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


    Just checking back on this to see if you’ve made any progress? Troubleshooting on modern radios can be challenging, especially when the circuit components you need to test are on the bottom side of the board. Below are a few suggestions. Apologies if I’m stating something you already know.

    1) Boards can usually be powered outside the chassis but you need to be very careful with interconnection cables, especially the ribbon cables. If you do this, keep the radio turned off until just before you are going to test and don’t leave it on for long. Heat will increase quickly on components that need sinking, like regulators and, especially, the audio output amp.

    2) A safer solution may be to remove the board and carefully solder a thin insulated wire at the test location, then replace the board and use the wire as your test location. This is really only practical for one or two tests. If you are stepping through multiple test points or stages it becomes annoyingly tedious.

    3) Another option is to remove the board and use your VOM to test continuity and components. If you know where the circuit is working and where it’s not, testing components that are logically associated with the circuit can be effective. For instance, test D1116, Q1127 and R1616, then test for continuity between components as shown in the schematic. If all tests good then it’s a pretty safe bet that if the relay is not switching, it’s probably bad. One note on testing Q1127, that transistor has integrated biasing resistors so you’ll need to check the transistor’s data sheet to determine the resistor values and factor those into your measurements.

    4) Final suggestion is to confirm the relay switching before you pull anything apart. You can often do this by carefully placing the blade of a screwdriver on the plastic cover of the relay and place your ear on the screwdriver handle, then key the mic. The screwdriver will help transmit the sound to your ear, making it much easier to here the relay click. If you hear the click then it’s receiving it’s switching voltage, indicating no issues with the circuitry and likely a bad relay contact. Of course, this method will only confirm that the relay is switching so if its coil is opened, or solenoid jammed, it won’t be very helpful.
    K7JEM likes this.
  2. N1EBC

    N1EBC Ham Member QRZ Page

    Actually i have had to put it aside for some other things. But heres a thought. i have a current limited power supply. How about not powering the radio but power the relay to check switching action? That way we find out whether the relay is actually working or not? And I don't have to worry about heatsinking certain items. Let me know what you think. If this will work i will check all 3 relays that way.
  3. W1NB

    W1NB XML Subscriber QRZ Page

    That will work for testing the relay but not the switching circuit. If you do this, make certain you observe polarity. Reversing it could cause more damage.
  4. N1EBC

    N1EBC Ham Member QRZ Page

    Ok first i have to put a vol pot in my ft-2900 so I can hear the 2m repeater again then i can can get back to this one.

    The whole deal with this stuff is i don't have much money and people give me broken stuff so if i want to be a ham I have to find a way to get it working. No real mentors locally that ive run into for electronics knowledge so i learn from others online and i appreciate all of your help.

  5. W1NB

    W1NB XML Subscriber QRZ Page

    I’m happy to help. BTW, why does your QRZ city info say Pace but shows your county as Alachua? Those two are barely in the same universe.
  6. N1EBC

    N1EBC Ham Member QRZ Page

    I have no idea its not something I think I can change. But alchua is the first county in FL alphabetically while Santa Rosa is near the end. Maybe it wasn't selected when account was made? That page I thought was automatically filled from FCC info though.

  7. W1NB

    W1NB XML Subscriber QRZ Page

    I think that’s correct. I believe it comes from the FCC license data. It just caught my eye. I spent a fair amount of time in Alachua and High Springs over a period of 15 years and I’d not heard of pace. I had to look it up.
  8. N1EBC

    N1EBC Ham Member QRZ Page

    All fixed nowOpen your database
    For example: https://www.qrz.com/edit/N1EBC
    Click the top menu "Update the basic callsign data (name, address, email, etc.)"
    Set "County" as you like
    Click "Save" to save the changes

    W1NB likes this.
  9. N1EBC

    N1EBC Ham Member QRZ Page

    Finally got some relays on hand now. will pull pcboard this weekend to test relays.

    KA9JLM likes this.
  10. N1EBC

    N1EBC Ham Member QRZ Page

    Ok RL101 applied 12v onside switches the other side does not. Popped plastic off the side that doesn't switch is discolored. Popped in new relay closed it back up. 50 watts output on 2m into a dummy load. Next test is the local repeater.

    Thanks for all the help
    KA9JLM, AC1HH and W1NB like this.

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