Radio Question

Geico266

Geico266

Touchdown! Greaser!
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Husker Nation, NE
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Geico
I have a predictable intermittent radio problem with a Garmin GTR 225.

The radio in my new (to me) helo works fine when I start the day, but no side tone. Later on when things get warm (an hour or two) the radio quits transmitting. I can hear incoming, but cannot transmit.

A clue is the "TX" (transmit light) on the display is suppose to appear and be steady when transmitting. When it is not working it flashes.

Another clue is the ICS intercom indicator normally turns red when the intercom is in use, and turns green when transmitting on the radio. When the radio stops transmitting the light just turns red.

Is the radio heat sensitive or the intercom? Suggestions?

I have adjusted the side tone volume per the installation manual, but have not flown it yet. Nothing in the manual that I can find talks about the "flashing TX" indication and what that means.

Thanks in advance for your suggestions and comments.
 
Last edited:
Many electronics will fail when they heat up. So on the bench they will not fail. Probably can be traced to a cold solder joint on a board
 
Geico266 said:
I have a predictable intermittent radio problem with a Garmin GTR 225.

The radio in my new (to me) helo works fine when I start the day, but no side tone. Later on when things get warm (an hour or two) the radio quits transmitting. I can hear incoming, but cannot transmit.

A clue is the "TX" (transmit light) on the display is suppose to appear and be steady when transmitting. When it is not working it flashes.

Most of us use that flashing red circuit to indicate when the transmitter driver loses lock and cannot provide a stable frequency to the transmitter.

Any decent shop has what we call a "hot box" that is nothing more (at least in my case) than a picnic cooler with an incandescent light inside with a thermometer that will cycle the light on and off at a particular temperature. The radio is put inside with thermally insulated wires going into the hot box to power the radio. When it craps out we QUICK pull the radio out, put it under a heating pad, and start troubleshooting. If the radio cools down to working temperature then we repeat. It is a time consuming process but a hell of a lot better than "shotgunning" by replacing parts until you hit the magic one.

Sorry, but this is NOT something you can troubleshoot for yourself. I rarely suggest going to an avionics shop, but that is where you are headed. But ask to see their "hot box" and if you get a dumb look in response, the door is right behind you. Go out that door to another shop.
Another clue is the ICS intercom indicator normally turns red when the intercom is in use, and turns green when transmitting on the radio. When the radio stops transmitting the light just turns red.

That is just a function of the inoperative transmitter. Solve the transmitter problem and the intercom problem goes away.

Is the radio heat sensitive or the intercom? Suggestions?

I have adjusted the side tone volume per the installation manual, but have not flown it yet. Nothing in the manual that I can find talks about the "flashing TX" indication and what that means.

Thanks in advance for your suggestions and comments.
Click to expand...

Jim .....
 
yetti said:
Many electronics will fail when they heat up. So on the bench they will not fail. Probably can be traced to a cold solder joint on a board
Click to expand...

Since all factory radios these days are wave-soldered can you please elaborate on how you think this is possible?

Cold joints are a function of hand soldering that went out the window about forty years ago.

Jim
 
Since no one does board level repair anymore, the discussion is a waste of Gopher Electrons
 
yetti said:
Since no one does board level repair anymore, the discussion is a waste of Gopher Electrons
Click to expand...

I do. I have a lot of acquaintances in the biz that do. Are you saying that we are all nobody? THen who in the hell are you to make that pronouncement?

Jim
 
A tall mythical creature that is rarely seen in photos.
 
weirdjim said:
Since all factory radios these days are wave-soldered can you please elaborate on how you think this is possible?

Cold joints are a function of hand soldering that went out the window about forty years ago.

Jim
Click to expand...

We build, test and ship two or three thousand boards a year. All of them are a mix of surface mount and through-hole and they get waved and reflow soldered. Any number of things can cause a defect that looks and acts like a cold solder joint. Leads bent, old solder paste, or an incorrect reflow oven temperature profile are the most common culprits.
 
Garmin charges a flat fee of $650 to repair the radio. I'm leaning towards just do this. I have a couple of buddies that want to look for an obvious solder problem. They don't have a "hot box, they just want to have a look see. I guess that couldn't hurt. :dunno:


Thank you one and all for the responses. I really appreciate it.
 
Old Geek said:
We build, test and ship two or three thousand boards a year. All of them are a mix of surface mount and through-hole and they get waved and reflow soldered. Any number of things can cause a defect that looks and acts like a cold solder joint. Leads bent, old solder paste, or an incorrect reflow oven temperature profile are the most common culprits.
Click to expand...

That's interesting. THings seem to have gone into the dumper in the last 20 years then. At Teledyne we also did a few thousand boards a year and once we put them through initial stress testing (thermal, shake/rattle/roll, etc.) and then through final QC we had less than 0.1% field failures and most of them were components, not pcb solder joints.

Not to mention the ones we did for Apollo where we x-rayed each and every joint before putting it on the bird.

Jim
 
weirdjim said:
In that case I believe that the correct spelling is Yeti.

Jim
Click to expand...
Unfortunately the tribal lawyers screwed that up and that spelling was lost to the likes of corporate types of Yeti Bike and Yeti Coolers. We have to press on with the new spelling and hope the lawyers have proper trademarks in place.

I put myself through college doing two way radio work. One of the easier fixes was to wack the transceiver unit with a hard hat which would reseat the board to board pin sockets getting the cement dust and associated corrosion such that the pins made contact again. One of the first trouble shooting things to do on mainframe IBMs was to re seat all the boards...
 
Whoa! I fixed it! :eek:

I'm a firm believer in studying the problem. I went flying for 5 hours today and could not get it to duplicate the problem until a "cold start". Then I tried to turn the radio off and on and it reset and worked great! Talked to ATC and everything! :yes:

So my next step is to start the engine with the radio off and see how that works. Saved me $700 so far! :thumbsup:
 
yetti said:
Since no one does board level repair anymore, the discussion is a waste of Gopher Electrons
Click to expand...

There's a shop over in Gainsville that does. Actually a lot of Good shops do.
After all, why swap a board for a popped cap, or toasted transistor?
 
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