FT-991a Audio Gain does not reduce to zero

Discussion in 'General Technical Questions and Answers' started by M1PWT, Feb 24, 2021.

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  1. M1PWT

    M1PWT Ham Member QRZ Page

    Hi All,

    Audio gain knob on the front panel doesn't completely reduce the volume to zero.

    It works fine in normal use, I can balance the level of audio easily. But when I want to leave the radio in RX but turn volume down to zero to concentrate on something else then I can still hear it. Which is distracting.

    I have the latest firmware installed, The problem is both with internal loudspeaker and headphones. I can hear the RX audio as well as button press beeps.

    Looking inside at the front panel circuit board, the potentiometer appears to be cleanly flow-soldered on. I was hoping/expecting a bad solder joint here but it looks and measures fine.

    I've read through the technical supplement to see if I can find an alignment for this but can't see it there.

    Anyone able to help?



    PS Let me know if this is the wrong forum!
  2. M0KKM

    M0KKM XML Subscriber QRZ Page

    Yep, same here FT-991A, I guess its a "feature" that Yaesu may fix in a software update...
  3. W9WQA

    W9WQA Ham Member QRZ Page

    some "pots" just dont go to zero. yrs ago some would go past zero...

    if, its not a digital problem...
  4. G8FXC

    G8FXC XML Subscriber QRZ Page

    Mine goes close enough to zero that I've never noticed any residual output. Next time I'm in the shack, I will pay careful attention. I have had another Yaesu at some time in the past that definitely did not go to zero - its minimum volume level was surprisingly high. I don't remember the model - possibly an FT-847...

  5. PA5COR

    PA5COR Ham Member QRZ Page

    Thee FT847 had that indeed, i changed thatinternally.
    My FT991A does not have the problem here ( Made in March this year) it even has a 10 degree turn from off to the first audible sound with headphone on, i have the latest software in the transceiver.
  6. KA9JLM

    KA9JLM Ham Member QRZ Page

    I don't know how many times I have heard a operator transmitting, But the volume is down so they never hear any reply.

    Yes it is a Operator Error "feature" that should not be altered. But a resistor could "Fix" it.

    The ON/OFF button Mutes the radio completely, So it does not bother you. :)
  7. W9WQA

    W9WQA Ham Member QRZ Page

    pot goes below zero on the resistor element
  8. M1PWT

    M1PWT Ham Member QRZ Page

    Listening on headphones and moving the pot, the volume seems to increase immediately off the end stop. And the circuit diagram shows the two ends of the pot connected at +3V and GND. So I'd say that it doesn't seem to be a problem in the analogue domain. Or a problem I could fix with a modification (especially given the density of components on the expensive looking PCB).

    The signal level from the pot wiper goes to an input on an analog mux/demux chip and then direct to an input pin on the main control board FPGA where I assume it is digitised.

    Interesting that PA5COR reports the opposite to my problem.

    For context: Mostly I work digital modes WSPR, FT8, APRS etc. I don't want to use squelch and risk cutting the preamble off incoming data. Digital modes are really good fun but they sound terrible.
  9. W9WQA

    W9WQA Ham Member QRZ Page

    i was thinking of that but had no details !!

    some "pots" just dont go to zero. yrs ago some would go past zero...

    if, its not a digital problem..."...!!
    M1PWT likes this.
  10. M1PWT

    M1PWT Ham Member QRZ Page

    W9WQA: You are dead right about those old pots going off the end. I remember them very well.

    It's quite unusual to find a pot in a circuit at all these days. I was really expecting rotary encoders all round when I started looking.

    Maybe I should be posting about this where Yaesu might read it? Anyone know a likely forum for Yaesu bug reports etc?

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