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Futaba 9c: lost radio link to 148DP receiver

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Old 01-27-2008, 01:23 AM
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nonstoprc
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Default Futaba 9c: lost radio link to 148DP receiver

Today at the field, my 9C radio acted strangely when I tried to run dry my DA50. As usual, I turned on the 9c, the receiver and ignition and flipped the prop. DA50 immediately went to full RPM. Luckly, the plane was restrained and the full RPM lasted only about 10-15 seconds before it ran out the fuel.

During that time period and about 2 minutes followed, I attempted to throttle it back and there is no response from the throttle servo, and in fact there is no response from any servos at all. We turned the receiver off and back on. Same deal - no reponse. We turned the radio off and back on. Same deal - no response.

After several off/on attempts, the radio link finally came back and all servos responded properly to radio control stick movement. We then checked the receiver voltage of two redundency packs and both are about 5.9v (5-cell Nicads), which are high enough to not trigger the fail-safe mode.

Here is the summary of the strange things observed at the field:

1. the engine directly went into full RPM, even though the throttle position on 9c is at idle on radio. Before the run, I am pretty sure the throttle is at the idle position (after last landing)
2. no radio link for about 2 minutes.
3. radio link finally came back and everything is normal.

Played with the radio and receiver at home and could not reproduce the problem.

Anybody has similar experience? Any theory that can explain it?

The radio was set on PCM mode.


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Old 01-27-2008, 05:42 AM
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Default RE: Futaba 9c: lost radio link to 148DP receiver

I would check your antennae connection inside the radio first.

I seem to remember a thread some time ago talking about soldering problems on the 149DP. Broken solder joints in the RX, from a new manufacturing process, causing intermittent failures.
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Old 01-27-2008, 08:16 AM
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Default RE: Futaba 9c: lost radio link to 148DP receiver

I would send it in and get it looked it. That have had some problems with vibration or crashes that caused a problem with the crystal filter, make sure whomever you send it to knows that you suspect its a vibration related issue.
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Old 01-27-2008, 01:15 PM
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Default RE: Futaba 9c: lost radio link to 148DP receiver

Dito on sending it in. Send both receiver and transmitter. The bit about the crystal filters is good info. I had two receivers that had them replaced in the last year. Both were sent in after crashes for a checkup. One thing I've learned after 40 years working on computers is that problems like this don't cure themselfs. It's going to show up again and it may be in the air the next time.

Don
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Old 01-27-2008, 02:02 PM
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Default RE: Futaba 9c: lost radio link to 148DP receiver

Sounds to me like it could be a couple of things,,,how about your battery connections in your plane,,or has this reciever been in a crash before,,,,is the reciever mounted on foam to absorb vibrations....is the antenna screwed into your Tx all the way
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Old 02-03-2008, 07:55 AM
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Default RE: Futaba 9c: lost radio link to 148DP receiver

I had a similar problem with a 7C and a R138DP , fueled it up ,range checked it ,then while trying to start it the receiver failed. After I fussed with batteries , checked the crystal , nothing. I switched the crystal with another plane and it worked , switched back and it still worked. Tat crystal and receiver have been shelved , can't quite trust them.

Andy
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Old 02-03-2008, 09:18 AM
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Default RE: Futaba 9c: lost radio link to 148DP receiver

The receiver was never involved in a crash and the radio is about 2 years old. The receiver is wrapped in foam and placed about 30 inch from the engine.

I have sent both in for a check-up. Let see what Futaba Service find.

Thanks for the feedback.

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Old 02-03-2008, 01:32 PM
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Default RE: Futaba 9c: lost radio link to 148DP receiver

Futaba will never tell you this,,but i know for a fact with the 9C's since theres about a 10 different people where i fly using them,,sometimes,,you turn it off,,take a brake turn it back on ,and all the trims have changed,,even sometimes the programing has changed and you have to go back reset some th ings in the radio,,doesnt happen very often but it does happen,,and on the 138DP rec's there really prone to acting up,,low batteries really mess with them,if your ever flying and you lose the throttle,,its from low battery,,move the stick to idle and back up,,you will have throttle control for another 30 seconds,all you lose is throttle control,,nothing else,,low battery,,the throttle is the first thing you lose..

