Interested in a Powered LEMO Adapter?

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Rich
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Re: Interested in a Powered LEMO Adapter?

Post by Rich »

A caveat regarding Lightspeed Zulu 3 w/LEMO:

This model headset has no battery compartment. So use of this headset with any aircraft that does not supply panel power means that it's a passive headset and BT is unavailable.
2002 DA40-180: MT, PowerFlow, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal., Surefly, Flightstream 210, Orion 600 LED, XeVision, Aspen E5
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Rich
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Re: Interested in a Powered LEMO Adapter?

Post by Rich »

I did some digging (based on factory-installation wiring diagrams) and found 2 cases where this adapter won't work properly, if at all. I don't know how many of these might be out there.

- DA20's with PMA6000 audio panel.
- DA40's with KMA28 audio panel

All Diamond installations with any of the Garmin audio panels show wiring consistent with this adapter. But if subsequently a different audio panel was installed, there may or may not be a problem, depending on whether the factory wiring to the jacks was modified.
2002 DA40-180: MT, PowerFlow, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal., Surefly, Flightstream 210, Orion 600 LED, XeVision, Aspen E5
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waynemcc999
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Re: Interested in a Powered LEMO Adapter?

Post by waynemcc999 »

Steve was just in contact with Lightspeed (csupport@lightspeedaviation.com). They quote US$150 for the service to convert a Zulu 3 dual plug to a LEMO plug and indicated a turnaround of ~5 days once the headset is received by them.
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Rich
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Re: Interested in a Powered LEMO Adapter?

Post by Rich »

I was flying some practice approaches today with an acquaintance as safety pilot. I brought up my most exceptional invention based on the unique characteristics of Diamond dual-plug wiring. It turns out that he once worked for Mountain High, which markets an oxygen mask with built-in microphone. That powered tip caused them problems. We didn’t discuss further how it was resolved, but I wonder how the LEMO scenario interplays with such products.
2002 DA40-180: MT, PowerFlow, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal., Surefly, Flightstream 210, Orion 600 LED, XeVision, Aspen E5
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CFIDave
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Re: Interested in a Powered LEMO Adapter?

Post by CFIDave »

Here's a problem scenario that unfortunately played out in our DA62 this week:

In flight, one of our battery-powered dual-plug headsets apparently shorted out a powered Microphone Tip connector (something only found in Diamonds) to ground.

This caused a loud 'Pop" noise through everyone's headsets, which immediately killed power to all the LEMO-powered headsets!!! At that point the pilot and co-pilot with LEMO headsets (LEMO Lightspeed Zulu 3s without batteries) were left with only passive noise reduction. No panel circuit breakers popped. With loss of active noise reduction, I had to crank up the radio volume to clearly hear ATC during an IFR flight.

After reviewing the aircraft electrical schematics, it's pretty clear that shorting of the Microphone tip connection to ground blew out a 10W 100 ohm resistor in the panel that supplies 28VDC (from the audio circuit breaker) to *all* of the headset jacks -- powered LEMO plugs, as well as all Microphone Tip connectors on the dual-plug jacks.

On aircraft like the DA62 that comes equipped standard with powered LEMO and dual-plug jacks for all 7 seating positions, there's no need for Diamond to power dual-plug Microphone Tip connectors -- it's just asking for this kind of trouble.
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Rich
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Re: Interested in a Powered LEMO Adapter?

Post by Rich »

Dave, what kind of DP headset was it that shorted the circuit? I must say, in 20 years of having various headsets plugged in, my resistor is still intact. (On a related note, I wonder where that sucker might be? :scratch: )

The LS has no provision for battery, but the A20 does. I have decided to use the A20 for my seat due to other possible scenarios of loss of power (Electrical system failure, use of essential bus). So that I would retain ANR and BT. All seats are provided with LEMO headsets - two of which are lightspeeds.

For those with hard-mounted LEMO, perhaps consider dead-heading the dual plugs and provide reverse-LEMO adapters for DP headsets.
2002 DA40-180: MT, PowerFlow, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal., Surefly, Flightstream 210, Orion 600 LED, XeVision, Aspen E5
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Re: Interested in a Powered LEMO Adapter?

Post by CFIDave »

Rich wrote: Tue May 24, 2022 3:07 pm Dave, what kind of DP headset was it that shorted the circuit
It was a dual-plug battery-powered Bose A20 that I later discovered was worn by a passenger "backwards," reversing the left and right ear cups so that the mic boom was on the incorrect side and had to be rotated severely in the wrong direction, perhaps damaging the headset's mic internal wiring. Before all headset power blew out, I noticed that something might be wrong because whenever that passenger spoke, there was a faint "popping" noise that we all heard in the intercom.

Later, when I tried on that headset and reversed the A20's mic boom back to its normal position, the headset functioned perfectly. :scratch:

I think the takeaway from this is to avoid turning the A20 mic boom the wrong way when used on a Diamond with 28VDC powered microphone Tip jacks.
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Rich
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Re: Interested in a Powered LEMO Adapter?

Post by Rich »

A 100Ω, 10W resistor at 28 V should be able to handle a dead short without overload.

P=V**2/R = 28**2/100 = 7.84 W
2002 DA40-180: MT, PowerFlow, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal., Surefly, Flightstream 210, Orion 600 LED, XeVision, Aspen E5
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CFIDave
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Re: Interested in a Powered LEMO Adapter?

Post by CFIDave »

Rich wrote: Tue May 24, 2022 3:49 pm A 100Ω, 10W resistor at 28 V should be able to handle a dead short without overload.

P=V**2/R = 28**2/100 = 7.84 W
That's funny; I did exactly the same calculation last night (my EE degree was good for something. :) )

That's close enough to 10 watts that the resistor might still have blown, considering that 2 LEMO headsets were also drawing power thru the same resistor at the same time. I can't account for the loss of LEMO headset ANR power any other way, since the GMA 1360 audio system still works perfectly, and the panel's 5 amp Audio circuit breaker (through which the resistor and audio panel both draw power) never tripped.

We should be able to confirm what happened as soon as I can figure out where the resistor is hidden.
N62DV DA62 62.056
N42DA DA42-VI 42.N117 (sold)
N811ET DA40 XLS 40.874 (sold)
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Rich
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Re: Interested in a Powered LEMO Adapter?

Post by Rich »

CFIDave wrote: Tue May 24, 2022 4:11 pm That's close enough to 10 watts that the resistor might still have blown, considering that 2 LEMO headsets were also drawing power thru the same resistor at the same time.
That would be irrelevant, as there's no way 28.3V would push any more than 283 mA across 100 Ω. Of course the resistor could be out of spec.

One other possibility is a short in the mic jack. If a nut holding any of these jacks gets a bit loose the contact arms can move around and short against one another when a plug is inserted. I had this happen many years ago and it caused a nonstop squealing in the headsets when a plug was inserted into it. I do not recall whether it was a mic or audio jack. But careful tightening of the nut cured it for all time. You might check into this possibility before tearing into the panel.

I just thought I'd throw out a side point. I have an A20 and supposedly the mic arm travel is limited to 160 total degrees before hitting some resistance. Strangely, I find that the arm can be swiveled without resistance far more than that if it is rotated over the top. It rotates enough that one could use the headset backwards.
2002 DA40-180: MT, PowerFlow, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal., Surefly, Flightstream 210, Orion 600 LED, XeVision, Aspen E5
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