Had to replug Tx crystal during flight !! - RCCanada - Canada Radio Controlled Hobby Forum
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Old 07-27-2016, 07:05 PM   #1
east6008
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Had to replug Tx crystal during flight !!


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Its an FM Hitec Tx on Ch 49. While thermaling high up she stopped answering the helm, desperate, I cycled the Tx switch. Then followed a death spiral. Somewhere, I remembered another Hitec FM Tx I have, that acted up after sitting in the hot sun. Replugging the crystal cured it. So, at about 300 ft above trees, I clawed out the crystal and replugged it. SAVED !
I have since cleaned the pins on the crystal with an emry board, and hope this is the end of the problem, as I cant find a ch 49 crystal for this radio. The disturbing thing is, I condemnded and through out 2 recievers, and I think this was my problem all along. I wonder if Tx crystals go bad?
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Old 07-27-2016, 08:47 PM   #2
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Re: Had to replug Tx crystal during flight !!

Have receiver crystals if need 49 and also 58s. If you upgrade to module based radio Have a 58 TX module.
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Old 07-28-2016, 06:59 AM   #3
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Re: Had to replug Tx crystal during flight !!

Lots of things can go wrong if temps are extreme. Don't forget this stuff isn't built to aviation or mil spec tolerances.

I lost a PC9 a few years ago and traced it to leaving the Tx next to the plane on the starting line for a bit too long. It was the hottest day of the year. Consequently cover the center section of the aircraft and keep the Tx's hidden in their cases till ready for flight.

Cannot come up with any direct reason pulling and reinserting the crystal would make a difference. I can think it would drift with extreme temp changes, but wonder if the simple act of touching it to do this cooled it off enough.
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Old 07-28-2016, 07:06 AM   #4
Dave Holmes
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Re: Had to replug Tx crystal during flight !!

At least you had a save! Some years ago I took off with my Piper Cub and was about fifty feet in the air when something hit my right foot. I glanced down and saw the Tx battery pack beside my toes. OOOPS!

Oxidation on the crystal pins and in the socket can add up to high resistance and the crystal is no longer getting sufficient voltage to cause it to oscillate. Hence Tx stops sending a signal. Unplugging and re-inserting cleans enough of the oxidation of so connection is remade.
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Old 07-28-2016, 07:55 AM   #5
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Re: Had to replug Tx crystal during flight !!

I think a situation like that would scare me enough to scrap the radio. I was a very late convert to 2.4 but honestly I got a lot of great years out of my 72mhz gear so it was time. Lets face it modern electronics are amazing compared to the early stuff but sometimes they just fail. If it happens again it could be the end of a nice glider/plane. Just my .02 but consider how unnerving it is flying with gear you don't have complete faith in.

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Old 07-28-2016, 08:08 AM   #6
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Re: Had to replug Tx crystal during flight !!

What receiver were you using. Possible to have maxed out range of it and when it spiralled down it then hit range?
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Old 07-28-2016, 09:37 AM   #7
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Re: Had to replug Tx crystal during flight !!

Never heard of maxing out distance on 72 MHz before ,as loss of sight usually happens. Of course ,providing that there is no interference from other radios on the same channel or things like that.
Have never heard of crystals going "bad" but they can be damaged from shock such as being dropped or in crashes.
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