Yaesu FT 450D will not transmit on LSB or USB part of the time

Discussion in 'General Technical Questions and Answers' started by W9EMM, Mar 9, 2020.

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  1. W9EMM

    W9EMM Ham Member QRZ Page

    I have a Yaesu 450D from time to time 50% of the time it will not transmit on usb or lsb . it will draw amps as if it is transmitting but there is no output. If I switch modes to CW or AM there is an output. Nothing has changed in my little shack the antenna is in the attic no change there. I have changed microphones does not change anything.

  2. N5NXZ

    N5NXZ Ham Member QRZ Page

    Do you see power when you speak into the microphone during LSB or USB transmitting?
  3. W9EMM

    W9EMM Ham Member QRZ Page

    There in no power output when it is not working when is does work the power meter fluctuates as I talk. When it is not working nothing. The amp meter on the power supply fluctuates as I talk when it is working. When it is not working the amp meter will read a few amps when I key the mic. I also have an homebrew RF meter near the antenna there is no RF when there is no power shown on the power meter of the radio. If all of that makes since.
  4. K7TRF

    K7TRF Premium Subscriber QRZ Page

    What does it take to get it back to an operational state when it fails in SSB transmit mode? Does switching the mode switch to CW and then back to SSB fix things for a while? If so, have you tried jiggling the Mode switch without actually switching modes when it falls into its failure state? Similarly have you tried jiggling or slightly moving the Mic gain knob when SSB fails? How about jiggling the microphone connector? Does power cycling the rig temporarily fix things?

    Does SSB receive continue to work when it's in the SSB failure state?

    If SSB receive continues to operate normally even when the rig won't transmit in SSB mode then I'd suspect a bad connection at a switch or connector. If switching the mode switch temporarily fixes things then I'd suspect contact problems on that switch. Similarly an intermittent connection on the mic jack or the mic gain control could cause the kinds of problems you're seeing. It could also be a loose board interconnection so you might look inside the rig to see if all the connectors are seated tightly.

    What sort of test equipment do you have to do further troubleshooting? If basic functional tests don't offer more clues I'd probably inject an audio tone into the mic jack and trace the signal forward through the audio amps and balanced modulator with an oscilloscope or other measurement tool.
  5. K7WFM

    K7WFM Ham Member QRZ Page

    My FT-950 used to do weird things if I controlled the input DC power via the power supply switch. Never had a problem with it using the power ON/OFF button on the rig. Do you use the rig power switch or just turn the power supply on and off?
    W9EMM likes this.
  6. KP4SX

    KP4SX Premium Subscriber QRZ Page

    Is the voltage AT THE RIG ok?
  7. W9EMM

    W9EMM Ham Member QRZ Page

    I use the rigs switch I am going to try a factory reset and see if that helps.
    Thanks for the reply
    K7WFM likes this.
  8. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    That takes ten seconds.

    Let us know what happens.
  9. W9EMM

    W9EMM Ham Member QRZ Page

    I have used two microphones. I thought at first maybe an over heating problem when I transmit, but the same thing happens if the radio is just receiving and I decide to answer a CQ. Switching mode does not help when I switch back to SSB it still will not transmit. When it is working it will send RF to the antenna on all modes when I key the mic. When it is not working it will not send RF on SSB , But it will send RF to the antenna on other modes when I key the mic. To explain how I know RF is going to the antenna my antenna is in the attic I built a simple RF detector using an Arduino and a DRO. I don't have anything other than a multimeter I will check wiring and will most likely box it up and send the radio in.
  10. W9EMM

    W9EMM Ham Member QRZ Page

    Yes I checked that it is fine.

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