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Galaxy dx959 EPT069610Z help

Discussion in 'CB Radio Modifications' started by Stinkbait, Apr 20, 2018.

  1. Stinkbait

    Stinkbait New Member

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    Hi, this is my first post butt I have read a lot of threads and found most everything I need. I am a retired Electronics tech and have test equipment. Scope, counters, sig gen ect.



    After years of being off the air, I start to notice some antennas on vehicles around and decided to dust off the old rigs and see who’s on nowadays. Now I want to spark up the galaxy 959. It has the EPT069610Z pcb w/RCI8719-99 and MOSFET final. I did all the common stuff, zeners, q55/54, clarifier, alc, etc. But I have some questions about the Dual ERF2030+ Mosfet final mods. All the mods posted are pull this, jumper that, change the other and add the transistors, leaving a lot of empty holes. The dx2517 using the same board, has dual finals with all the holes populated around the second final, VR10/VR11 and so on. LESSCOMM populates these holes when he does the mod but won’t tell anyone the process, charges ridiculous prices and takes months to complete. What’s up with the mods that they don’t need the additional circuitry? All I need is 45 watts of clean signal to drive my amp.
     

  2. ShadeTreeMechanic

    ShadeTreeMechanic 808 On The North Side of Dover

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    Welcome to WWDX! I am not familiar with that radio but I'm sure someone who is will chime in.
    Chris 73s
     
  3. sonoma

    sonoma Sr. Member

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    I have never seen a dual final galaxy 959 to do a full 45 watts. if you whistle or yell into the mic you might see a peak of about that. normally with a dual final radio you will see 12 to 18 watts when just talking.
    here is a link to do the dual mosfet mod with all the holes filled in as you call it. a few will still be empty as a few parts are not needed. hope this puts you in the right direction. but you will not get 45 watts of talking power out of it. you will have a little more out put if you use the 13n10 mosfets and not the irf520 shown. the 13n10 uses all the same parts the 520 does.

    http://www.cbtricks.com/miscellaneous/fet_papers/mosfet_conv/graphics/6900xxx_ssb_mosfet.pdf
     
    #3 sonoma, Apr 20, 2018
    Last edited: Apr 20, 2018
  4. Stinkbait

    Stinkbait New Member

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    Thanks for that, I was searching under model rather PCB numbers. However the gain would not even be noticeable.
    I take it you favor the 520's over the EKL mosfet's? The ERF2030+ is suppose to be an upgrade to old 2030 but I haven't found a data sheet for them yet. They rate them oddly like "30 whats of PEP" rather than watts of dissipation. Apparently a marketing tactic. The rig has 2sc1969 in it now and a 520 driver.
    I think I'm better off with a good foot warmer rather than a hot radio.
     
    ShadeTreeMechanic likes this.
  5. sonoma

    sonoma Sr. Member

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    I like the 13n10 fet myself. either of the 3 will work fine. just I have seen a little more out of the 13n10 fets so far. .
    if you are needing 45 watts drive you will need a bigger radio or a small amp to drive what ever you need the 45 watts to feed it.
    HAGO
     
  6. Stinkbait

    Stinkbait New Member

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    Yea, I'm gonna swap out the one final and find a better amp.

    I'm also having problems with the clairifier mod. I tried all the tricks, R153 to 10ohm, c130 to 4pf. installed a 10turn 10k pot with a counter knob. Pot is 8v constant top(J9 pin1), dc ground bottom, D38/R114 shorted, D68/R113 gone so center wiper goes to RIT control ckt only. But it wont slide but 1kc. Doesn't even move the counter on the radio, I have to use a 6digit to see it. For now I put the slide mods back to stock and left it tx/rx locked.
     
  7. Stinkbait

    Stinkbait New Member

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    This is a simplified drawing of the clairfier CKT. Problem is little or no slide,
    Questions:
    1: Is 10k pot too much? 1k is stock, PLL was aligned in the center(5k) position.
    2: C130 to 4pF seems extreme and may be causing (or adding to) stability problems. The radio drifts somewhat anyway and this can't be helping it any.
    3: Why jumper D38? DC current should flow right thru it. Minimal Voltage drop and was there for locked claifier for a reason.

