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SL-30 Comm failure

Dave Cole

Dave Cole

Well Known Member
I am seeing a COMM FAILURE on an SL-30. This is on a new installation, new airplane. I read all of the treads on the subject in this forum, and the possible problems were best sumarized by Stein:

1. RS-232 wiring error.
2. COMM wiring error.
3. COMM internal failure.

I have disconnected the RS-232 connections to my EFIS to eliminate that problem, and I have checked the COMM wiring for correct connections with the audio panel.

I still get a COMM FAILURE, starting intermittentaly after several minutes of warmup time during which the COMM frequecy sometimes changes by itself, and the COMM FAILURE message will come and go. Eventuallly the COMM FAILURE message is on continuously.

I am assuming the this is a case of COMM internal failure, unless anyone can add additional insight. Barring that, I am about to the point of sending the unit back to Garmin for repairs. However, I purchased the unit several years ago when I started on my panel, and have forgottten where I got it from (and can't find the receipt).

This leaves me wondering who I can send to for repairs. Any suggestions?
 
Where did you disconnect the RS-232 wires? If from the EFIS I would also remove them from the rear of the SL30. These wires can be susceptible to outside interference.
 
Some thoughts

Proper (full) connector engagement: One thing that can cause problems is intermittent or open pin connections when the SL-30 is installed in the panel. All of these avionics manufactures have their own fool proof installation that can be used incorrectly and not fully seat those two connectors and coaxes in the back. The panel may also blocking the radio from going all the way to the back of the tray. Verify that the radio is properly installed in the tray and that it is fully seated in the tray.

SL-30: After reseating the unit in the tray and fixing any obvious pin engagement problems, I would pull the unit and have it checked by a local avionics shop to eliminate that possibility. You need to eliminate it if it isn't the problem.

Electrical interface: On the comm wiring, you say you checked the wiring to the intercom panel. Did you do this visually or with and ohmmeter? I would check ALL of the wiring (including the coax) from the SL-30 connectors (not just the intercom interface) with an ohmmeter with the intercom and the radio removed and I would check every pin for isolation from the aircraft structure (ground). If there is a ground connection I would verify that it is supposed to be there. Then I would reinstall the intercom panel apply power and check the voltage levels with a volt meter - it could be that in your power circuits you are dropping voltage and making operation marginal. As I ran the tests I would record the actual continuity, discontinuity and voltage results for every pin tested.

Environment: It could be a temperature related problem (especially if the SL-30 has fried components). Do you have vent holes in the glare shield and a avionics fan?

Bob Axsom
 
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I have a friend who had exactly the same issues. we put my sl30 in his tray and it did the same thing, showed comm failure after a period of time. Put it back in my plane, and it is fine. I would suspect wiring issue. Not sure if he has it figured out yet, have not spoke for a month or so. It is most certainly a head scratcher.
 
GREAT PIECE OF INFORMATION FROM GARY WILCOX

Unit substitution shows the problem stays with the airplane and not the SL-30. It would be good to find out what the other fellow is interfacing with and if he has any mechanical installation problem preventing proper pin engagement.

Bob Axsom
 
Bob makes several excellent points.

I'd repeat the thing about checking they tray seating. With the way yours is acting it could definately be an inaccurate fit in the tray. It's not uncommon with the SL's to see people forget to file out the little "ears" on the sides of the panel cutout, which greatly inhibits the unit seating into the tray good and tight - therefore sometimes resulting in weird acting gremlins.

Also as others have also said (but I don't know if you tried it yet or not), see if you can swap with someone. If it follows the radio then you know...if it follows the Airplane then the answer is there.

In the end, you can send your radio anywhere (even though you didn't get it from us, we can easily process the Garmin repair for you).

That's about all I have to add.

Cheers,
Stein
 
SL-30 Comm Failure

I had two widely separated instances of "Comm Failure" messages after Phase 1 testing. I use fuzes vice circuit breakers. After the second one I discussed with the DAR that had inspected my airplane. Turns out the fuze value I had used (3 amps?) was outdated and had been superceded by 5 amp fuze requirements. Installed a 5 amp fuze and have had no problems since.

