GMA 240 died

Folks/brain trust,

I have a Garmin GMA 240 in my panel, not flying yet.

Last weekend I had everything powered up, (everything has been working fine together) and suddenly, without touching a thing, there was a small click from my audio panel and it went dark. Dead, nothing, nada. Checked the panel fuse and insured I have power to the pins. Problem is definetly internal.

So I had 2 headsets plugged into jacks that were wired to a disconnect switch for using monural headsets, which these were. Thought I had the disconnects switched to the "Mono" mode, but i guess I don't know for sure.

The manual says this can cause the "internal power supply fuse" to trip.

Does anyone know anything about this fuse? Can I replace it myself? Is there some other "reset" method I haven't spotted?

Hate to send it in and spend money.

Thanks in advance for your help.

Hello Jesse,

Call the number below and you will reach the experimental customer service group. They will take care of you and get your audio going again.

Thanks,
Steve

Yep. The 240 IMHO has a design defect, if it is wired for stereo and you plug in a mono headset it can blow the internal fuses. This is poor design, modern electronics are "short circuit proof". Other brands don't have this problem, nor does my home-built audio panel.

I won't be surprised if Garmin tells you that if you open it up you will void the warrantee. Only you can decide what to do.

GMA 240 cheap fix

Jesse,
Good news for you on this topic. Today my GMA 240 died for the second time. This time it was after an inadvertant switching of the stereo/mono switch on our headsets. It still worked in the fail-safe mode which let me transmit and receive on the primary comm radio even though there was no ICS and the entire unit wouldn't power up. After paying $250 to get this internal fuse fixed the first time my Dad and I decided to seek some help at the local Radio Shack before paying that kind of money again. The "Radio Shack guy" spotted the 1 amp fuse right off the bat. He tested it and it had failed. So he wired in a replaceable 1 amp fuse (pictured below) should this ever happen again. We powered it up and it worked like a charm. It cost us about $6.

Another option now that everyone knows where this fuse is located would be to replace it with the original fuse specification:

Click for link to where to buy and specs:


A person crafty in the art of reading specs most likely could find a self reseting poly fuse that would also work in this application.

Obviously any of this will void the warranty so do this at your own risk.

Wow

Thanks guys for the information. Hadn't called or sent the unit in yet so I think i'll head in the fuse replacement direction myself! I have a hard time paying $250 to fix a fuse in an $800 audio board. I'll let ya'all know.

Success!

Thanks to ApacheJoe for the fix you posted!

I tested the same fuse, found it blown and used the same repair you did.

I did indeed find that both of my mono/stereo headset switches were in the stereo position and I had mono headsets plugged in. Bad flaw in this piece of equipment.

I used an inline fuse holder I had on hand. I reduced the wiring size so I would not have the mass of the large wire to heat up when soldering to the on board fuse. Certainly don't want to put any more heat than necessary on the circuit board.

I also stuck a small piece of brillow pad in there to keep the fuse holder from bouncing around. The brillow pad will also allow air to move so the components on the circuit board can breath.

In the end, I know that I can simply remove the unit and replace the fuse easily in case I forget a switch position.........This just aint right.




Had to use a fine point on the soldering iron and used as little heat as possible. First tin the wire, second tin the fuse then join. Get the heat off.



Happy camper!



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340 too?

I was going to pick up a 240, but after reading the issues with it, I'll probably look at something else.

Does the 340 have the same issue?

Cheers,

Don

Don Patrick said:

I was going to pick up a 240, but after reading the issues with it, I'll probably look at something else.

Does the 340 have the same issue?

Cheers,

Don

Click to expand...

I had a PS Engineering PMA 8000B audio panel. An excellent panel, and no problem with mono/stereo.

PS Engineering AUdio Panels

Don Patrick said:

I was going to pick up a 240, but after reading the issues with it, I'll probably look at something else.

Does the 340 have the same issue?

Cheers,

Don

Click to expand...

Don, none of our audio panels have this problem. This is something we solved in 1992.

May I suggest the PMA5000EX?

Mark Scheuer
PS Engineering, Inc.

Confusion...

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

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.

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.

Airzen said:

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

Click to expand...

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

Airzen said:

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

Click to expand...

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.

g3xpert said:

,,,,,,,,,
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.

Click to expand...

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.

Thank you Steve!

Thank you Steve!

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

Ashish

Kudos Garmin

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

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.

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.

Good advice Ray. DigiKey has the small fuses and with a steady hand on the soldering iron, I think I can replace it. At least I am flying for the moment and I'll take your advice and see if I can fix this in a better manner.

Thanks!!

BTW, I've had just great response from Steve at Garmin regarding this issue. The newer GMA240s have a 4A internal fuse and a 1A recommended external fuse. So I have some 4A fuses coming from DigiKey and I'm going to carefully attempt to replace my inline fuse holder with the correct fuse on the board. But after some further testing this whole issue seems to be related to pluging in my iPhone to an external music jack. I'll have to do some further experimenting to find out just what is going on here.

Doug,

It's not that hard just take your time. Use some tweezers to hold the part. Tack down one side, then solder the other side. Make sure the solder reflows well but don't keep the heat on too long or it will heat up the whole part and then the tacked on side will reflow. Once the one side is soldered then go back over to the tacked down side and complete that side. Not much solder is required and a little tiny bit of flux can help. Digi-Key and Mouser sell flux pens that are helpful for this type of work. Most solder has flux in the core. The smaller the solder size usually the less flux and more of a need for additional flux. Also the flux burns off of the soldering iron tip so you need to wipe off the old solder a apply a little new and the quickly do your work. You can use a damp sponge to wipe off the soldering iron tip. Otherwise you need to apply the solder and the soldering iron to the part at the same time so that you get a good solder joint.

Once you have completed the soldering clean off any remaking flux with some alcohol and a qtip. If you are using leaded solder the joints should be shiny when you are done. If you are using lead-free solder good joints sometimes have a more matte finish but the solder should still still create a fillet between the part body and the surface mount pad.

Thanks Ray for the great tips. I'll let you know how it comes out.

Installed the 4A fuse today following your instructions Ray. Mission accomplished and everything works fine. Thanks Ray and Steve at Garmin! Saved me $225!