
  9. Sommerkamp

    Sommerkamp Active Member

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    Hi, i try call you but your mail is full do you have another phone number i can call you.
     
  10. FredTx63

    FredTx63 Well-Known Member

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    Sommerkamp, never saw a missed call? I'm taking the amp to my tech this weekend to have him check out the discolored resistor pointed out above. Once that is replaced (if necessary) and given a 100% clean bill of health I'll PM you - shouldn't take but the weekend.
     
  11. ButtFuzz

    ButtFuzz Anti-BS Advocate ● WO0WOO ● Reverend Doctor

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    That baked resistor is a casualty of over-drive...
    Why do they put those silly power level switches in there, anyway?
    I am no expert, but the first thing I do when I am re-furb'ing an inexpensive leenyer is pull that prone-to fail / prone to cook mess out of there and bypass it with an adequate wire.

    AND STOP OVER-DRIVING THE AMP.

    Drop the input wattage down lower and let the amp amplify, rather than increasing the input wattage and dropping the input / output with a resistor.
     
    undertaker likes this.
  12. Handy Andy

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

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    The Amp is not made for "10 ohm smoke" it uses 18 ohm - so the Transistor it's paired with, pushes the Base a little higher up from Class C.

    This amp was designed to run low, not as a poor performer, but done up for long-term survival in conditions that may be less than ideal.

    It can explain the reason for the discoloration of the power resistor - chatty people, SSB for Skip - having to repeat the directions to the Doughnut shop - repeatedly - for those needing a sugar rush washed down with caffeine - wear and tear - but @ButtFuzz mentioning the requirement and the proper means to drive it - certainly applies to and for anyone.

    (y):)(y)

    Sure, it may not be stellar power performer - the design puts this into a category by itself - sure - it's gonna' have a little more heat, a little less power, but it has a cleaner output - doesn't make it better dollar per watt wise, it makes it cleaner and better in the Cost of that Watt in the usability and lifetime use in-between Mean Time Between Failures (MTBF).

    If it works, don't fix it.
     
    undertaker and ButtFuzz like this.
  13. Sommerkamp

    Sommerkamp Active Member

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    Hi, did you get the amp check out you said you would you send me a message
     
  14. Sommerkamp

    Sommerkamp Active Member

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    Hi, do you still have the Cobra Amp let me know.Thanks
     
  15. Sommerkamp

    Sommerkamp Active Member

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    Hi, let me know if you change your mind if you want to sell it.Thanks
     

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