Bob
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Old 02-03-2008, 02:51 PM
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Default RE: Futaba 9c: lost radio link to 148DP receiver

Is the throttle back when battery is low a feature (false-safe)?

I have not experienced trim lose with the 9C. Overall, I am pretty happy with the radio.
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Old 02-03-2008, 03:08 PM
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Default RE: Futaba 9c: lost radio link to 148DP receiver

Yes throttle to idle is a built in feature when there is a low battery,,set throttle to idle then back,you have throttle for another 30 seconds,then it goes to idle again,,not sure how long youve had your 9C,,but the ones here all do it once and awhile,or when you change models and go back to one,everythings screwed up,,doesnt happen very often but it does happen,,

Bob
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Old 02-03-2008, 05:22 PM
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Default RE: Futaba 9c: lost radio link to 148DP receiver

I've got two of the 9C's, one a supper and an older one. The only problems I had with the setting "changing" was when I was on the buddy box, I found that the throttle didn't give full travel on the buddy box when it did on the 9C. The only other times that "something changed" on me was when I had tried some program changes the night before and forgot to change back the known good model. I keep one model for playing with the settings and when it looks good, then I make it the new "master" for that model.

Don
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Old 02-04-2008, 09:34 AM
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daven
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Default RE: Futaba 9c: lost radio link to 148DP receiver

Did you fly a different plane with the same transmitter prior to the problem?

I know if I switch between a PPM model and a PCM model, you have to turn the radio off and then back on to get it into PCM.

Not saying this is the problem, just curious.
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Old 02-04-2008, 09:52 AM
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Default RE: Futaba 9c: lost radio link to 148DP receiver

You say that the batteries are 5 cell and that they where 5.9. Was that with a load or not. A 5cell pack will have 7v freashly charged and will sit a 6.6v most of the day. If 5.9v without load would mean that you had not enough battery. I recharge a 6v. Never let a 5 cell go below 6v. A 5 cell battery will not fly your plane to 4.8v. Dennis
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Old 02-04-2008, 02:26 PM
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Default RE: Futaba 9c: lost radio link to 148DP receiver


ORIGINAL: daven

Did you fly a different plane with the same transmitter prior to the problem?

I know if I switch between a PPM model and a PCM model, you have to turn the radio off and then back on to get it into PCM.

Not saying this is the problem, just curious.
Dave, my problems were really my problem. On one ocasion, I was playing with air breaks and set up a model 4*60 AB vs my standard 4*60. If forgot to switch back to the "good" model and when I saw 4*60 on the screen, I quit reading. What a flight. I got it back down and in one piece, but it took me an hour to get calmed down to fly again.

I've never had a shift in trim or any other issue with the 9C that I couldn't atribuite to something dumb I did. Great radio.

Don

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Old 02-04-2008, 02:40 PM
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Default RE: Futaba 9c: lost radio link to 148DP receiver

I've had my 9C since it was first released (would that be five years now?). Never had it reset any programming or trims.
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Old 02-04-2008, 04:31 PM
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Default RE: Futaba 9c: lost radio link to 148DP receiver

I have had two 9c's, one since they came out and a Super when they first came out with hundreds of flights and never experienced a problem with the trims or programming disappearing.
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Old 02-04-2008, 10:15 PM
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Default RE: Futaba 9c: lost radio link to 148DP receiver

I had a 9C for four years. Always perfect. The incident in this thread smacks of a fractured crystal. A fractured crystal will come and go sometimes.
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Old 02-05-2008, 12:08 AM
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Default RE: Futaba 9c: lost radio link to 148DP receiver

I had a simular problem with my 9CH. Two of the 4 prongs that go into the transmitter crystal pack were pushed together and going into the same hole in the pack. Anyhow I noticed that the green light on the front of the transmitter doesn't come on if it isn't sending out a signal. Only the red power light will come on. You can use this to isolate if the problem is in the transmitter or reciever. Using the Hitec synth module caused some problems because of having to take it of and on so much to switch frequencies. I use the Futaba synth Module now, I can change frequencies without removing it which is much better.
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Old 02-22-2008, 11:25 PM
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Default RE: Futaba 9c: lost radio link to 148DP receiver

Received the radio and receiver from Futaba yesterday. The repair note said no problem were found. Called Futaba service and they said the incident was more likely a radio hit.


