ft-8900 no 2m TX

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

ad: L-HROutlet
ad: l-rl
ad: L-Geochron
ad: MessiPaoloni-1
ad: abrind-2
ad: HRDLLC-2
ad: Left-2
ad: L-MFJ
ad: Left-3
  1. N1EBC

    N1EBC Ham Member QRZ Page

    I have a FT-8900 radio everything works fine except the 2m tx.

    anyone willing to walk with me or walk me through the repair?
    attached service manual and manual.
    This evening I will be setting everything up for working on it. I have scope, dummy load, and can probably come up with whatever else might be needed.


    Thanks
    Jason
    N1EBC
     

    Attached Files:

  2. N1VAU

    N1VAU XML Subscriber QRZ Page

    First thing, MASTER RESET, then test to see if it works again.
     
  3. N1EBC

    N1EBC Ham Member QRZ Page

    Just did that. No change. Still no tx on 2m other bands ok
    Thanks
    Jason
    N1EBC
     
  4. W1NB

    W1NB XML Subscriber QRZ Page

    Jason,

    I would start by checking the VHF oscillator Q1111 output. Depending on what you find you can go forward or backward from there.

    Scott, W1NB


    3C6746A0-F997-4F10-B5F6-66D20532BC01.jpeg
     
  5. K7JEM

    K7JEM Ham Member QRZ Page

    If you listen on a nearby handheld radio, tuned to 146.52, or some simplex frequency, can you hear yourself transmitting? Trying to determine if your radio is working up to the final amplifier, or making sure that the lower level stages are working.
     
  6. N1EBC

    N1EBC Ham Member QRZ Page

    Yes it works both ways TX/RX

    Jason
    N1EBC
     
  7. N1EBC

    N1EBC Ham Member QRZ Page

    Just wanted to be sure that this also answers what you ask
    If you listen on a nearby handheld radio, tuned to 146.52, or some simplex frequency, can you hear yourself transmitting? Trying to determine if your radio is working up to the final amplifier, or making sure that the lower level stages are working.

    Thanks
    Jason
    N1EBC
     
  8. W1NB

    W1NB XML Subscriber QRZ Page

    Not necessarily. The buffer stage, pre driver stage, driver stage or final stage could be bad but still generate enough RF to be heard on a receiver. I suggested starting at the buffer because it’s the first stage after the oscillator and is likely on a different voltage rail from the PA section.

    Do you have a solder/desolder station to replace SMD devices?
     
  9. N1EBC

    N1EBC Ham Member QRZ Page

    Ok Fair enough.. Haven't had time to lay stuff out. I'll get everything setup for probing. I have a scope, solder iron, desolder gun , and a hot air gun(which I am super hesitant to use).

    After work tomorrow I'll probe the oscillator . On this radio we know the final works as 70cm, 10m, 6m all put out wattage on the watt meter. So i guess while I'm probing I will also check the input of the final then the output. And get back to you. Reason why not tonight is I try not to do too much technical this late as more mistakes happen when I'm tired. But I'll have everything ready for after work tomorrow.

    Thanks,
    Jason
    N1EBC
     
  10. N1EBC

    N1EBC Ham Member QRZ Page

    Ok I got it setup and couldn't wait. So I have a signal at q1111 and I also have a large signal on the output of the final.
    So I'm ready to move forward after work tomorrow.
    Thanks for your time.
    nosaj
    N1EBC
    On the image red arrows are where I got signal at.
     

    Attached Files:

    Last edited: Oct 13, 2021

Share This Page