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  #1  
Old 06-29-2020, 10:20 AM
Piper J3's Avatar
Piper J3 Piper J3 is offline
 
Join Date: Nov 2014
Location: Hinckley, Ohio
Posts: 2,010
Default Garmin SL-40 Comm Problem

Three flights ago I started noticing a popping sound in my headset - small popping sound just once in a while. Two flights ago the sound became more frequent and the received voice was getting harder to distinguish. Yesterday?s one-hour flight relinquished the radio pretty much useless. What I noticed was the Tx light on the radio face panel was flickering in conjunction with the popping sounds. I tried troubleshooting in the air as best I could; un-connecting / reconnecting headset plugs, isolate intercom, shut off intercom, test both PTT switches, etc. By chance I pushed on the face of the radio and the comm became solid again. Release pressure and popping again. So, once on the ground I pulled the radio and used electrical contact cleaner and then electrical silicone liquid lubricant on both the connector on the back of the radio and also the mating connector in the radio tray. Still have problem...

I took the faceplate off the radio, removed ribbon connector, removed three screws holding faceplate circuit board and reassembled unit. I won?t be able to try radio until tomorrow.

Any thoughts on how to troubleshoot or suggested avionics repair shop?
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Jim Stricker
EAA #499867
PPL/ASEL 1970 - Sport Pilot since 2007
80 hrs Flying Aeronca Chief 11AC N86203
1130 hrs Flying 46 Piper J-3 Cub N6841H
Bought Flying RV-12 #120058 Oct 2015 with 48TT - Hobbs now 602

LSRM-A Certificate 2016 for RV-12 N633CM
Special Thanks... EJ Trucks - USN Crew Chief A-4 Skyhawk
MJ Stricker (Father & CFI) - USAAF 1st Lt. Captain B-17H
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  #2  
Old 06-29-2020, 12:08 PM
Pdtofly Pdtofly is offline
 
Join Date: Jan 2012
Location: Reno, NV
Posts: 433
Default Repair, two options

Check you PM for options.

Brian
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  #3  
Old 07-01-2020, 12:28 AM
Piper J3's Avatar
Piper J3 Piper J3 is offline
 
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Update - I disassembled entire radio and reassembled. Nothing inside radio looks out of place. Radio acts solid when airplane powered in hanger but popping noise returns when engine started and vibration shakes radio. Again, If I push face plate with my finger the radio works perfect. So, I think problem is in connection to mounting tray. I took Allen wrench with me on test flight and tried tightening/loosening the cam lock in flight. I found it made a significant difference but couldn't find slide-in position that solved problem in its entirety.

Tomorrow I will investigate mounting tray connector...
__________________
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Jim Stricker
EAA #499867
PPL/ASEL 1970 - Sport Pilot since 2007
80 hrs Flying Aeronca Chief 11AC N86203
1130 hrs Flying 46 Piper J-3 Cub N6841H
Bought Flying RV-12 #120058 Oct 2015 with 48TT - Hobbs now 602

LSRM-A Certificate 2016 for RV-12 N633CM
Special Thanks... EJ Trucks - USN Crew Chief A-4 Skyhawk
MJ Stricker (Father & CFI) - USAAF 1st Lt. Captain B-17H
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  #4  
Old 07-01-2020, 04:54 AM
noelf noelf is offline
 
Join Date: Nov 2007
Location: Cary, N.C.
Posts: 1,210
Default

Have you visually verified that the radio fully seats in the tray? For the SL 40, the back of the faceplate must just touch the front of the mounting tray when fully seated. If it seats on the instrument panel first then that is not correct.

With the radio removed from the tray, look at the worm screw / locking finger. Turn the worm screw and watch the travel of the lock. There should be minimum free play with the worm screw, and the lock reeds to travel the full length...both for and aft. Sometimes the set screw in the locking collar comes loose and causes problems.

Do you have extra pins and sockets. If so, you can attach them to the ends of wood chop-sticks or wood skewers. Next, remove the radio from the tray and do a very careful visual inspection of each connector pin at the back of the tray. Are they all sticking out exactly the same distance?

Next, use your new pin tool and carefully use it to slide into each connector pin position. What you are looking for is a difference in the pressure that it takes to insert the pin and withdraw the pin from each position.

Do the same test for each pin on the back of the radio.

If you have some extra #20AWG wire, you can crimp this wire onto the pin/socket before you attach it to the wood chop-stick. This becomes a handy tool for chasing wires in the radio stack.
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  #5  
Old 07-01-2020, 01:39 PM
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Piper J3 Piper J3 is offline
 
Join Date: Nov 2014
Location: Hinckley, Ohio
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Update today ?

I removed the mini iPad at the top of the radio stack so I could look at the top of the Garmin SL40 tray. Back connector has screws tight. All female socket pins look to be seated correctly and at uniform depth in the connector.

I flew with the iPad removed and I could reach in and touch the top of the radio. I think there is a loose connection inside the radio. If I apply hand pressure down on the top of the radio the pop/click noises subside.

I brought the radio home and plan to disassemble again and visually inspect with magnification.
__________________
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Jim Stricker
EAA #499867
PPL/ASEL 1970 - Sport Pilot since 2007
80 hrs Flying Aeronca Chief 11AC N86203
1130 hrs Flying 46 Piper J-3 Cub N6841H
Bought Flying RV-12 #120058 Oct 2015 with 48TT - Hobbs now 602

LSRM-A Certificate 2016 for RV-12 N633CM
Special Thanks... EJ Trucks - USN Crew Chief A-4 Skyhawk
MJ Stricker (Father & CFI) - USAAF 1st Lt. Captain B-17H
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  #6  
Old 07-06-2020, 06:34 PM
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Piper J3 Piper J3 is offline
 
Join Date: Nov 2014
Location: Hinckley, Ohio
Posts: 2,010
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Update 7-6-20. I removed instrument bay cover to look at D-sub on back of Garmin radio tray and discovered the Coax connector was loose. The connector is held in place with two nuts and one had fallen off and the other was extremely loose. Nuts have a special pilot bore that centers and locates the Coax connector so radio engages properly. Couldn't find replacement nut so needed making my own. Now radio is operating hunky-dory...
__________________
-
Jim Stricker
EAA #499867
PPL/ASEL 1970 - Sport Pilot since 2007
80 hrs Flying Aeronca Chief 11AC N86203
1130 hrs Flying 46 Piper J-3 Cub N6841H
Bought Flying RV-12 #120058 Oct 2015 with 48TT - Hobbs now 602

LSRM-A Certificate 2016 for RV-12 N633CM
Special Thanks... EJ Trucks - USN Crew Chief A-4 Skyhawk
MJ Stricker (Father & CFI) - USAAF 1st Lt. Captain B-17H
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