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Thread: Sl40 install troubleshooting

  1. #1

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    Sl40 install troubleshooting

    I just bought a new Garmin sl-40 with prewired harness from Aircraft spruce. My avionics AME & I just put it in, & it isn't happy!

    We left speaker & intercom disconnected, and hooked up 1 headset. There's a lot of noise on the headset regardless of volume, frequency display flashes on & off, and pressing push-to-talk causes radio display to black out for several moments.

    Microphone ground (as labelled on the harness) shows 100 ohm impedance to radio/panel ground. Is this normal?

    Any suggestions? Anyone?

  2. #2
    www.SkupTech.com mike mcs repair's Avatar
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    1.sounds like bad ground or bad power/breaker

    2.ground looping?? is mic jack grounded to airframe

  3. #3

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    We disconnected the mic jack from the panel, problem didn't go away, but radio stopped "crashing" when push-to-talk was pressed.

    As for breaker power/ground problems: radio chassis to battery neg terminal impedance was 0. Power was connected to an older 5A breaker, I guess I could try wiring direct to the battery for testing.

    The plane's an hours drive away, so the more suggestions you give, the fewer trips I'll have to make.

  4. #4
    Steve Pierce's Avatar
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    I would call Spruce and tell them what it is doing. They have the wiring schematic and should be able to tell you exactly what the problem is and send you a replacement harness if that is the problem.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

  5. #5

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    Spruce bumped me to Garmin immediately. Garmin's very helpful.

  6. #6

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    The problem was traced to an old breaker in the panel + too thin wire connecting the Avionics Bus.

    I took it flying for the first time just recently. That automatic squelch works great, and what a relief it is to be understood!

  7. #7

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    Update..

    I *think* I just got the intercom feature to work. The Radio itself put on an outstanding performance in the last float season. It was loud, clear, and it appeared to have very good range. Unfortunately the headphone-out was badly mis-matched with the portable intercom I had hooked into it.

    So this spring's mission was to get the SL-40's built in intercom to work. I can honestly say it's almost as much work as getting the radio installed in the first place. The display has an "I" icon that appears when the intercom is functioning, and while my radio's audio output has mysteriously grown softer (even when only 1 headset is plugged in), the aural "echo" of the intercom sounds very clear.

    Getting the intercom to work was mostly about tuning the microphone squelch in the config menu. I found these settings had no effect on radio transmit, but leaving the squelch at 0 prevented the intercom from working. Higher numbers mean more sensitivity, and in ground tests a 60 is required for the intercom to clearly capture everything I'm saying.

    Other tips I got elsewhere were: (possibly) build an impedance matching circuit around the mic in and headset outputs on the radio, and play with the widely misunderstood sidetone level.

    Garmin was a great help with my radio last summer, this year they don't seem to be answering their mail. So long as they make great products, I suppose that isn't too bad.



    Another poster (who sounded like an electronics guy) was complaining about a poor impedance match between the headphone-out of the radio and the headset input.

  8. #8
    SC3CM's Avatar
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    The sidetone was the key to getting the SL30 dialed in. It's the same as the 40 but has nav available.
    One thing I noticed with the built in intercom, at least in my plane, is the headset used makes a tremendous difference in the audio settings used to get the same quality sound (internally at least, I've never been told it sounds poor from another plane).

    My David Clark enc head set does well, the Bose A20 though is now my favorite by far. The original Bose was completely worthless though. If someone in the back uses a mono headset (pos kids headset for example) I have to reset the side tone and intercom levels. If the back seat is using the Bose A20 for example, or the DC enc pair, nothing changes in the front.

    This isn't an answer to your question, but maybe some of my trouble will help you find a solution faster. The radio is very nice once you get it dialed in!

    Rene

  9. #9

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    I have had no trouble with the SL-40 except for those bone headed memory setups, but I use the PM 501 intercom. It has a knob for "door open or door closed" squelch. I think I have had mine for ten years or so.

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