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Help with (partially) frozen GMA 340


y2kiah

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I took possession of my newly purchased 201, and within a few minutes of operating the avionics on battery power after the pre-buy inspection was done, the audio panel started exhibiting strange unresponsive behavior. The panel operated fine during my test flight with the previous owner, and he never had any issues with it.

I would press a button to monitor another radio and nothing happened. Some buttons worked while others didn't, but it appeared to be deteriorating quickly. At some point I switched it to com/mic 3 and the panel just outright froze, absolutely no button presses would respond except for the lamp test. Multiple attempts to cycle the power on the unit, and no change to the panel state, no responsiveness restored. Audio is flowing through the panel just fine throughout. I then ran up the engine to try the panel under alternator power, in case low voltage was the issue (12.0-12.2V on the battery at all times, everything else worked fine), and that actually restored some functionality and allowed me to switch to COM/MIC 2 (the SL-30 radio). I still cannot switch to COM1 which is the IFD440, and cannot deselect monitoring on COM1. Also the MKR mute cannot be deselected.

So in short it's still in a partially frozen state even under alternator power.

The unit is loose in the rack and wobbles easily. My next step will be to remove the hood and check for loose wiring.

Has anyone had similar issues with their unit or a similar one, and/or what would you recommend we look at?

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Your voltage is too low, especially if the engine is running.

I don't know what battery you're using, but I used a Concord 35AXC on my C and the manual HERE has the published values you should be using. The POH usually does as well.

Page 12 for the regulator settings and page 13 for the open circuit voltage (engine off) values.

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Loose in the rack doesn’t sound right or helpful...

See if that can be tightened with the screw/cam that typically holds avionics in place...

If you pull the device out... cleaning contacts is always helpful... get a can of contact cleaner...

 

Modern avionics have a voltage operating range... you can look that up easily... 12v should be well above the bottom of the range...
 

If your battery is low... hitting the starter should set off alarms for low voltage really easily...  this is a good reason for not having the avionics powered up until the engine start is over...

An idling engine typically doesn’t generate much voltage at low rpm....  if you have a generator... it won’t generate any voltage until over 1600 rpm or so...

 

PP thoughts only, not an avionics tech....

Best regards,

-a-

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thanks everyone, I'm going to try some more troubleshooting and look for a maintenance manual on this unit. I only have a pilot guide which is no help. ... also a good excuse for an upgrade to a Bluetooth unit.

-Jeff

Edited by y2kiah
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10 hours ago, chriscalandro said:

I’ll pm you. I have some experience with these. 

You don't have to announce that you'll PM him, you can just do it.

But if you did that, you couldn't show that you have information that you're not willing to share with the whole group.  Pretty childish, but typical of your behavior over the past few weeks after you got your feelings hurt by people trying to help you.

You've shown that you have absolutely nothing worthwhile to contribute here.  So in 7 years, you are now the first- and only- person I've ever blocked on MooneySpace.  Please do the same for me.

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The GMA340 typically has some side to side movement. 12VDC is plenty and won’t cause this. Try pushing the buttons slightly harder. I have seen this more than once on a 340. If it works when you push harder then the issue is in the unit. A re rack is a good start if what I mentioned above doesn’t work.


Sent from my iPhone using Tapatalk

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