Need help troubleshooting Omni VI Plus

Discussion in 'Radio Circuits, Repair & Performance' started by K5DH, Sep 11, 2020.

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  1. KL7SG

    KL7SG Platinum Subscriber Platinum Subscriber QRZ Page

    K1 is probably not the cause of the problem. The reason is that K1 is open during recieve and recieve is normal.
    During transmit, K1 is closed allowing the transmit RF to reach the antenna connector.
  2. K5DH

    K5DH Ham Member QRZ Page

    Hi all,
    I'll make some more measurements when I have time. Working full time at my job all day, and working on some home remodeling chores in the evenings.
  3. N7EKU

    N7EKU Ham Member QRZ Page

    Stay safe and good luck on the chores :)
  4. K5DH

    K5DH Ham Member QRZ Page

    OK, guys. I was able to make a new set of measurements this evening. TX voltages are with 100 W of RF applied, and receiver disconnected at J17. I'm using a Fluke 87V DMM here. I know that the presence of RF could mess with the readings.

    Attached Files:

    Last edited: Sep 19, 2020
  5. K5DH

    K5DH Ham Member QRZ Page

    The more I think about this, the more I feel like my DMM is not giving me the right readings. I'm going to re-measure everything with my VTVM and see what those results look like.
  6. KL7SG

    KL7SG Platinum Subscriber Platinum Subscriber QRZ Page

    During transmit:
    If you can, measure the junction of R10 and D9.
    Also, the junction of R26 and the collector of Q2.
    Make sure you have a good circuit card ground for these measurements.
    Diode D6 seems to be forward biased and I am not sure why that would happen.
    Maybe Q2 is on. Check the voltage on the emiter of Q2 also.
    Last edited: Sep 19, 2020
    WN1MB and N7EKU like this.
  7. WR2E

    WR2E Ham Member QRZ Page

    I would double check that the polarity of the replaced diodes is correct and don't assume that the silkscreen on the board is correct.
    WN1MB and KL7SG like this.

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