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Stinger Board Real Output??

Discussion in 'CB and Export Equipment and Accessories' started by Plumber-G, Sep 15, 2018.

  1. Plumber-G

    Plumber-G Plumber-G

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    So I have this stinger AD203 Board ,been laying around in my junk box so I decided to check it out. According to stuff on the web it's supposed to output 160 watts with a 3 1/2 watt input. I read some of the posts on this site and if I got 60 watts, I should be happy. and I would be<GRIN>



    So here is what I have, let me know what you think

    Radio SBE Trinidad III 3 watts out swings to about 6 watts
    Power supply to amp only 75 amps
    Mic input 1000Hz signal 5 millivolts

    Amp output carrier only 9 watts
    Amp out with 1000Hz modulation 18 watts

    If I raise the mic input the modulation starts to flat top,
    Another question what should the voltage output on a NON power mike be?

    I have the schematic for the amp here Stinger-Board.jpg

    Thanks Plumber-G
     

  2. Robb

    Robb Yup

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    How are you measuring power?
    eg: watt meter and dummy load or watt meter and antenna?

    Is it new?

    Doesn't look like it has any output at all. Either the fuse is toast, the mosfets are fried, or the relay isn't working right - even if you hear it clicking.
     
  3. Plumber-G

    Plumber-G Plumber-G

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    I measuring though a pep wattmeter to a dummy load
    I am getting triple the input but I would assume it should produce more

    Tried checking the mosfets with a ohm meter appeared to be OK but not 100% sure I was doing it right
     
  4. Robb

    Robb Yup

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    Four RM3 mosfets should make ~30w PEP/ea; so it should have ~120w PEP if driven properly.
     
  5. Plumber-G

    Plumber-G Plumber-G

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    Sounds like I could have 3 Mosfets bad??
    What is the best way to test them?
    Can it be done without removing from board

    Heat sink does get hot when transmitting, takes a minute

    Appreciate all the help
     
  6. kaos513

    kaos513 Well-Known Member

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    Measure voltages of each mofset
     
  7. Robb

    Robb Yup

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    Mosfets tend to get a bit fried-looking if they are bad. Not always, but often enough. Did you look at them yet?

    Testing mosfets is a bit tricky and not at all like testing a bipolar transistor. If they use the common IRF-520N like radios use (probably); then they are about $1.25/ea to replace. Replace all four.
     
  8. Plumber-G

    Plumber-G Plumber-G

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    I measured voltage at each mosfet and they were all the same:
    Gate (-1.95)
    Drain 13.2v
    Source 0

    I am having trouble understanding what is happening? wouldn't we want a positive voltage on the gate??
     
  9. kaos513

    kaos513 Well-Known Member

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    Test all your diodes on the board
     
  10. kaos513

    kaos513 Well-Known Member

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    Test mosfet with power off there in series and you may not get the correct readings
     
  11. Plumber-G

    Plumber-G Plumber-G

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    Diode D6 looks a little iffy rest of diodes checked out fine

    Power on recieve
    Gate (-0.12)
    Drain 13.2v
    Source 0

    Power on transmit on
    Gate (-1.95)
    Drain 13.2v
    Source 0
     
  12. kaos513

    kaos513 Well-Known Member

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    Check d6 with meter on continuity mode .
     
  13. Handy Andy

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

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    Review your schematic...

    The power you see as negative, is rectified power from the RF coming into the Amp from your radio. Note the unbanded side of the diodes on the input ACROSS to a set of caps - they provide the working mechanism for the amps Class C operation.

    The Gates themselves just need a field effect or voltage presence - can be positive or negative, so as the carrier power develops - the incoming unmolested power that is RF passing thru the, now - slightly negative, voltage bias presence - helps the transistor "transition" from on to off state.

    What is nice about this method is the effort to keep the ratios of power in both negative DC range (BIAS) and the positive drive level RF is (in reference to ground) from skewing the transistor and causing a latching issue from too much positive drive on an ,AC waveform.

    Without this offset, it can generate an FM effect - the reverse bias the diodes create is short lived and only exist as a ratio of power - as in - the Rectified negative region to the positive RF level of drive - so the Gates don't see a ton of RF power and possibly damaging the gates from perforation (puncture) thru into the substrate - making it a dead short instead.

    So, you asked about Mic's...

    Well, Mic's can be found in two categories,

    One called Dynamic - generate their own signal as an AC component and are very low-level - like 600mV (about 0.6 VAC) - Dynamic sounds more "official" than "Generates their own power".

    Another is Electret - they use power called BIAS - it's essentially a voltage with very low-current behind it - the Element in an Electret is a membrane over a fixed plate - and then you talk the membrane vibrates and changes the distance it has to the fixed plate - making it act like a variable capacitor - an FET amp inside the Element detects this and amplifies the effect (your voice) as a ratio of power in to power out - per the IMPEDANCE the source of voltage is to power the device.

    So ...

    Dynamics are 600 ohms to about 1K (1,000 ohms) and generate their own power. They are a lot like Speakers, they have a coil and magnet - the membrane is attached to the coil that vibrates s you talk, and the coil is suspended over the magnets poles and the coil vibrates thru the field - generating a current with a low-voltage component to it.

    Electrets are 1K (1,000 ohms) or higher and require the radio to supply the power or have a battery to get their source of power from. And most FET amps use less an 5 VDC and require an Source Resistor from the Power (or Impedance) of about 2.2K (2,200 Ohms) on up to 5.6K (5,600 Ohms) to properly develop a signal that can pass thru the power source into a Blocking cap and what appears at the output - is your audio signal minus the bias power used for the FET amp in the electret.

    Dynamic can be considered more of a Current Sourcing device having a low-voltage component and Electrets are more Voltage Sourcing with little current available - component.

    Hope this helps drain some of the muck...

    Still clear as mud right?


    The above is very - very basic but I hope it helps you more in understanding that Loud is not always better...
     
    #13 Handy Andy, Sep 16, 2018
    Last edited: Sep 17, 2018
    Shadetree Mechanic likes this.
  14. milkman21218

    milkman21218 W9WDX Amateur Radio Club Member

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    Try this,
    You will not be able to run the board in the radio after you do the mod
    Put a 10 amp fuse in the AD-203 and in the hot feeding the radio
    Cut one side of R2. Put a jumper across R3 & R4
    DK 2 1/2 to 3 Watts in to it
    You should see 40 DK and a swing to about 130 watts.
     
  15. Plumber-G

    Plumber-G Plumber-G

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    D6 checked out
    Do you think I should pull and check the mosfets and check??
    If I pull them I guess I should replace them??

    Thanks
    Plumber-G
     

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