ICOM 756 pro II problem?

Discussion in 'Radio Circuits, Repair & Performance' started by CO8HF, Jan 20, 2021.

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  1. CO8HF

    CO8HF Ham Member QRZ Page

    Direct antenna without internal ATU on, it is seen that it does not indicate output power either
     

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  2. CO8HF

    CO8HF Ham Member QRZ Page

    And here is what the external SWR meter indicates, as seen, it says that the SWR goes down. The antenna is homemade ZS6BKW
     

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  3. CO8HF

    CO8HF Ham Member QRZ Page

    Look at the external SWR meter
     

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  4. VE1IC

    VE1IC Ham Member QRZ Page

    for starters, check the two diodes D1 and D2 on the CTRL board. They supply the swr voltage to the tuner and the meter.
     
  5. W1NB

    W1NB XML Subscriber QRZ Page

    What happens when you depress the PO Meter button, the second from the top?

    The internal SWR meter does appear to read differently than the external meter. It looks like the internal reads 3:1 when the tuner is off, while the external reads 1.5:1.
     
    Last edited: Jan 22, 2021
  6. CO8HF

    CO8HF Ham Member QRZ Page

    Exactly, the internal meter reads differently from the external meter, different readings, for the same antenna, and we do not see any indication of power output on the internal meter and it can be seen on the external meter
     
  7. W1NB

    W1NB XML Subscriber QRZ Page

    The SWR bridge contains two diodes, one to detect forward power and one to detect reflected power. I suspect the forward diode has failed which has eliminated the forward power measurement for both the power output meter and the SWR comparison. SWR is based on a ratio of forward to reflected power so with no forward power measurement the ratio of reflected to forward is erred.
     
  8. CO8HF

    CO8HF Ham Member QRZ Page

    Greetings, the transceiver has started to work, for days the meter works correctly indicating the parameters well, what happened? I don't know. Maybe a greemly, HiHi Thanks for the advice you have given me
     

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