Can I trust the radio and the receiver?

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Old 02-23-2008, 01:49 AM
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Default RE: Futaba 9c: lost radio link to 148DP receiver

Futaba is good about checking things out. I've had two reciever repaired, both working when I sent them in, but both involved in a crash. In both cases, they replaced ceramic filters.

Getting a radio hit may not be far fetched. While I was still on the buddy box, my plane suddenly lost all control and went in like a lawn dart. It was about three or four misteaks high, and neither me or my instructor could do anything but watch. The plane was lost in a creek bed for four months before parts of it were found. Any way, after looking for it for a while that day, I was back on the flight line picking up my gear and one ot the old timers was showing off his first generation computer radio. He likes to show it to anyone who will watch. It has a neat feature, a toggle switch to switch betweeen two channels. One of his two was the channel I was on. No hard evidence he shot me down, but whenever he showed up at the field, I would politely tell him that I was flying 56 and please don't switch to it. I finally cut over to 50 just so I didn't have to worry anymore.

Our field is about 1/4 mile from a local college and I've often wondered if they at times were playing with robotics and using a 72mhz radio rather than a ground frequency. We also had a highway patrol relay towere that was spilling over on our bad some years back I was told.

If you have a trainer that you are not to fond of, I would put the receiver in it and fly it for a few times before putting it in you gasser just to make sure though.

Don
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Old 02-23-2008, 06:08 PM
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Default RE: Futaba 9c: lost radio link to 148DP receiver

As Don said, test it in a more "expendable" airplane (none are really expendable...)
Spend the time to set up PCM so the throttle goes to IDLE or OFF. You might save an arm, or more.
Could your DA50 be causing noise, the receiver is picking up? Proper shielding in place?
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Old 02-23-2008, 06:27 PM
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Default RE: Futaba 9c: lost radio link to 148DP receiver

It is unlikely that DA50 was interferring, as no control each and every servo lasted 2 more minutes after the engine ran dry.

One post mentioned that the radio antenna could be disconnected from the base. Checked the antenna and it seems loosen a half turn out.

Defintely will try the receiver on a test plane.
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Old 02-24-2008, 10:00 AM
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Default RE: Futaba 9c: lost radio link to 148DP receiver

I had a 9Z that would stop transmitting intermittently. Futaba was unable to find anything wrong.....I scrapped it.

JD

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Old 02-24-2008, 11:02 AM
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Default RE: Futaba 9c: lost radio link to 148DP receiver

This is interesting. How was the problem found? Would you be able to reproduce it on the ground?

edit.

Was able to reproduce the frozen problem today with a second radio emitting FM signal. This FM radio was turned on first, then the receiver, then finally the PCM radio. Surely, the receiver has no reponse, regardless of inputs from both radios.

Still could not explain why the throttle position went to full open.

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Old 02-24-2008, 10:07 PM
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Default RE: Futaba 9c: lost radio link to 148DP receiver

My intermittant 9Z gave me an aural alarm and a message flashing on the screen...followed by the crash. It did it twice on the bench after that but I could not make it happen at will.

Isolate your problem by trying a different transmitter. If it is not the transmitter, see if you can get the problem follow the crystal: When lock out happens, leave transmitter on, replace crystal and see if it clears up. See if it will happen with new crystal. Reinstall old crystal and see if it occurs again. If so, replace the crystal. If you can isolate it to the receiver and not the crystal, throw the receiver away.

Your PCM receiver locking up with an FM transmitter on at the same (and same frequency) as the PCM transmitter, is normal. That is the "HOLD" function
of PCM.

JD
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