GMA 240 died - Page 2

Airzen · #11 01-02-2013, 06:40 PM

This might be a dumb question. But I am confused so here goes..

I have a Lightspeed Zulu 2 headset, and it has options for to be used in a 'mono' mode as well as the 'stereo' mode. (This called DIP switch, and factory default is to have this in the 'mono' mode).

So if I plug in the Zulu headset with factory setting ('mono' mode), will the fuse in GMA 240 blow? How can I find out without damaging my 800$ unit!!!

Ashish

BobTurner · #12 01-02-2013, 07:03 PM

With the zulu in mono, put an ohmeter between the ring terminal and the ground terminal, on the plug. If it reads open circuit, or anything more than 300 ohms, it is safe to plug in. If it reads close to zero ohms, then you will blow the fuse in the 240, assuming the jack is wired for stereo.

The zulu is a pain to change, I leave it in stereo. I have a Radio Shack mono to stereo adaptor plug for use in mono only airplanes.

apachejoe · #13 01-02-2013, 07:06 PM

Airzen,
The fuse shouldn't blow, at least right away. This excerpt was taken from pg. 3-3 of the GMA-240 installation manual.

Stereo headsets are recommended if stereo jacks are installed. Alternatively, the installation should employ stereo jacks with a mono/stereo switch that disconnects the audio panel?s right channel output from the jack?s ring contact when in mono mode. If a monaural headset is used in a stereo jack, the audio panel?s right channel output is shorted to ground by the mono headset?s plug. This causes excess power supply current to be drawn. While this does not damage the unit?s output circuitry, prolonged periods (especially at high volume) may cause the internal power input fuse to open.

In my case the "prolonged period" lasted about 1 second. The other time the fuse blew was when we first testing the install in our basement. We were playing music through the comm panel and testing all the headsets when the fuse blew. The unit had never even flown but since we had it for longer than a year Garmin charged us $250 to fix it.

In my opinion you shouldn't be able to blow a fuse if you tried. With today's technology these things should be bullet proof. In any case, if it does cause the fuse to blow, the previously posted repair is easy.

Brantel · #14 01-02-2013, 08:23 PM

Quote:

Originally Posted by Airzen

This might be a dumb question. But I am confused so here goes..

I have a Lightspeed Zulu 2 headset, and it has options for to be used in a 'mono' mode as well as the 'stereo' mode. (This called DIP switch, and factory default is to have this in the 'mono' mode).

So if I plug in the Zulu headset with factory setting ('mono' mode), will the fuse in GMA 240 blow? How can I find out without damaging my 800$ unit!!!

Ashish

Set the Zulu to Stereo and be done with it. It will sound better and you won't damage your unit.

g3xpert · #15 01-03-2013, 06:17 AM

Quote:

Originally Posted by Airzen

This might be a dumb question. But I am confused so here goes..

I have a Lightspeed Zulu 2 headset, and it has options for to be used in a 'mono' mode as well as the 'stereo' mode. (This called DIP switch, and factory default is to have this in the 'mono' mode).

So if I plug in the Zulu headset with factory setting ('mono' mode), will the fuse in GMA 240 blow? How can I find out without damaging my 800$ unit!!!

Ashish

Hello Ashish,

This is not a dumb question at all. Let us make it very clear.

A stereo headset is safe to use with the GMA240 no matter how any switch is set!

The stereo/mono switch on the headset OR the optionally installed stereo/mono switch shown in the diagram below may be set to any position with a stereo headset and there is no risk of blowing the internal fuse.

The mono/stereo switch in your Zulu does not switch the ring to ground, it connects the ring and tip so a mono audio signal supplied to the tip can be heard in both channels on a stereo headset.

The design of the stereo phone jack used on each stereo headset provides isolation between the tip and ring and can never short either to the sleeve (ground) shown in this diagram.

As suggested in the installation manual and by others here, it is not typically easy to blow this fuse.

For example, I have a GMA240 running on a bench with XM music fed into Music Input 2 from a Garmin portable. The music volume on the portable is set to 3/4 scale (quite high). The Music 2 input is selected on the GMA240. The headphone jacks are wired for stereo and there is no mono/stereo switch in the jack circuit. I have a multimeter monitoring the input current (which is flowing through the internal 1 amp protection fuse).

