Frog Sounds 40m transceiver kit

Discussion in 'QRP Corner' started by K5DH, Feb 6, 2016.

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  1. DL2SBA

    DL2SBA Ham Member QRZ Page

    Hi Dean

    any news on the key click? I've added a small audio cw-filter (check my homepage) and with this, the key click is even more :-/
    What I found is, that the key click depends on the position of the RIT (W2) position? Have you found a similar behaviour?
    Also the key click is not constant during a qso - sometimes more and sometimes less?
    But no one complains about the quality of my signal?!

    Do you have any idea or more research results?

    72s

    Dietmar, DL2SBA
     
  2. OH1LA

    OH1LA Ham Member QRZ Page

    Hey
    I have a problem. The receiver does not work at all. A large part of the machine operates. The transmitter operates. Sidetone oscillator operates. power of the transmitter do not measured, but the FT-2000, S-meter goes to S9 + 60 without antenna.
    Green and red LED will work. The receiver also acts as a crystal oscillator when you listen to another receiver.
    4.7k potentiometer to adjust the crystal. 2kHz up. The receiver does not hear anything, not even a noise. Where the fault could it be?
    73 de Pekka, OH1LA
     
  3. K4YND

    K4YND Ham Member QRZ Page

    great thread. this kit is a no go for someone like me who can build but cant troubleshoot past the most basic issues.
     
  4. K5DH

    K5DH Ham Member QRZ Page

    Pekka,
    Do you have no audio output at all (other than the sidetone), or do you have audio (static) but no radio signals? The sidetone oscillator feeds directly to the headphone output, bypassing the audio amp, so even if there is a problem in the audio amp stage, you will still have sidetone. If there is no audio output at all, then the problem is most likely in the audio amp stage. You may have a bad LM386 chip or other component in the audio amp circuit, perhaps Q2 which acts as a switch. Many builders of these Chinese kits have had problems with bad capacitors, so there may be an open or shorted cap.

    Please let us know what you discover.
     
    Last edited: Apr 8, 2017
  5. OH1LA

    OH1LA Ham Member QRZ Page

     
  6. OH1LA

    OH1LA Ham Member QRZ Page

    Hi Dean
    There is no audio output at all. Only the CW side tone in the headphones.
    Now I do not have spare parts. LM386 pin 6 to the other end of the resistor R2 is approximately 9V.
    Q2 lead pin 1 to pin 3 as a diode
    Could you give instructions to the measurement of the critical places.
    LM386 and other integrated circuits are easy to change as long as I get spare parts.
    Which parts can be ruled out because the transmitter operates as stated earlier.
    73 Pekka, Oh1LA
     
  7. N7EKU

    N7EKU Ham Member QRZ Page

    Hi Pekka,

    It could be that your 2n7000 has been damaged by ESD before it was installed. If so, it would no longer conduct and your receive audio would be permanently muted. Two checks:

    You could measure the A, B, C, and D voltages as reported previously and see if you are getting similar.

    You could just put a clip lead, or short in some other way, across the drain and source leads of the 2n7000 and then see if you have receive audio.

    73,


    Mark.
     
  8. OH1LA

    OH1LA Ham Member QRZ Page

    Hey Mark, Dean etc.
    Sorry for this delay. Now measured the points A, B, C and D. These were measured K5DH earlier.
    The power supply is VASATA P090060-2C1 9V 0,6A. The voltage is 9,3V
    A RX: 8,33V TX: 0,68V
    B RX 8,45V TX: 8,25V
    C RX 4,9V TX: 1,1V
    D RX: 4,17V TX: voltage falls slowly from about 4 volts to zero volts when the transmitter is on.
    How does it affect the voltages? Should 2N7000 bypass jumper wire.
    At point D RX voltage is higher than 4V 9V power supply. K5DH measured 3V 12V power supply.
    Are there any other ideas why did not hear anything?
    73 de Pekka, OH1LA
     
  9. N7EKU

    N7EKU Ham Member QRZ Page

    Hi Pekka,

    I don't see any issues with the voltages. Point C should be set internally by the LM386 chip to about 1/2 of its supplied voltage. The only way DC voltage can be seen at point D I think is if it is from building up a charge on CP9. The voltage built up here I think will depend upon the volume coming out of the audio amp or sidetone generator and the impedance of the headphones.

    You don't even hear white noise in your headphones durning receive? Can you transmit on another rig into a dummy load and see if you can hear it on the Frog Sounds? You can also use a signal generator for this or an antenna analyzer or a grid dip meter. You can also touch your finger to pin 1 of the audio chip and you should here the house hold AC signal.

    There would be no problem to short the drain-source of the FET to see if it is bad. When shorted (bridged) then audio should come through to the phones.

    73,


    Mark.
     
  10. OH1LA

    OH1LA Ham Member QRZ Page

    Hi
    No white noise, nothing of listening.
    Nothing, though to send beside the other transmitter.
    No sound if you touch the LM386 pin 1.
    2N7000 Short-circuit pin 2 to pin 3, between CP5 and CP9?
    What about the pin-1 that goes through CP10? Can 2N7000 to measure? If short-circuits the existence of a risk to break the unbroken 2N7000?
    I have ordered a second series Frog Sound. It comes at the same time new circuits, which may vary from one another.
    I also ordered Pixie II, whose price was less than 3US including postage! It also has a circuit LM386.
    Today is exactly 50-years upon the first connection. QSO was 80m CW band.
    73 de Pekka OH1LA (age 65)
     

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