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Garmin GNC250XL comm no worky

R

RV8N

Well Known Member
I have a GNC250XL wired thru a PS Engineering PM1000II intercom. This has worked flawlessly for the last three years. Today I flew to another local airport to buy cheap(er) gas. The comm worked fine the entire time. Shut down and refueled. After I taxied out and performed my run-up, I tried to transmit that I was departing. When I pushed the transmit button, my headset went dead, I couldn't hear myself or anything else (only when I was pushing the botton). After much thought and troubleshooting, I think the problem is internal to the radio.

Here's why:
1. the transmit light on the PM1000 comes on
2. the transmit symbol on the GNC250XL comes on
3. the intercom works normally
4. I tried two headsets in both the front and back, same result
5. nothing else has changed to cause the problem
6. a friend with a handheld could hear a click when I pushed transmit but couldn't here anything I was saying

Here's my question, anybody else ever see this happen with a Garmin or other type radio? What was the cause? Does anyone know if there is an internal fuse that may have blown, failing the transmit but not the receive part of the radio? Anybody have any ideas?
 
Let's see....classic troubleshooting - I like that!

Chances are better than good that there is nothing wrong with the box - after three years, these modern electronics just don't up and quit! If you're getting carrier, along with the fact that you're seeing transmit indications on both the intercomm and the unit, then most likley, that is really what is happening. So that means that you're not getting an audio signal to the transmitter. Since you tried multiple headsets and multiple jacks, and got the same results, it most likely has to be a connection between the intercomm and the radio. It's doubtful that the wires are bad, so...I'd check for a recessed or slightly corroded pin on the connector at either end. I know you just finished the annual - did you by any chance pull on any wires or work behind the panel?

I was having an intermittent loss of altitude data on the serial data line between my transponder and Garmin 430 a couple months back. I removed and replaced the units in the racks, and jiggled and wiggled the plugs and pins - problem gone! (When I had the panel out to install my AlTrak a few weeks after that, I reset all the pins in the plugs, just to make sure it was all good.)

You asked for ideas toget started...!

Paul
 
I know this doesn't sound right but...

It could be the radio is not tight in the mounting tray. Remember the radio conntects to the tray via several connectors that press together at the back. If the connection is spotty, you might get what you are experiencing. Try removing the radio from the tray, then reseating it in the tray and tightening it again. Also try pressing on the front of the radio in various places to see if that makes a difference.

I used to have a GNC-250XL and that is a problem I would occasionally have.

bruce
N297NW
 
I know you probably checked this already, but I'll ask anyway. Are you sure you don't have it set to transmit on COM2 or something and recieve on COM1....and that COM2 maybe doesn't exist? I'm thinking if this is the case, you might not get a side tone since that's generated by the radio, I think.

If this were true, that would also mean there's something else screwy with the wiring or you wouldn't get a transmit on COM1. This would explain, however, why your friend only gets a click on the other end (PTT going to the GNC for whatever reason, but the mic output not getting there). This also all assumes you have an audio panel...

Now that I think of it, if you have an intercom you probably don't have an audio panel....so nevermind :)
 
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I removed the radio from the tray once, inspected it and replaced it. I didn't look back in the tray to inspect connector pins. I will have to do that. I will also call Garmin techincal services tomorrow... and possibly our local avionics shop. Thanks for the ideas, keep them coming.

Karl
 
MSFT-1 said:
It could be the radio is not tight in the mounting tray. Remember the radio conntects to the tray via several connectors that press together at the back. If the connection is spotty, you might get what you are experiencing. Try removing the radio from the tray, then reseating it in the tray and tightening it again. Also try pressing on the front of the radio in various places to see if that makes a difference.

I used to have a GNC-250XL and that is a problem I would occasionally have.

bruce
N297NW
Click to expand...

Check and Re-Check this! This is the MOST COMMON problem with audio/comm troubles in the GNC series of units. It's not rare at all, and is frequently the culprit of weird or intermittent type failures in these units.

Take it out, slam it back in a couple times and see if that helps. If not, then obviously it's something else, but I've seen this many times on the GNC's in flying RV's with nearly identical symptoms.

