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Old Nov 18, 2005, 10:36 PM
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Cincinnati Cin N.Knty, Ohio, United States
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Throttle servo moves when elevator servo is moved

Like the title says, my throttle servo moves when I move the elevator stick on my radio. It just started doing this tonight. At first I thought it was just one plane, but tried my other one and it does the same thing. My radio is a Futaba 7chp. When the elevator stick is moved, the throttle servo moves about a quarter of an inch, and moves a different direction depending on which way you move the stick. Any suggestions will be appreciated.
Thanks,
Chris
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Old Nov 18, 2005, 10:59 PM
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have u tried reseting the Parameter to Aerobatics?

It sounds like theres a MIX that is enabled..

-Tomi
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Old Nov 18, 2005, 11:35 PM
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I checked all the mixes, they are all inhibited.
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Old Nov 18, 2005, 11:39 PM
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there's also a strange inter-relation in some computer radios such that when one pot starts going bad it affects other channels.

Life expectancy of a pot in a TX is anywhere from 5 min to 20 years... MTBF (mean time between failures... look at it as the time before the FIRST pot should fail) appx 9 years. You can be the unlucky guy and have it fail while first testing a TX... (but then it would be replaced under warrantee)
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Old Nov 18, 2005, 11:55 PM
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Did you try a different model number? If it's still doing that, I'd send it in
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Old Nov 19, 2005, 12:06 AM
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Yea I tried it on different model numbers, looks like I will be sending it to Futaba to have it checked out.
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Old Nov 19, 2005, 09:59 AM
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Anybody know what the turn around times is from when they recieve my tx and I get it back?
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Old Nov 19, 2005, 12:37 PM
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Sent my series 8 back for some dumb thing. Got it back within one (1) week.
If it is not warrantee, there is a cost involved. Go to their site and get all the info first, like a return policy etc.
HTH.
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Old Nov 19, 2005, 02:56 PM
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Dpending on what Futaba tells me after they recieve my Tx, if it can be fixed and if buying a brand new one will be about the same price as if they fix my old one, what is the difference between PCM and FM? I seen on Towers website that a FM radio is a little bit cheaper than a PCM. All I fly is planes, no heli's, just wondering what the difference is and which one is better.
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Old Nov 20, 2005, 02:21 AM
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Most of the high end radios are equipped with selectable PCM. In order to use PCM you need to have a PCM RX. They cost a bit more.. But they clean out any RF noises and keeps the signal clean. I own one on my heli, but I feel that I dont need any for my planes. Unless my plane is like $1500 or more..

-Tomi
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Old Nov 20, 2005, 06:47 AM
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Do you happen to have an 'open' spot on your tx for another plane? Just as a test, try loading your plane into that spot after you make sure that that spot has been reset. I agree that the fault seems to lie in the tx.

Also, swap the throttle with, say, the elevator servo lead. I'm assuming that the problem will move to the elevator servo.

Yeah, I agree with Tomi, that it seems like the tx is acting as if it's in heli mode on power-up, or something like that...

I'd be interested in finding out what your test and/or Futaba says.

Bob
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Old Nov 20, 2005, 09:04 AM
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PCM doesn't really clean out rf noise... It uses a digital "encryption" instead of a pulse proportional signal. the digital signal is easier for the RX to check if interference has made a "frame" invalid or not. There's a small computer chip in the RX which stores "failsafe" and "last valid" servo position information. the computer compares the new frame with the last valid and with a check of the digital encoding. If the checks fail in just one frame, then the RX does nothing (servos stay at the last valid positions). If the checks fail for a programmed numer of times within a programmed length of time it sends the servos to the failsafe positions.

A PPM (FM) RX has no logic check and a bad frame goes straight to the servos. a single fram can only move the servos so far due to servo travel speed, so the controls "jump" and buzz. many bad frames in a short time wil send the servos to whatever positions the RX interprets as correct.

actually both PPM and PCM signal encoding can be AM or FM. ANd you can have single conversion or dual conversion signal processing for noise filtering in either RX type.

PCM does not really filter out interference... it rejects bad data. In a way its like the dofference between someone randomly marking all the "T" boxes on a true-false test and someone that actually reads the questions, and sees that a few should be "F" instead of "T" (but the rest are all True...). The one that reads the questions is going to get more answers right. (with right answers being seen as good servo response)
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Old Nov 20, 2005, 11:31 AM
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Quote:
Originally Posted by chris8105
Dpending on what Futaba tells me after they recieve my Tx, if it can be fixed and if buying a brand new one will be about the same price as if they fix my old one, what is the difference between PCM and FM? I seen on Towers website that a FM radio is a little bit cheaper than a PCM. All I fly is planes, no heli's, just wondering what the difference is and which one is better.
.
I send stuff to Futaba, with an explanation of what I think is the problem, my VISA number, and tell them to fix it.
It seldom take long, and any replacements are usually billed at 50% of market value which is much lower than buying a replacement.
There's no need to have snail mail or phone messages involved this way.
It's cheaper to send it back and get it fixed than to buy new.
Sometimes the fixes are free.
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Old Nov 20, 2005, 12:45 PM
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N1EDM, tried all that, tried with two different planes, and tried with a reciever that wasnt in a plane, tried different model numbers on the Tx, reset a model number and tried it and it did the same thing. I would say its definitely the Tx. Futaba support is emailing of things to try with the Tx. I will let you guys know what the problem was when it is fixed.
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Old Nov 20, 2005, 08:23 PM
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Good luck with it, Chris. We'll be interested in finding out what is causing this.

Bob
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