Collins VHF-251 question

Discussion in 'Avionics and Upgrades' started by RickC, May 21, 2020.

  1. RickC

    RickC Filing Flight Plan

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    I have one of these and suddenly the sidetone has gotten very loud. I had pulled it to test another radio in the tray so it's possible that something got changed while I had it out, but I didn't intentionally turn any knobs or anything. Anyone know how to adjust sidetone on one of these?

    Thanks
     
  2. flyingron

    flyingron Touchdown! Greaser!

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  3. RickC

    RickC Filing Flight Plan

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    thanks, I'll see if I can find it in there
     
  4. Nathan Miller

    Nathan Miller Pre-takeoff checklist

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    I have the VHF-250. I understand the only difference is the display.

    I bought the plane in November. I'll show you what I started with-

    IMG_4317.jpg

    Side tone was good when I bought it. I was up against the ADS-B deadline and had a Garmin dealer remove the xponder and ADF and put in a GNX 375 GPS/Transponder. Afterwards, the side tone was non existent. It wasn't worth taking it back and having the dealer futz with since we were planning on replacing the audio panel and radios eventually.

    Late Feb/Early March, my partners and I start to move forward with the radio and audio panel upgrades. Given concerns about a hit to income with Covid-19 hysteria ramping up, my partners and I decided to pare back our install to just the audio panel and com radio and self-install under the supervision of our IA. Our #2 com had a weak rx and tx and up until this point, had been relegated to ATIS/AWOS duty. But, we were planning (hoping, more like it) to reuse the existing antenna and cable. So, I swapped the #1 and #2 coms to see if it was the radio or wiring/antenna. I telephoned our field's tower, told them I would like to do a coms check and asked if that would be okay. Traffic was slow and they said "No problem, just hit us up on clearance delivery, since no one uses it anyway :lol:

    Anyway, long story short, lo and behold, both radios functioned flawlessly - strong TX and clear RX on both radios. And sidetone came back! I guess just unseating and reseating the pins did the trick. If this doesn't work out for you, there is a potentiometer for side tone (bottom of unit). Both courses of action would require a logbook entry and since it's a tray mounted avionics (and not a transponder), you are able to sign it off as PM as the pilot.

    sidetone.jpg

    Click on the thumbnails for the full version, of course :)
     
  5. Nathan Miller

    Nathan Miller Pre-takeoff checklist

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    Just reread your original post - our side tones went in different directions :eek: but it still may be worth reseating the unit prior to futzing with the sidetone potentiometer. fwiw.
     
  6. FORANE

    FORANE Pattern Altitude

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    I had a VHF-251 in my Lancair when I bought it. Removed it for "upgrade" because I needed panel space in the rack to install a 430. Went through a SL-40, Icom A-210, GTR-200, and 430 traded out for 430w. The VHF-251 was a better radio than any of the others that have been in the plane. It's a boat anchor but it performed far better than anything else I have tried.