Cheers,
Stein.
 
Exact same thing happened to my 250XL, lights, click, etc after 2 years----A trip to Garmin and $400 bucks fixed it. No clue what the problem was but it was definately the unit.
Larry
 
I was finally able to get back to the airport last night to try removing/installing and wiggling the radio in the tray. No joy. I also inspected the connector pins in the back of the tray and on the back of the radio. All looked normal. Finally I borrowed a friends GNC250XL and installed it in my plane. It worked fine and transmitted as it should. Re-installed my radio and still no joy. The radio will be shipped to Garmin today for a $400 rebuild/repair. It hurts to spend that much money but I see no other option.

Karl
 
Very quick turn-around!

While I am not happy with the flat-rate repairs that Garmin does, I must say that they got my radio out in about 1 day! I shipped UPS overnight on Wednesday 5/17 and had a DHS attempted delivery ticket on my door yesterday (Monday, 5/22). Very fast. Hope the radio is fixed right.

Karl
 
Fixed my GNC 250XL today

Just thought that I'd put my two cents in on this thread. Last night I brought home both my GPS's to do some programming while sitting in my chair and watching TV. When I bought my radios originally I also bought the wall transformer so that the 250XL could be powered up at home off 115ac with just these kind of occasions in mind.

After programming all the routes in to get from San Jose to Oklahoma, and a couple of other upcoming trips I had the gps in the simulator mode and it was flying the last leg into Oklahoma when it went blank. This is the first time this radio has acted up and this thread came to mind right away. I found that by sqeezing the top and bottom cover the display would light up again until pressure was released and then it would go dark again. Eventually I was able to isolate this to the bottom cover and pulled it to give it a peek. Underneath there is a ribbon cable from the power switch to one of the boards. Today I took the radio to work and did a continuity check on the ribbon connector and it was bad. A couple of minutes and a couple of jumper wires and the thing works perfectly. Actually I installed jumpers to parallel all 8 runs in the ribbon assuming that the pressure from the case has probably compromised them also.

Since some of you are finding that reseating your radio seems to fix it I'm thinking that there is a chance that you are just applying pressure to your ribbon cables and moving them very slightly as the rack sqeezes the covers slightly.

Regards,
 
Bryan Wood said:
Since some of you are finding that reseating your radio seems to fix it I'm thinking that there is a chance that you are just applying pressure to your ribbon cables and moving them very slightly as the rack sqeezes the covers slightly.

Regards,
Click to expand...

Unfortunately I could not fix mine by reseating it. The paperwork that came with the radio said that they tested and found that the transmit was not functional. They repaired the CPU board, replaced the comm antenna BNC connector, and replaced the all front pieces (cosmetic). I will go to the airport tomorrow and install the radio. Hopefully it will work fine.

I have had only one glitch with the GPS side of my radio. On the way to Oshkosh in 2004, we stopped in Iowa for gas and I put the Ripon waypoint into the radio. As we were approaching Ripon the 250XL crashed and re-booted. I didn't see it the first 2 times so was confused as to why the GPS was searching for satellites. I was finally looking at it when it rebooted again. I just kept putting in Direct-to Ripon after each re-boot. The last time it crashed, I told my girlfriend to fly while I re-set the GPS (we were very close to Ripon). She said "There's a plane to the left." I looked up and there was a C-172 on a parallel course about 200 yards off our left wing. I said "I've got it", pulled power and did a fairly radical left/right to get behind the C-172. We followed them up the railroad tracks then made the right turn to land on runway 36.

I can't remember if the GPS crashed when we were departing Oshkosh but it was fine for the rest of the trip and has never done it again. I think there was something screwy about the Ripon waypoint or the way I stored it and the GPS kept tripping on it.

Karl
 
GNC250XL

Hi,

I have the same problem on my GNC250XL--transmit doesnt work some times--totally dead mike with no audio feedback TX on unit and the intercom on activation of the PTT--have reracked it twice--used CRC contact cleaner on the pins--worked --then went dead again--how have you guys sorted it out?
 
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