1. You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.
    Dismiss Notice

MOSFET conversions for upD858 and MB8719 boards

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

  1. liquidh8

    liquidh8 Active Member

    Joined:
    Aug 7, 2011
    Messages:
    271
    Likes Received:
    7
    Ok, now that I have it fixed again, I'll do the conversion again, and take a few pics. I wonder if my 858 is a different board?


     

  2. ExitThirteen

    ExitThirteen Grumpy and Cranky

    Joined:
    Apr 18, 2008
    Messages:
    1,835
    Likes Received:
    1,222
    Shouldn't be... I can take pics of my Washington inside, and show you what mine looks like.



    ~Cheers~
     
  3. liquidh8

    liquidh8 Active Member

    Joined:
    Aug 7, 2011
    Messages:
    271
    Likes Received:
    7
    ok cool, thank you
     
  4. liquidh8

    liquidh8 Active Member

    Joined:
    Aug 7, 2011
    Messages:
    271
    Likes Received:
    7
    Did you even get a chance to snap a few of those pics? I am still having issues with this Washington, good thing I have the Saturn to talk on. I would like to convert the driver and finals to mosfets, cheaper. The 1306 and 1307 are long gone. I think when I did the conversion at first, I have a different circuit than u. Seems someone before changed a few things. I have a factory schematic, but I am almost afraid to put it back to the schematic. :mad: The driver and final circuit look like a cross between a 139lxr service bulletin and stock.

    I plan on ordering the parts and trying it exactly like the schematic says, but it doesn't include the 47Ohm resistor from the base to ground on the schematic. :mad:

    Anyhow, if you could take a few good pics of what you have I would appreciate it! Thank you
     
  5. psycho

    psycho Running a special on our rooms!

    Joined:
    Aug 25, 2006
    Messages:
    3,440
    Likes Received:
    1,262

    $15-$20 is too much for a 2SC1969? I would pay that any day instead of a mosfet conversion for $4. You will go through 6-12 mosfet finals before blowing a 1969.
     
    2 people like this.
  6. mr_fx

    mr_fx Sr. Member

    Joined:
    Oct 8, 2011
    Messages:
    1,537
    Likes Received:
    168
    I still don't see the problem even if that was the case... You can buy 25 International Rectifier IRF520 mosfets for around $15 SHIPPED... in general most radios only need a handful of inexpensive parts to get up and running... and USUALLY you will see better numbers on the meter. In some cases even doubling peak power output.

    I mean let's say that you have an Cobra 29 LTD. In this 29, you install a 2sc1969 and let's say you get 25-30 peak... On the same radio with an IRF520, and the correct companion parts, guys are getting 35 on the low end and as much as 50 watts on the high end.

    To me that seems like a good reason to look at mosfets. My personal best on a mosfet Cobra 29 was 48 watts. (last I heard it was still working and the owner is quite proud of it.) Mosfets run pretty cool from what I have seen. They are also dirt cheap even for the quality ones.

    Another thing to consider is as of late China has been working very hard to produce FAKE NEC 1307 and 2sc1969 finals. I have even seen some that were 'NEW', but it was easy to tell that they had just been carefully cleaned up and sold as new.

    If you go with mosfets, just make sure you buy from a quality company and a quality brand, I normally go through Jameco. Further more make sure you use the correct companion parts. As for old school transistors, just make sure they are real and there is nothing to worry about.

    Either way, eventually you will not have a choice, eventually the transistor, like the dinosaurs will simply go extinct.


    ALSO this might be useful to some of you guys. The EKL parts are quick and usually get you close, but sometimes you get better results by changing a few values.

    CBTricks MOSFET Experimenter's Information Notes
     
  7. mackmobile43

    mackmobile43 Jock Supporter

    Joined:
    Feb 11, 2008
    Messages:
    6,709
    Likes Received:
    382
    POO POO ON YOUR MOSFETS
     
  8. mr_fx

    mr_fx Sr. Member

    Joined:
    Oct 8, 2011
    Messages:
    1,537
    Likes Received:
    168
    lol, to each their own. But you should just get used to it. Transistors are on their way out
     
    1 person likes this.
  9. GnG8d

    GnG8d Well-Known Member

    Joined:
    Jun 28, 2010
    Messages:
    2,037
    Likes Received:
    328
    What's all this talk of "companion" parts?


    Sent from my iPhone using Tapatalk
     
  10. GnG8d

    GnG8d Well-Known Member

    Joined:
    Jun 28, 2010
    Messages:
    2,037
    Likes Received:
    328
    And why does everybody talk like fet technology is new?


    Sent from my iPhone using Tapatalk
     
  11. NorthStar

    NorthStar Administrator

    Joined:
    Mar 21, 2005
    Messages:
    1,354
    Likes Received:
    29
    It's new to alot of CB ops!
     
  12. Robb

    Robb Yup

    Joined:
    Dec 18, 2008
    Messages:
    11,139
    Likes Received:
    2,876
    Think he was talking about these:

    [​IMG]

    These are the 'companion parts' that are needed to make the MOSFET work.

    CBTricks MOSFET Experimenter's Information Notes

    Since the Eleflow company now makes the CB-20w/2SC1969 as a replacement part, MOSFETS aren't all that necessary to use. But it is still nice to know there is an option just the same . . .
     
  13. GnG8d

    GnG8d Well-Known Member

    Joined:
    Jun 28, 2010
    Messages:
    2,037
    Likes Received:
    328
    I just found the emphasis in all the posts a little humorous.


    Sent from my iPhone using Tapatalk
     
    2 people like this.
  14. ExitThirteen

    ExitThirteen Grumpy and Cranky

    Joined:
    Apr 18, 2008
    Messages:
    1,835
    Likes Received:
    1,222
    Yes, Robb is correct. Those are the companion parts that I am speaking of. They can be bought thru Copper, H&Y, RF Parts and some CB shops.

    I've been doing MOSFET mods on these boards for a few years now, but I wasn't going to post information about it if I didn't think it wouldn't be reliable, or if the mods caused the radio to perform poorly. Certainly nothing new, but useful if someone wanted to experiment, or wanted to keep costs down when replacing finals.

    The first D858 Washington I did is still in service today, it's been over 3 years. Still sounds good, still puts out about 25W on SSB.


    ~Cheers~
     
  15. 2RT307

    2RT307 Sr. Member

    Joined:
    Nov 22, 2011
    Messages:
    2,307
    Likes Received:
    753
    Good stuff, ExitThirteen. Like it or not, MOSFETS, along with SMT, are the wave of the future.

    Thanks for sharing.

    73,
    RT307
     
    1 person likes this.

Share This Page

  • About Us

    The WorldwideDX Radio Forum was originally established in 2001. We pride ourselves on welcoming Radio Hobby enthusiasts of all types, while offering unbiased, informative, and friendly discussion among the members. We are working every day to make sure our community is the best Radio Hobbyist's site.
  • Like us on Facebook

  • Premium VIP Member

    The management works very hard to make sure the community is running the best software, best designs, and all the other bells and whistles. Care to buy us a beer? We'd really appreciate it!

    Donate to us!