FT-991A 'HI SWR' when using ATU in 40m and lower bands

Discussion in 'Radio Circuits, Repair & Performance' started by PY2RAF, May 9, 2020.

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  1. SP3CET

    SP3CET Ham Member QRZ Page

    It's nice to read the opinions that this solution works, for me it appeared on 80m, I will check this solution too.
     
  2. PE1OUW

    PE1OUW Ham Member QRZ Page

    I had to send my FT-991A to the dealer for repair of - what I suspected - the final stage. I was trying to get my Endfed half wave working for the JS8 frequency on 80m, 3578 kHz. The internal tuner was engaged and after some seconds it switched off, assuming it would've found a match. In TX the SWR bar went full scale. So I repeated the sequence and the result was the same. Then I started to smell the odor of something we all hate - burning/smoking electronics. Switched off the rig and e-mailed the dealer. Long story short it appeared that some coils (and maybe even some capacitors - I forgot about that detail) in the final stage completely burned out. I haven't read about that possibility so far, but I find it rather disturbing this might happen as well.

    I hope the issue is now solved forever, but I will have a look at the internal AT anyway and remove lacquer if present. I also own an LDG Z100Plus matching unit which I will put in line asap, just to be sure it's not because of a matching issue problems will re-occur.

    Will keep you folks posted.

    Ramon, PE1OUW
     
    Last edited: Nov 5, 2021
  3. Z33ASB

    Z33ASB Ham Member QRZ Page

    Mine FT-991A is only 6 months old. From yesterday evening i have noticed this problem on 40m band, not so big but appears when radio was fully cold. The SWR, even it is tuned, was going more than 3 to 5 :(. I knew this problem before buying the radio but i though it can not happen to my new radio.
    When radio worms up everything was OK again. The problem reappears this morning again on cold radio, so I could not stand it any more :)
    -----
    Solved the problem with the standard procedure for repairing of Poor Grounding in FT-991A Tuner Unit.
    Here is the full info by PY2RAF that i have used:
    https://www.qsl.net/vu2msy/homebrew/FT-991A-Tuner-Issue-how-to-fix.pdf
     
  4. KN4YLL

    KN4YLL Platinum Subscriber Platinum Subscriber QRZ Page

    I have been doing some work on the 40m band, FT8. Never had a High SWR reading, until this evening. My SWR with analyzer is 1.27. Now when on freq 7.072600 with the radio and no tuner swr is at just at 1.5. However when the tuner shows on- the Hi SWR starts flashing. This is the first time I have noticed this. I guess I will try the cleaning the grounding pad...
     

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