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New Galaxy DX2547 with IRF520 Mosfet finals

Discussion in 'CB Radio Modifications' started by movrider, Dec 17, 2009.

  1. movrider

    movrider Member

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    Question on the Dual final mod for the Galaxy DX2547 with IRF520 mosfet...
    All the info I am finding on this is for replacing 2SC1969 transistors with ERF2030 mosfets, My radio came stock with the single IRF520 mosfet, would like info (details) on converting this specific setup to dual mosfet finals if it has been done and what I might expect to see out of the radio for the trouble. would the RFX75 Powerband driver be a better choice and will it work with the Galaxy DX2547 mosfet version. would the variable power still work? My plan is to use the Galaxy to drive a transistor type base amp that will take from 4 to 25w for a driver.



    Thanks for any input
    851 in the Southeast Buckeye
     

  2. TonyV225

    TonyV225 W9WDX Amateur Radio Club Member

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    You would have top use an external power source ( power supply) if you used the rfx add on because the internal supply would probally die from abuse. You would also need to change the fuse in the mobile style power cord to handle the intake.

    That Galaxy 2547 radio should do 20 - 25 watts easily and 20 watts is plenty to run into your amplifer on SSB without pounding the hell outta the amplifier aswell. You have to becareful when messing with power modifications you can start running into problems with dirty signal which an amplifier will do just what its supposed to and thats amplify that dirty signal .

    It would be a shame to go through all the extra work to find that there are glitches such as messy audio ETC. If that radio sounds good and clean Ide just leave it alone and run it as it is the few extra watts you would gain from your amp by feeding it more power is something nobodys going to notice on the other end unless ofcourse it gets muddy sounding.
     
  3. Robb

    Robb Yup

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    I agree 100% with that.

    If you want 4 -25 watts to drive an amp; make no further modifications. As Tony pointed out, your radio's power supply would be overtaxed and eventually fail. Better to ante up for the right amp and a power supply that will fill the bill.

    How big of an amp did you intend to run?
     
    #3 Robb, Dec 17, 2009
    Last edited: Dec 18, 2009
    Staybolt likes this.
  4. 555

    555 Active Member

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    how about you leave the finals alone and have deadkeying 2 watts and let is swing
    and i will send you a 300 watt base amp for 100.00 plus 25.00 ship tube type amp
     
    Staybolt likes this.
  5. TonyV225

    TonyV225 W9WDX Amateur Radio Club Member

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    THERE YA GO!!!
     
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  6. Robb

    Robb Yup

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    Wow - a tube amp at that!
    Too cool...
     
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  7. movrider

    movrider Member

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    Sounds like a good deal on the 300 watt tuber but I am afraid momma would shoot me if another package shows up at the door...lol!

    Just looking to get a little more out of the Galaxy to cut thru the local trash, was thinking a swing of 45-50 should be possible will the dual finals and would be great when needed. I am doing that now with a two stage Silver Bullet 50-100 on a 10 amp PS. but would like to move that amp to my truck with the DX959.

    Looking at RM Italy BLA300+ have heard good things about the filtering and read good reports driving it with up to 20 w

    If I need to get a little more serious I could dust off the vintage Golden Eagle 750 and President Madison or the Washington or warm up the old Browning Eagle.;)
     
  8. Ridgerunner0788

    Ridgerunner0788 New Member

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    I am working on a Galaxy 2547 and it had the irf 520 in it I replace then with the irf 520 N what do I have to do to get the radio to transmit it receive every one but doesn't trans mit on frequency , or is my power supply not big enough to run it I have it on a 10 amp power supply , when I key everything dims on the radio and is off frequency thanks for you're help .
     
  9. Shadetree Mechanic

    Shadetree Mechanic 808 On The North Side of Dover

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    If the lights dim then you need more power. Hook a volt meter up and see what it reads when you key.
     
  10. Ridgerunner0788

    Ridgerunner0788 New Member

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    How do ya check the voltage at the final and driver and how do ya adjust it
     
  11. Shadetree Mechanic

    Shadetree Mechanic 808 On The North Side of Dover

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    What I meant was to measure the voltage of the power supply while being keyed. Maybe there is something wrong with the power supply?
     
  12. Handy Andy

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

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    Well, you raising a lot of questions...

    Well, now we need to understand why you replaced the IRF 520 with another IRF520-N

    IF the radio didn't work and you replaced the final - the DX2547 uses an AM regulator transistor too, to power that part and modulate it.

    IF the AM Regulator is toast, replacing the final = it's still toast.

    Ok, lets look a little more into this...

    Was the Receive working before you did this - you say it works now - did it work just as well before or was other work done to it besides the IRF 520 swap? (I'm looking for to see if you may have forgotten a step to make the TX work because of Receiver issues - like replacing the Mirror Test Point Jumper board )

    (Graphics Courtesy of CB Tricks)
    DX2547Testpointjumper.jpg

    So if you simply fixed a Final - re-check your work. Make sure you didn't cause any more damage by causing shorts from bad soldering.

    FOR SAFETY - USE - INSTALL 50 OHM DUMMY LOAD RESISTOR on the antenna jack to prevent further damages cause by high SWR mismatch

    Grab a DVM - using test leads, REMOVE TEST POINT JUMPER board - SET/CLIP POSITIVE lead on to TP 7 and use NEGATIVE lead for your SOURCE FROM TP & THRU METERS AMMETER SETTING INTO the negative lead...

    Now, as far as who or what to do - See VR 10 above? That is the trimpot for the Final - set Negative Clip on TP8 it using your DVM set for mA - about 35mA - no more - if you cannot set it for that - then STOP and re-check for shorts.

    You do the same for the Driver VR12 using TP7 - for safety. Again 35mA. Negative Clip to TP9

    Replace Mirror Test Point Jumper Board (reconnect the AM Regulator to feed Driver and Final)

    NOW IF AM REGULATOR IS DAMAGED - you would have one of two things happen; you get carrier power with NO AM audio - but SSB and FM modes would work (AM Regulator Blown Shorted) - OR - you have nothing because the AM regulator has a catastrophic failure (Blown open)

    Choose your poison.
     
  13. W2EKG

    W2EKG 201 Mike Action

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    Would a Mean Well supply fit in the cabinet?
     
  14. Ridgerunner0788

    Ridgerunner0788 New Member

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    Sorry it took me so long to get back to ya handy Andy I replaced the final and driver to the Irf 520 N because I wasn't getting any watts out of it , also only about 20 percent modulation , I figured replaceing the final and driver would help , but I guess I was wrong what it had in it was just irf520 for driver and final
     
  15. Handy Andy

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

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    Did you have a chance to review the post?

    IF you were able to adjust the mA draw, but still no power - the AM regulator - did you check it?

    We also need to look at other less obvious;" but boy we'd look stupid if we forgot about them" things to check for...

    Does the RX/TX light go from Green on RX to Red on TX?

    Does the Test trip show any voltage? In AM about 5.6 Volts or so for AM POWER...if you don't get any voltage you may have a burned up power feed line or AM regulator is toast.

    Bad soldering on the bottom of the board - cold soldering joints?

    Did it just need a good tune up?
     
    NZ8N likes this.

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