With the music turned to a normal listening volume and a Zulu stereo headset plugged in, the current is 0.22 amps. If I turn the music volume up to an almost unbearable volume using the music volume knob on the GMA240, the currrent is still 0.22 amps.

Now, if I return the music volume to a normal listening level and put a grounding clip between the ring and sleeve to ground (short) the right audio output channel to simulate a mono headset jack being inserted, the current only increases slightly to 0.23 amps. Still no problem with ever blowing the 1 amp internal fuse.

Now, with the right output channel still shorted to ground, I increase the music volume (again using the music volume control on the GMA240) to that almost unbearable level, the current increases to 0.35 amps. Still no problem with ever blowing the 1 amp internal fuse.

Now, with everything still shorted, I remove the headsets to protect my ears and crank the music volume up to the point where I worry that my headset might be damaged, the current increases to roughly 0.60 amps maximum. Still lots of margin and no blown fuse after several seconds of operation at a level that I would never select.

With multiple headsets plugged in and shorting the right audio channel to ground, and the music volume turned up high, you could indeed reach a point where the 1 amp internal fuse is blown. The GMA340 has a 4 amp internal fuse to protect the power supply, and we are not sure one of those has ever blown.

The GMA240 installation manual requires that power be supplied to the GMA240 through a 1 amp external circuit breaker or fuse. One of the many options we are considering is simply increasing the size of the internal fuse from 1 amp to something large enough that it will never blow before the external 1 amp protection is tripped in the event that any headsets are improperly shorting the right audio channel to ground and a very high volume is being used.

In summary, with your stereo headsets, wire your phono jacks for stereo and don't worry about anything. Nothing you can do with switches can cause a problem.

Thanks,
Steve

P.S. If you experience a problem with your GMA240, please call us and let us work with you.

9GT · #16 01-03-2013, 11:09 AM

Quote:

Originally Posted by g3xpert

,,,,,,,,,
In summary, with your stereo headsets, wire your phono jacks for stereo and don't worry about anything. Nothing you can do with switches can cause a problem. Thanks,
Steve

P.S. If you experience a problem with your GMA240, please call us and let us work with you.

Thanks for this reply Steve. I have a GMA-240 on order with the rest of my avionics package and was just about to call SteinAir and have it swapped out for something else.

Airzen · #17 01-04-2013, 04:19 PM

Thank you Steve!

That was a great expnantion and puts my mind at ease!

Ashish

rivetshaver · #18 11-11-2013, 07:14 AM

My GMA 240 died during testing just before my first flight this September.
The co-pilots headset was unknowingly set in mono mode. MY son was helping me , all worked well with the pilots side and the intercom, but when he did a transmit test there was a squeal and the panel died, bummer. I borrowed a friends panel, it worked great. I contacted Garmin explained what happened and requested warranty service even thoug it was purchased 3 years ago during the panel build, I made my case based on posts in this thread. The Garming rep said no problem, all it cost me wa $8 for shipping.
Thanks Garmin
Gregory Targonski

dougweil · #19 07-27-2015, 08:17 PM

I see this is an "old" thread but I just went through a similar situation with my GMA 240. It is 4 years old with 395 trouble free hours. For no apparent reason today it quit (been using Bose X headsets all this time). I did have my iPhone audio output plugged into an external music jack (all of this wired by SteinAir). Since my box is out of warranty, Chris at Stein suggested looking at this thread. I removed the cover and yes, the internal fuse was blown. You can see I wired in an in-line 1 amp fuse as in previous posts and it seems to work fine. I had the 240 protected by a 5 amp external fuse. I may switch this to a 1 amp. Regardless if this blows again, I may have other issues somewhere.

rapid_ascent · #20 07-28-2015, 09:36 AM

I'm going to stick with Brian on this one. Buy the right replacement if you are going to replace it yourself. The original seems to be a surface mount part per Brian and surface mount pads can easily be lifted off if the PCB. Having a long wire attached to these pads especially a heavy gauge wire is just asking for trouble. I'm not saying that this can't be done but I would make sure you have the skill to do it properly and strain relieve the pads. Again I wouldn't do this.