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Bad crystal or switch....help!!!

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Old 09-24-2004, 06:55 PM
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mar345
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Default Bad crystal or switch....help!!!

While checking my radio operation everything just froze and would not respond to the transmitter until I pushed the receiver power switch off and on again. I played with the switch and could not reproduce the failure. So I checked my connection to the battery and sprayed the connector and the switch with electronic grade contact cleaner and put it back together. Today when I first turned in the power to the receiver it responded to the transmitter and then the failure reoccurred. Everthing froze and would not respond until I again pushed the power switch off and then on again. Then it operated normally. While playing with the switch I seemed to notice a lag in response from the servos when power was turned on. Usually the servos jump a little as soon as power is applied. On one instance they seemed to lag a second or so. All of this intermittent operation started shortly after the plane spun in. It was repairable so I wouldn't say the receiver was subjected to a severe crash. Anyone have similar problem and what to do about it ?? I flew the plane today without incident but am spooked .....help appreciated.
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Old 09-24-2004, 07:41 PM
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Default RE: Bad crystal or switch....help!!!

Check the connections to the receiver - especially where the battery plugs in to the rx. If all is tight here, then I suspect a more severe problem. Cracked crystals (or loose crystal) can give intermittent failure like this. Try knocking the rx around with a stick while the system is on. You are looking for a vibration sensitive failure or intermittent connection. Don't knock the rx so hard as to damage it of course, but shake it around and tap it with a small stick to see if you can reproduce the problem. also wiggle all the wires goind in to the rx.
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Old 09-24-2004, 08:38 PM
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Default RE: Bad crystal or switch....help!!!

The system was subjected to some vibration when I flew it today and no failure occured. It seems to fail within a few minutes after power is first turned on and then resumes normal operation after the power switch is cycled off and on again. Its as if the power surge gets it going again. This failure and resumption of normal operation after turning power off and then back on has occurred with the engine off and running while on the ground. This usually happens before the first flight of the day and doesn't happen again until after recharging. I'm using a four cell NIMH pack. I think so far I've been lucky not to lose the plane and am reluctant to fly it again until problem, whatever it is, is solved.
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Old 09-28-2004, 07:45 PM
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Default RE: Bad crystal or switch....help!!!

I can't reproduce this failure by tapping the receiver with a stick. Everything works ok for now on the bench. I did notice that if I hold the transmitter a certain way , my finger hits the trainer switch and disrupts the signal from the transmitter. Could that be what happened at the field?? If I hit the trainer switch without the trainer cord to another transmitter attached, I get the same type of glitch. Just as if transmission or reception is disrupted and everything just freezes. Well I can watch for that in the future, but for now would it be prudent to send the receiver back to Airtronics for a check?? What do you guys think on this one?? I'm still leary about flying it until I know.
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Old 09-28-2004, 10:37 PM
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Default RE: Bad crystal or switch....help!!!

There is the possibility that the switch between the receiver and battery is getting worn or possibly dirty and corroded. Switching it off and on may clean the contacts just enough to restore the connection and make it work again. Sometimes contact cleaner which you used is not enough to make a worn switch reliable again.
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Old 10-20-2004, 08:28 PM
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Default RE: Bad crystal or switch....help!!!

Sent receiver back and it checked out ok. So, took switch apart and found powdery green corrosion on solder connections on back of switch where wires are soldered on. Some very brittle and wires fray easily. The switch slide contacts looked clean. Using NIMH battery pack kept on trickle for about a year. Switch is fairly new and from a major manufacturer. Wondering what kind of flux was used to attach connectors????????? Very disturbing!!!!!!!
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Old 10-20-2004, 11:41 PM
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Default RE: Bad crystal or switch....help!!!

Have you tried wigglinng the battery pack and its leads? The problem could be in the pack or wiring. Have you discharged the battery pack to measure it's capacity? What is the capacity of your battery pack, and at what rate did it stay on trickle for a year? How many milliamps?
The more information you give, the more help you will probably get.

Hope this helps,
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Old 10-21-2004, 09:24 PM
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Default RE: Bad crystal or switch....help!!!

1450 mah NIMH battery pack. On trickle at 25 mah.
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Old 10-21-2004, 10:26 PM
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Default RE: Bad crystal or switch....help!!!

Discharge the pack and check for capacity. If you have a cell that's messed up, or bad connection in the pack or lead, it will probably cause the discharge to cut off early giving a low reading. Wiggle the battery pack and wiring a few times during the early part of the discharge.

You are obviously going to replace the switch, now that you have taken it apart. This should help to eliminate another potential offender.

Hope this helps,
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Old 10-24-2004, 08:19 PM
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Default RE: Bad crystal or switch....help!!!

Remember to weigh the risk and reward while working with this. I'm sure you've heard this before. rc airplanes can be dangerous while out of control. Not to mention picking up parts BITES. Replace the 5.00 dollar switch (I try to replace all batterys and switches at 2 years) and send the crashed reciever to the factory to have it checked. Sounds as though it could have a cracked board. It has been a common practice for most oldtimers to send crashed electronics in to be safe. Hitec has always been pretty good about fixing things free or at a low cost. Futaba not so low cost. Still cheaper than another plane.


Best of luck
Robert
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Old 11-01-2004, 04:05 PM
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Default RE: Bad crystal or switch....help!!!

I agree with Robert. It sucks to lose a $500 - $5000 plane because of a potentially bad switch, switch connector, or potentially flaky receiver. In the same condition with any of my birds, I would replace the switch AND have the receiver checked out by the manufacturer. It may be a bit of a pain but turning your plane into a bag of sticks is more painful.
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Old 11-06-2004, 07:35 PM
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Default RE: Bad crystal or switch....help!!!

I agree. Receiver was sent to manufacturer. They replaced a "bad" antennae wire and said the receiver checked out ok. I think they may have also replaced the crystal as the identifying mark that I put on it before sending it back was gone. Replaced the switch with a heavy duty one and installed a new Nicad 1100 mAh battery pack. The old pack checked out ok but replaced it anyway. System checks out ok and will check it out with engine running next time I go to the field.
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Old 11-08-2004, 10:33 PM
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Default RE: Bad crystal or switch....help!!!

I wonder if it might have been the NiMH battery pack? Anyone hear of glitching problems traced back to NiMH battery packs??
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