What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

SL-30 Com Failure

Flying again!

Flying again!

Well Known Member
Last week after I fired up the radios my SL-30 gave me a "Comm Failure" and would not allow me to change frequencies though it did have ATIS (last channel tuned) intermittently. Cycling power gave the same result. After flying, I pulled the radio, checked the pins to make sure they were clean and replaced the radio. Upon power up all was fine until the next morning when i had the same failure again. I removed the radio, cleaned the pins, and reinstalled, still had ?Comm Failure?. :(

I took the radio to a local Avionic shop and he powered it up on the bench and it works fine for a day of periodic cycling etc. So the radio checks out ok on the bench but not in the airplane. He then disconnected the antenna and turned the unit on to see if that would induce the failure (no transmitting w/o antenna). It worked fine with no failure noted.

Question, is there anything on the aircraft side that can induce this failure? The radio is linked to my GRT Sport to enable frequencies to be loaded from the EFIS. With this failure, the GRT showed a failure in the serial communication with the SL-30. I do not think anything on the GRT side could cause the SL-30 to have a ?Comm Failure?.

I would appreciate any thoughts or ideas on this. The installation has worked great for the year I have had the aircraft.

Thanks
 
sl-30 failure

Hi
I had a little different failure. I lost the audio. It was working if i was pressing on the button on the right of the radio.
I was lucky enough that my hangar neighbour is a radar/avionic/man that know everything. He offer me to take a look at it. Since it was out of warranty... why not.
He open the radio and found that the connector that connect the faceplate to the rest od the radio had one pin out. The soldering was of bad quality. It resolder all the connection of this tiny connector and everything work fine now.

Hope it can help you

Lan Vinh Do
 
SL30 Comm Failure

Do a search on "Comm Failure" and you will find several past threads on this subject, and possible solutions.

Bottom line, since it had been working fine for at least a year, here are the most likely causes...

1) Radio not seating fully in tray. Follow the directions in the installation manual to ensure the radio is fully seating in the tray (more accurately the connectors in the rear of the tray). I think this is the most likely problem.

2) Comm power loss. The Comm side has a separate breaker/fuse from the Nav side and the display is powered by the Nav side. Check your comm breaker or fuse, and Comm power and ground wires.

Good luck.
 
Last edited:
I second Paul's suggestions. In addition, I've seen some harnesses that splice the nav and com power leads together. Might check that splice if you don't have separate CBs for com and nav for this radio.
 
sl-30 failure

Just to add that mine was working since 4 years before i had the failure and it was a internal connector.

Lan Vinh Do
 
I had problems with my SL30 powering up and it turned out to be a lose pin in the back plate d-sub connector. If it checked out ok on the bench you may have a similar gremlin. The only way I found it was to jostle the wires slightly and it would power up so I pulled the back plate and checked the power wire pin and sure enough it was not seated completely.
 
Sounds like you don't have power to the comm side, which can occur for a variety of reasons.

If you have a Vertical Power system, you can see if the comm circuit is drawing any current.
 
Thanks for the responses!

Lots of things to check when I can get back to the airport on Friday. Would help if I had a known good SL-30 to try in my -10 to see if it is on the aircraft side.

I looked at the older posts on this issue and it does look like it could be power on the Comm side. I do not have separate breakers for the Nav and Comm side.

Another question, if it is a power issue on the Comm side, how can I still hear ATIS transmissions while the unit display is alternating between "Comm Failure" and the frequencies? At some times, I do not hear the transmission and also cannot hear anything when the squelch knob is pulled.


Thanks again for the ideas on what to check.

TJ
 
It is so often the case it is almost a proverb, but check your antenna and feed line, especially since the behaviour changed when you disconnected the antenna.
 
How many wires are going to the CB? If only one then $5 says it's an intermittent splice where the com and nav power wires are connected together.

Locate the splice, try pushing and pulling on it, see if that makes a difference.
 
I have heard and seen that the 232 feed can cause exactly what you describe. May disconnect it and seewhat happens. Also, should the Nav and com not be on there own power supply? I have mine on two separate breakers as per garmins diagram.
 
A Different Perspective....

This thread jogged some long-dormant memory cells - I think I saw the same message on an SL-30 before, and it has nothing to do with the "Comm" portion of the radio. The message "Comm Failure" is telling you that the unit can't communicate properly over the serial port. Take a look at this thread:

http://www.vansairforce.com/community/showthread.php?t=73352

It might not be your issue, but I think that it is at least another direction to look.

Paul
 
Last edited:
Still Trouble Shooting....

Update...

The radio bench checks ok. When I installed it again (making sure it was fully seated) I found that the SL-30 works ok if the GRT Sport EFIS is off. As soon as the EFIS is turned on, the "Comm Failure" appears and foes away when the EFIS is powered down.

Other threads show that this happened due to wiring errors (Tx to Tx, Rx to Rx). That is not the case here since the wiring was not touched. I also tried to disable the communications to the EFIS via the set-up menu on the GRT Sport, but no luck.

Ideas anyone?
 
Flying again! said:
Update...

The radio bench checks ok. When I installed it again (making sure it was fully seated) I found that the SL-30 works ok if the GRT Sport EFIS is off. As soon as the EFIS is turned on, the "Comm Failure" appears and foes away when the EFIS is powered down.

Other threads show that this happened due to wiring errors (Tx to Tx, Rx to Rx). That is not the case here since the wiring was not touched. I also tried to disable the communications to the EFIS via the set-up menu on the GRT Sport, but no luck.

Ideas anyone?
Click to expand...

But you may have a short or an open circuit that would cause the serial line to fail. That could happen at any time for a variety of reasons. Just get an ohm meter and test continuity. The fact that the SL-30 doesn't work when connected, may imply a short instead of an open circuit. Test both RX and TX to see if they are shorted to each other, as well as to ground. The short could be as simple as a strand of wire in the connector or it could be something that has worn through the insulation after you started flying. Time to go play detective.

bob
 
Check the connector at the Sport GRT for the pins making a good connection. I have had to replace quite a few dsub pins on the GRT connectors.
 
You must log in or register to reply here.
Back
Top