    I will make some voltage measurements the next time it's on the bench but other than this, It's working great and I need to travel with it.

    upload_2018-4-20_21-19-12.png
     
  8. nomadradio

    nomadradio Analog Retentive

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    What's going on in this circuit when it is still factory-stock is to alter, or "pull" the resonant frequency of the crystal. The varactor diode D49 changes capacitance, with the DC voltage you put across it. Highest capacitance at the lowest clarifier voltage, lower as the voltage rises.

    The purpose served by C130 is to set a minimum circuit capacitance when the varactor voltage as at its max. Since the capacitance of the parallel pair of D49+C130 adds up to the sum of both, C130 sets the minimum. This sum-total capacitance is in series with the crystal and it will cause the level of feedback current through the crystal to change along with the resonant frequency. The smaller the capacitance in series with the crystal, the higher the reactance (resistance to AC-current flow) becomes. The higher the reactance, the smaller the AC current through the crystal. There will be an upper limit to this, when the current through the crystal is reduced below the minimum needed to make it oscillate.

    And that's what you see when you make C130 too small. The frequency will become unstable when there isn't enough feedback current through the crystal.

    73
     
  9. Stinkbait

    Stinkbait New Member

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    OK, good stuff. So we put c130 back to 20p(it already is btw) or go to 10pf for balance, and change the variactor to a NTE614(33pf @ 4v). What works best? I see alot of different of mods on this.
     
  10. nomadradio

    nomadradio Analog Retentive

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    This is strictly a 'cut-and-try' sort of exercise.

    I would start first with an objective to aim for.

    Are you trying to see how far it will stretch without shutting down?

    The upper limits will never be exactly the same from one radio to the next.

    Swapping the crystal can reveal a difference. Some crystals are "hotter" than others, and will stretch farther before cutting out.

    No good way to predict this that I know, other than to try.

    73
     
  11. loosecannon

    loosecannon Sr. Member

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    i believe i posted a dual mosfet final mod for the 959 on this forum about 10 years ago.

    i did it by comparing the schematics of the 2517 and the 959 and it does work.

    there is a jumper you have to add, and there is a coil with 7 turns that needs to be changed to 4 turns, but i cant remember the mod exactly.

    using 520's i was able to see 40-50 watts PEP out of the radio, but you really need to add an external heatsink after doing this mod, as the radio gets hot quick.
    LC
     
  12. Stinkbait

    Stinkbait New Member

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    Thanks for pointing me there. I found the thread you mention, It spans over 7 years, lol. There is alot of info but no real practical answers. I like the idea because it looks neat and clean as opposed to having gadgets and wires hanging about. It was exactly what I wanted to do, however to re-engineer a working radio for a few watts , is not what I bargained for. Over all, about a 3db gain over re-tuned stock if you leave room for swing. A 100w bolt on kit would get me 6db and their cheep.
     
  13. Low_Boy

    Low_Boy Active Member

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  14. Stinkbait

    Stinkbait New Member

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    Yes. That was posted above and referenced in looscannon's 7 year thread. In That thread he basically warned that a tedious radio alignment and balance procedure was required to calibrate the 2 mosfets and new additional circuitry in a radio that was not designed to have them. Several tried and just burned up a bunch of parts, others couldn't get it to do any more than the single final version. That cbTricks article, in fact ,was written for the purpose of upgrading a bipolar board to Mosfets back during the changeover period when both versions were on the shelf, and is not a change to dual mod. The common dual mosfet mods avoid all that by just piggy backing the second final to existing circuitry so it looks to the radio as one big final. That it is why it is easy to do but offers little gain.
    I'm assuming the single final design is operating class A where as most 2 pill amps operate in Class AB (or push/pull).
     
    #14 Stinkbait, Apr 21, 2018
    Last edited: Apr 21, 2018
  15. loosecannon

    loosecannon Sr. Member

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    "the 7 year thread" LOL

    i agree completely stinkbait. i only did the mod to see if it could be done, and honestly, i only ever ended up doing it to a very small number of radios for others, and interest in that mod quickly dropped off.

    the only reason i could see for someone to want it done is that they were in love with their DX959 and wanted to run a big amp after it.

    your best bang for the buck is either a 2 pill or a 4 pill amp, whichever you get a better deal on, as their outputs will be within 1 s-unit of eachother.

    good luck in your amp search!
    if you see a forum member selling one here, that is most likely going to be your best bet, as long as they are an established member and not a fly by nighter.
    LC
     
    ShadeTreeMechanic likes this.

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