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Transistor upgrade

Discussion in 'CB Radio Modifications' started by Larry A McClanahan, Nov 10, 2018 at 5:25 AM.

  1. Larry A McClanahan

    Larry A McClanahan Active Member

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    Does anyone know if there is an upgrade transistor for the RCI Ranger 2990 power supply. It uses two 2n6328's.


     

  2. rabbiporkchop

    rabbiporkchop Well-Known Member

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    Not sure about an upgrade, but the 2N6331 should work just fine.
     
  3. sp5it

    sp5it Master of puppets

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    What for? It is 30A collector current transistor. 2 paralel make 60A, that is big margin for 150W radio.
    Mike
     
    Larry A McClanahan likes this.
  4. Tallman

    Tallman W9WDX Amateur Radio Member, KW4YJ EXTRA class

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    Some times the best modification is none.
     
  5. jon666

    jon666 Sr. Member

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    if it aint broke dont fix it. everyone is tinkering.then wonder why it dont work anymore
     
  6. Martian

    Martian Active Member

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    People that try this stuff with linear power supplies are almost always after one of two mystical creatures that can be proofed long before you even think about swapping parts:
    1. More power
    2 Cooler operation

    They see something like more current handling and think.. more power, or it must run cooler!
    Or, the device being able to dissipate more heat.
    Or...... larger package.
    (which people think means it will run cooler - but in fact it will just get to temperature faster because of it's improved thermal transfer)

    If they did the math they would quickly realize that changing the devices will result in little to no gain. There may in fact be loss in the process. You make the problem worse.

    The changing of regulators in virtually every case that I have seen or read about resulted in either zero or negative gains and every single time because the math just did not work.

    Lest we get into how to properly de-rate the devices , which none of them even consider. Too much maths.... I want moar powah and watts!

    You got it. In a case like this, no mod is better.
    UNLESS..... it's one of:
    1. reduced load
    2. larger heatsink
    3. design changes

    And.. none of these are practical.
     
    Tallman likes this.
  7. Tallman

    Tallman W9WDX Amateur Radio Member, KW4YJ EXTRA class

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    Plus most people do not understand "Compensation Networks" well enough to get the maximum out of the circuits. When you change a component that has a large effect on the regulation and response times are affected. Power supply switching noise could increase to the point of making it unusable.
     
  8. Shockwave

    Shockwave Sr. Member

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    When these transistors fail it's usually not from too much current. At 60 amps you're not likely to damage them from current unless you short the supply and the caps discharge through the pass transistors. Failures are almost always related to improper installation at the factory. I can't tell you how many times I've found parts mounted to the heat sink with loose hardware or little to no heat sink compound behind them.
     
    kaos513 and Tallman like this.
  9. nomadradio

    nomadradio Analog Retentive

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    We stopped repairing that power supply when the 30-Amp "brick" switchmode supplies dropped below 50 bucks.

    Like this one:
    https://www.ebay.com/itm/350W-Meanw...a5dade57:m:ma5yeFIs1QDEOhsB7n6suGg:rk:10:pf:0

    This is what the factory uses in all of the 2995 base radios made in the last ten years or more.

    It has two advantages. First, it has overvoltage protection. The original power supply with the heavy transformer does not. When those power transistors fail, they can fail as a short circuit. This puts up to 25 Volts DC onto the 12-Volt radio and linear. Things pop, not the least of which is the CPU/display board.

    Second, it has a current limit. The original supply does not. The advantage of this feature is that the switchmode supply will protect itself if the radio draws excessive current.

    Have you powered this radio from an external power supply yet?

    If the power supply has failed, it's prudent to make sure the radio or linear doesn't have a fault that overloaded it and caused the old power supply to fail. Might want to know the full extent of the failure before you remove the old power transformer and supply, then install a new switchmode brick.

    73
     
  10. Shockwave

    Shockwave Sr. Member

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    I'll bet that idea makes the back of the radio run a lot cooler too with those pass transistors no longer heating it.
     
  11. Handy Andy

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

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    It's just the older Linear power supply versus the Switching style.

    Linear consumes a lot more power to keep caps charged and dissipate heat from the dropping voltage across the pass transistors - all the time.

    The newer design replacement makes more sense as it works like power on demand versus the constant regulation and loss in heating and cycling the older Linear design required.

    Oh well...
    Found a Darlington pair 160 WATT (Not amperes) in a top hat TO-3 design. PDF attached.

    One word of note though, if you think about it - the part in the PDF would make a dynamite replacement drop in for the AM regulator - in a TO-3 design (or TO-204 style) - it has an Hfe of close to 4MHz so it's well suited for Audio passband.

    So if you're looking into replacing the typical AM regulator - this part can suffice for driving the 9530

    (forgot to attach the PDF! Sorry 'bout that!)
     

    Attached Files:

    #11 Handy Andy, Nov 13, 2018 at 2:09 PM
    Last edited: Nov 13, 2018 at 7:13 PM

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