Major Audio Problem

I have had excellent service from my Skyview Touch/Flightcom 403/Garmin SL40 system for the past 3 1/2 years and 270 hours. Now I am experiencing several issues and the situation seems to be deteriorating. First, I am hearing a buzz in the intercom that is sympathetic with engine RPM, and seems to get louder at low RPM. I can stop the hum if I turn off the SL40. Second, when I first turn on the avionics the SL40 will transmit just fine, but after it warms up a bit, I get a very loud hum when I transmit. These conditions are making the comm system almost unusable. My guess is that the SL40 is going south. If that is tie case, where do I go from here? Thanks for your thoughts, and I am sure that I am not the first to experience these conditions, but I have been unsuccessful with my searches on the subject...........Tom

Did you try it with the alternator off? Lots of regulator issues on the 12.

pilot2512 said:

Did you try it with the alternator off? Lots of regulator issues on the 12.

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Everything was off, including the battery charger. All I have to do is turn on the master, and have the avionics master, and comm radio on. No engine running, so no charging circuit is active at the time of the test. The first press of the xmit key is quiet, then if I press the exmit key again after about a minute or so, I get this very loud and annoying back feed hum. ...Tom

I just got off of the phone with Garmin. They have a $550 bench charge for fixing SL40s. Wow! Maybe it is time to move on. The Dynon VHS com unit is $1300. Has anyone made the swap from an SL40 to the Dynon com? It would be interesting to get an idea about the challenge. I plan to take my SL40 to a Garmin shop for a bench test to verify that it is bad. However the best test would be to swap out my SL40 with another unit. Does anyone have one on the shelf that they would consider loaning for a short test? I'd be happy to send money to cover the out shipping. I could do a quick test and ship it right back. Thanks..................Tom

Tom,

I have an SL-40 I bought for my project but decided to go with a SL-30. I can let you borrow the SL-40 in exchange for some photos of it working so I can post them and confirm it is working. Best to reach me by email.
Jaysrv9a AT gmail.com if you want to go that route.

Jay

Garmin Co.

Your experience with Garmin company repair policies is sad. I decided a long time ago that I could not afford any equipment with Big Gs name on it because of the $500 look see or their equipment.

Unfortunately, I have to install a Garmin com. radio into my ELSA-12 as Van's specifies that radio. Hope it doesn't go TU someday but if it does, I'll get rid of it and replace it with a Dynon. Some might call me prejudiced against Garmin but Garmin has, by this repair policy, caused my distain. This is a 'learned behavior. Garmin is not for me.

I'm not going to try to defend Garmin's shop charges. I think that they are ridiculous as well. However, from everything that I have witnessed, they do have solid products. That even goes for the SL40. I just chatted with Steinair about my SL40. He also made the comment that the SL40 was a solid VHF comm. unit, and suggested that I not send it in for service until I swapped out the unit with another SL40. He is pointing me to headset jack shorts as a possible source of my troubles. I will follow up on this post with the final fix............Tom

You can do your own bench test. All you have to do is connect a few wires to the SL40, plus an antenna.
You will need a D-Sub connector, jacks for the headset, and an antenna.
You could even make your own antenna. Change the 8 foot dimension to 23 inches.
The shield is folded back over the outside of the coax.
Pin 1: 12 VDC positive power
Pin 4: PTT Switch
Pin 7: Microphone Ground
Pin 8: Microphone audio input
Pin 9: Power Ground
Pin 13: Headset Ground
Pin 14: Audio Out to Headphone
Why pay Garmin half the price of a new radio to tell you if the problem is in your aircraft or in the radio?

Wow Joe! You can sure come up with some fantastic ideas. This is terrific, and I never thought of it; why, I don't know. I even have and old comm antenna from my old Mooney. Thanks for the pin-out, and I'll let you know how that goes. Thanks a bunch........Tom

Mount that old antenna to a ground plane with a radius of 23 inches or more. It does not have to be solid sheet metal, even wires will do.

Hey Tom
I know you've probably looked at this but This spring I had a problem with my radio and it was a simple fix, my USB charger was a low-end unit and caused big time Intermittent radio problems . , do you have an IPad or GoPro plugged in anywhere ?

Mich48041 said:

Mount that old antenna to a ground plane with a radius of 23 inches or more. It does not have to be solid sheet metal, even wires will do.

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Yeah, I have a 1/2" steel bench block that is about 22' X 30" that should do the trick. I also have sheet aluminum, but I may not need any of it. One of the things that Stein said after I gave him my description of the condition was that the major culprit for hum is headphone plugs and jacks. He suggested that I really check them over closely. Well, the headset plugs were my first stab at fixing this. I pulled them out and re-seated them, but the problem remained. This time, I pulled them out and cleaned them with electronic cleaner and a rag. My stereo plugs are brass, and the mikes are chrome. Anyway, they came out looking like new and everything seems to work. We are about to leave on a 100 mile, $100 hamburger trip here shortly, and that will be the real test.....Tom

Well, all of the severe hum is gone. All it took was cleaning the headset plugs. So Stein was absolutely correct with his theory. Sorry to have raised such a plea for help with such a simple problem. Just goes to show, don't skip over the simple stuff. That was a gotcha that I won't forget soon................Tom