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MOSFET conversions for upD858 and MB8719 boards

Discussion in 'General CB Services Discussion' started by ExitThirteen, Mar 10, 2011.

  1. Heatwave1972

    Heatwave1972 Member

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    can you please tell me where R209,C200 and L43 is in the uniden washington board PC-385 AH?


     

  2. Heatwave1972

    Heatwave1972 Member

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    that makes since.
     
    #62 Heatwave1972, Oct 14, 2013
    Last edited: Oct 14, 2013
  3. Heatwave1972

    Heatwave1972 Member

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    i like to get help on what 56k onhm looks like also please, trying to do power treak for the president washington that has the 858 chip in it. The First Edition one.
     
  4. Heatwave1972

    Heatwave1972 Member

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    Would You Also Do The Full Convervion Yet? Please Let Me Know.
     
  5. loosecannon

    loosecannon Sr. Member

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    heatwave,

    im a bit confused at what you are trying to do, and i think the reason is that this is a year old thread you are replying to.

    i think the thing to do here is start a new thread in this section, and in your initial post, explain exactly what radio you have, what has already been done to it, whether or not it all works right now, and what exactly you would like to do to it.

    if you will do that, i will try to help you out by letting you know if the mod is worthwhile or not, and how to go about it.
    LC
     
  6. Heatwave1972

    Heatwave1972 Member

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    hi warlock, i have a uniden washington with oriniginal finals and drivers witch is the PC-385 AH Board, but i have the 16 watts 1969 on am and sideband side, witch works absolutly great. then I have another uniden washington Board PC-385 AG and doing mosfets on that one because of i have no other drivers and final's besides 2030's and the 520's . I wish i could get your help about one thing and that is finding out on what the 56k regisiter looks like so then i could finish the president washingtons power treak that is the 858 chip one. it's the first edition one .
     
    Douglas Castejon likes this.
  7. sonoma

    sonoma Sr. Member

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    I was reading this and you ask what the 56k resister looks like. are you asking for some one to take a picture of the part area so you will know where to put the resister on the board at the gate of the irf520 and the far side of L31 I think it was. is this what you are wanting someone to do. it is self explainatory as it is if that is what you are asking for a picture.
    the gate of the final is if you look at it with the writing in the proper position it is the far left leg of the 520. the far leg of L31 I can not tell you since I do not have one here open to look at.
     
    #67 sonoma, Oct 17, 2013
    Last edited: Oct 17, 2013
  8. 9C1Driver

    9C1Driver Sr. Member

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    Dude, this thread is over a year and a half old and if you check his profile Warlock35po has not logged onto the forum since February 2012. I kinda doubt he is going to reply to you. Like it was already suggested, you might start a NEW thread that talks about your specific need.
     
  9. ExitThirteen

    ExitThirteen Grumpy and Cranky

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    Since this thread I've done conversions on the PLL02A SSB boards, many 23 ch. AM/SSB rigs and more recently, the HR2510/2600's.


    ~Cheers~
     
    1 person likes this.
  10. Robb

    Robb Yup

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    Hi Xit13/Rick:

    Thanks for posting this mod. Just installed a MOSFET in this old 5 pin Cobra 148GTL with awesome results!

    Thank You once again!
     

    Attached Files:

    #70 Robb, May 23, 2014
    Last edited: May 23, 2014
    1 person likes this.
  11. ExitThirteen

    ExitThirteen Grumpy and Cranky

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    Hey Robb,

    That resistor looks like a 5.6k ohm, is that what it is? or is it the camera that makes it look like a 5.6k ohm? It should be 56k. Just wondering! :)


    ~Cheers~
     
  12. Robb

    Robb Yup

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    LOL; you are right!
    Didn't find a 56k in my parts bin ATM, but did find a 47k and popped it in there.
    ....wow...

    EDIT:
    Used a 47k and a 10k in series. Fluke says 55.9k ohms. Popped it in already . . .
     
    #72 Robb, May 23, 2014
    Last edited: May 23, 2014
  13. ExitThirteen

    ExitThirteen Grumpy and Cranky

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    Surprised you didn't chernobyl the mosfet. Check the gate for 3.7V or so. You're good at that voltage.



    ~Cheers~
     
  14. Robb

    Robb Yup

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    The bias voltage was 3.75v with the 5.6k resistor and now it is 3.85v with the 56k load. It worked fine then and now. Only time it got warm is when I re-peaked the coils. Runs pretty cool. I'd like to get the gate up to 4v; but that is fixed by the biasing device; right? The MOSFET is a InternationalRectifier IRF-520N. I was going to put in a EKL ERF-2030 that I have in the parts bin. Maybe next time.
     
    #74 Robb, May 23, 2014
    Last edited: May 23, 2014
  15. ExitThirteen

    ExitThirteen Grumpy and Cranky

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    It tends to run too hot if you get the gate voltage at 4V... that's why I backed it off to 3.7-3.8 or so. Eventually I'll make it so it's variable.

    ~Cheers~
     

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