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ft-8900 no 2m TX

Discussion in 'Radio Circuits, Repair & Performance' started by N1EBC, Oct 10, 2021.

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  1. W1NB

    W1NB XML Subscriber QRZ Page


    How much RF are you seeing on the output of the final?
     
  2. N1EBC

    N1EBC Ham Member QRZ Page

    Looks like about 11v rms.

    jason
    N1EBC
     
  3. K7JEM

    K7JEM Ham Member QRZ Page

    I traced out the signal path, and it goes through some relays after the power amplifier. If the unit is drawing a few amps of current, it is likely that things are good up to the power amp (but not certain). You could have a relay problem or something else going on. The fact that it works on other bands indicates that the final is working, but probably something else in the path.

    upload_2021-10-12_19-37-34.png
     
  4. KA9JLM

    KA9JLM Ham Member QRZ Page

    Command failure is the relay.
     
  5. N1EBC

    N1EBC Ham Member QRZ Page

    Before Ijust replace the relay. I check for signal before and after the relay. An verify voltage at the relay then report back.
    Thanks for the help
    Jason
    N1EBC
     
  6. N1EBC

    N1EBC Ham Member QRZ Page

    So i get signal at l1105 but no signal at l1107 so it looks like rL1002 is stuck.
    I can't seem to find d1113 or d117 to check the voltage on the relay.

    g5a-237p relays I cannot seem to find a replacement anyone have an alternative?

    Thanks
    Jason
    N1EBC
     
  7. K7JEM

    K7JEM Ham Member QRZ Page

    Check to make sure the voltage on the relay coil is actually switching. I think that relay selects UHF or 2M, so switch between those bands while watching the coil voltage on pin 8 of the relay switch from 12v to close to zero volts.
     
  8. N1EBC

    N1EBC Ham Member QRZ Page

    Sooooo i don't think I can access that pin unless I pull the board and flip it over . How is tat going to be on the final with no actual heatsink?

    If you have an alternative way to check it I'm all ears.

    Thanks
    Jason
    N1EBC
     
  9. KA9JLM

    KA9JLM Ham Member QRZ Page

    Can you get to the 22 Ohm resistor that is in series with the relay coil ?
     
  10. N1EBC

    N1EBC Ham Member QRZ Page

    That would be a negative as they are on the bottom side of the board.
    jason
    N1EBC
     

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