If you intend to send the unit back to Garmin, be advised the process is in my opinion, bizarre. Garmin insists that the unit has to be returned via one of there authorized dealers. For me, that meant UPS from Ridgecrest, CA, to an avionics shop in Bakersfield, CA, who then just forwarded it (no analysis) to Garmin and charged me $70 to do so.

No one could provide a logical reason why I couldn't ship directly to Garmin.
 
Here is a kinda related question maybe Stien or someone could answer. What power source provides the power for the display n the SL30? The Nav side or the comm side?
 
Gary,
The display on the SL-30 gets its power from the Nav side. If you power up only the Nav side I'd expect to see the "Com Failure" message. If you power up the Com side only you will not see the display however you should be able to transmit and receive on the freq that was last displayed.

Pvalovich,
As a Garmin dealer I would suggest having a customer send me the unit to bench check first. I like to confirm the problem persists on the bench before sending into Garmin. This little step can save a customer the flat rate repair fee. If there is no doubt the unit has to go back for repair its not necessary to ship to a dealer first. The dealer has to contact Garmin and get the RMA number, after all the dealer is the one Garmin is going to charge for the repair. Once the dealer gets the RMA then the customer can ship directly to Garmin. After the repair the unit will be sent back to the dealer. Again I like to have the radio at my shop first in order to try and record any custom setting so that once its fixed I can reset all of the original configurations.

Dave,
Back to your originial issue. If possible you could remove the radio and using a 12VDC power supply (I've even used a battery with alligator clip leads) connect just the power and ground pins on both the Nav and Com connectors. Let it run for a while as see if it fails. Hope this helps.

Jason Smith
Aerotronics Inc.
 
pvalovich said:
....

If you intend to send the unit back to Garmin, be advised the process is in my opinion, bizarre. Garmin insists that the unit has to be returned via one of there authorized dealers. For me, that meant UPS from Ridgecrest, CA, to an avionics shop in Bakersfield, CA, who then just forwarded it (no analysis) to Garmin and charged me $70 to do so.

No one could provide a logical reason why I couldn't ship directly to Garmin.
Click to expand...

The process is that way for several reasons, mainly for one that Jason brings up. Before we send anything off to Garmin for suspicious problems, we check it out ourselves. Over half the time there is nothing wrong with the unit (like a customer last week who thought he had a bad audio panel because he could only hear music in one ear....only to find out his "mono/stereo" switch on his Bose was set wrong).

Also, given the fact Garmins avionics shop/repair station is 100% certified, the FAA has hamstrung them with processes that they can't deviate from. There are a host of other reasons, but in the end believe me it's best for everyone in the long term.

Anyway, nothing much more to add because Jason covered it well! FYI, most of the good shops I know won't charge you much if anything to throw it on the bench for a quick check....

Cheers,
Stein

Cheers,
Stein
 
Comm Failure

Dave Cole said:
I am seeing a COMM FAILURE on an SL-30. This is on a new installation, new airplane. I read all of the treads on the subject in this forum, and the possible problems were best sumarized by Stein:

1. RS-232 wiring error.
2. COMM wiring error.
3. COMM internal failure.

I have disconnected the RS-232 connections to my EFIS to eliminate that problem, and I have checked the COMM wiring for correct connections with the audio panel.

I still get a COMM FAILURE, starting intermittentaly after several minutes of warmup time during which the COMM frequecy sometimes changes by itself, and the COMM FAILURE message will come and go. Eventuallly the COMM FAILURE message is on continuously.

I am assuming the this is a case of COMM internal failure, unless anyone can add additional insight. Barring that, I am about to the point of sending the unit back to Garmin for repairs. However, I purchased the unit several years ago when I started on my panel, and have forgottten where I got it from (and can't find the receipt).

This leaves me wondering who I can send to for repairs. Any suggestions?
Click to expand...

So, I had this exact same problem today. It ultimately turned out to be that I had the serial ports backwards. I had TX from the SL30 connected to a TX port on the Dynon as well as the RX from the SL30 connected to a RX port on the Dynon HDX. Swapped em’ and the SL30 started acting right.
 
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