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Noob Question ... Stuck and/or Not Responding to Controls

Noob Question ... Stuck and/or Not Responding to Controls

Old 05-18-2010, 12:57 PM
  #1  
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Default Noob Question ... Stuck and/or Not Responding to Controls

My son has an OFNA Ultra LX that is about a month old. (both of us are new to this hobby) He's gotten most of a gallon of fuel through it, and hasn't done anything with it but run it up and down the street... some dirt at the park, but mostly on the street.

It was running fine up until a few days ago, when the car just "ran off" at full speed.

He went and got it... restarted it... and it ran fine for the rest of the day.

The following day, the car "ran off" again... was fine for awhile... then "ran off" a third time. It was at this point he asked me what was happening.

I immediately thought that the batteries in either the controller or the receiver were bad... he'd been running it awhile and neither one of us know how long they would normally last, or what would happen when they wear out... so it seemed like a reasonable explanation.

We replaced the batteries in both receiver and controller and then started the car and the throttle got stuck (we were holding it.. so it didn't "run off" this time).

We stopped the car but from that point on the car doesn't respond to the controller at all... no steering, no gas... notta.

All connections are good, I know the batteries are fresh, etc.

So... I'm not sure what to do/check next.

Any help would be appreciated.
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Old 05-18-2010, 01:40 PM
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Check all the connections into the rx, unplug one servo at a time and see if it comes back to life as a dead servo can some times short the system out, RTR radio systems are usually problematic at best and there are some good cheap upgrades available. Also check by wiggleing the battery holder and batterys for the rx and make sure the connections there are good, those little plastic 4aa holders can be fragile .

Also look into a failsafe, goes inline with the throttle servo wiring and makes it so if it loses signal it will set the servo where you set it to, most likely full brakes. but if its losing power and not signal wont really help.
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Old 05-18-2010, 02:07 PM
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Also re-seat both crystals. Check antenna wire for any bare wire, especially if close to chassis - run wire in fuel tbg where close to chassis.

If you can't solve prob by checking connections, next step would be to suspect bad rcvr.


Def invest in a fail safe -

http://www3.towerhobbies.com/cgi-bin...?&I=LXEYG2&P=7
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Old 05-18-2010, 08:16 PM
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first of all, make sure u power on the TX first then the RX... when power off, first the RX then the TX, always make sure ur servo and throttle linkage are at neutral before u start...
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Old 05-24-2010, 06:21 PM
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I couldn't figure out what was happening so I took it to the LHS.

As a test, they bypassed the power switch on the car and everything worked fine.

After he put it all back together, since he didn't have the part we needed, we tried it again for the heck of it, and everything worked.

I dunno if he had the magic touch, but I swear we did the same thing at home. lol
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Old 06-06-2010, 09:49 AM
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Ok...I'm back.

The problem is still happening... after 2-3 minutes of running the throttle will stick open. I can't make it stick when it's not running, even if I repeat the same pattern I did when it was running.

I monitored the car running while stationary and noticed that the throttle will stick open... i.e. when I release the trigger the servo does not always return to the idle position.

When the car isn't running it always snaps back... at least so far in my testing.

Something else I noticed during the last test is that if I touch the glow-plug heater to the heatsink the servos twitch (as long as I have the power switch on). If I run that heater up and down the fins they twitch on every fin.

This could be normal... I don't know... I just happen to notice it.

Also I noticed that the throttle trim is turned all the way one direction.... is there something I can change so that we can leave it more in the center so there is still some available adjustment?

Any ideas of what I can look at before running it up to the LHS?

Thanks,
-TK
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Old 06-06-2010, 10:31 AM
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You might try to re-center the throttle servo - take the servo horn off and then turn the car on. Let the servo re-center then without moving the servo drive spline, put the arm back on, then turn car off. When you turn radio on set trim back to zero and turn car on. See if it is any better.

If servo had gotten off center, this should make a diff. If servo was not off center, you'll have to add the trim again to get back where you were.
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Old 06-10-2010, 07:44 PM
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Okay... Finally got it to the hobby shop today.

Told them the whole story and the consenus was that there was a "radio" glitch... but the only way to test would be to swap out the radio system.

While I was thinking about how much I wanted to spend on a replacement he said... maybe it's the crystals.

So I figured for $10 we would try that first.

That was it.

The theory is that at some point the crystal in the receiver got jostled loose inside the container... it worked fine while the car was not running but the rattling from the engine shook the crystal and the receiver went crazy.

So $10 worth of crystals fixed the problem.

Now to contemplate replacing it with a better system.

Thanks for everyone'e help.

I'm sure I'll be back with more questions.

-TK
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Old 06-11-2010, 03:49 AM
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FWIW, that doesn't happen very often so you might not ever have teh prob again. Glad you got it fixed!
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