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Odd radio glitch, please help...

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Old 07-03-2004, 05:26 PM
  #1  
bobinma
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Default Odd radio glitch, please help...

I have a H9 Edge 540, with a Saito 180, dual elevator servos in tail, and the rudder is pull-pull mounted in the stock location. Radio gear is Futaba S9150's on elevator and ailerons, S9451 on rudder, and S3001 on throttle. Receivers is R127DF running on 2, 5 cell packs plugged directly into the reciever on seperate switch harnesses. The same transmitter, a 9CHP, has no problems with 5 other models in memory, so that eliminates that possibilty. I've used the channel 34 for 15 years at the same field with no interference, and never detect any problems with all my other airplanes that share the same channel.
My glitch is rudder and throttle. At random intervals, and for about 1 second duration, the throttle increases and the rudder kicks right.
I have tried swapping receivers; the problem stayed with the Edge and the recipient plane flew normal. Re-routing the antenna 90 degrees out along the wing didn't help.
I suspect some RF interference, because the glitch only hits the servos in the cockpit area of the plane, and only with the engine running.
I searched for metal to metal contact, and found my remote headlock was sagging and touching the cylinder head cooling fins.
This is the one I am using,

My theory was that its causing some noise at specific RPMs, and causing the servos to twitch. When the RPMs increases, the noise frequency changes, and the effect stops. The metal pushrod for the throttle may be a factor here, possible directing the effect towards the 2 servos in the cabin.
I took some rubber tubing and made a donut to isolate the headlock from the cylinder head.
The outcome? Well, 90% of the effect was eliminated. I flew 3, 12 minute flights with absolutely no problems, however, on the last flight, I detected some twitches on the rudder.
I am now completely frustrated and don't know what to check next. I'll change my metal throttle to a nyrod, but I don't have much confidence in that fix.
Any inputs from anyone??
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Old 07-04-2004, 03:48 PM
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Default RE: Odd radio glitch, please help...

Check the servo connectors. Plug ang unplug them several times.
It may not help but whenever I have had problems with servos it usually is the connectors. And it is a simple thing to check.
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Old 07-04-2004, 11:42 PM
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Default RE: Odd radio glitch, please help...

I'll do that. I flew it today and it still hits on the rudder servo. I have owned dozens of planes and heli's over the years, and this is the nicest, most expensive machine I have ever had. I can't relax and really get into this plane with these issues, it makes for alot of stress. I ordered a new S9451 for the rudder, maybe I got a bum servo. I'll send it to Futaba and see what they say. If the new rudder servo doesnt cure it, I'll swap throttle servos and change the metal pushrod to Nyrod. After that, I have no idea what I could try next.
The *only* other thing it might possibly be is this-keep in mind I'm grasping at straws here....
I crossed my rudder pull-pull cables to make beter geometry where the cables exit the fuse inthe rear, is it possible the cables rubbing on each other are making some electronic noise? They are just the standard Dubro cables from their pull pull setup....
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Old 07-05-2004, 12:29 AM
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Default RE: Odd radio glitch, please help...

Try narrowing down the problem further:

Eliminate the possibility it's the TX by trying another Tx.

If the problem persists, you're left with: servo, RF from onboard glow, metal pushrod, or pull-pull cables.

Switch the plugs on rudder and elevator. Rudder now on 2, El on 4.

If the problem persists on ch 4 (now elevator), eliminate the servo, it's probably RF.

If the problem persists on Rudder (now ch 2), eliminate RF, it's probably the servo

BTW, I haven't tried pull-pull yet, is it OK to have the cables rubbing up against each other?
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Old 07-05-2004, 07:43 AM
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Default RE: Odd radio glitch, please help...

That's a good way to go patternwannabe. At what point is a voltage regulator needed too? I really don't know that answer, but somewhere in that 6-volt(5-cell) pack range I think I've heard of some running regulators/matchboxes.
I have that same Edge w/Moki 1.80. I run a single 4.8v(1400mh) pack on a R127FM Rx, with no prob...matter of fact, I have same set-up in 3 large planes. Good luck finding it though, and be safe.
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Old 07-06-2004, 11:07 AM
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Default RE: Odd radio glitch, please help...

most rudder pull/pull cables are coated in plastic....make sure your's are.

if you have the 180 saito with a metal throttle arm (earlier version) and you are using a metal clevis on it ...this is your problem. change to either a nylon clevis or ball link.
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Old 07-06-2004, 11:19 AM
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Default RE: Odd radio glitch, please help...

I would add 2 JACCIO 5.1v regulators. This will provide consistant servo speed as the batteries run down as well as lower the voltage to the servos.
IMO, 6v is too high.
I use these regulators with 6v and Futaba servos and the servos work just fine.
Replace the metal throttle pushrod too.

Regards

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Old 07-06-2004, 07:49 PM
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Default RE: Odd radio glitch, please help...

Well, I can eliminate the possibility it's the X-mitter, I use the same one on a Concept 60, GWS Pico Stick, H9 Twist, a foamy edge, and a 120 Stinger with a 31cc Ryobi. All of these models are rock solid. My Saito has the plastic arm, and I have a plastic clevis on it as well.
I have a new S9451 on the way, so I'll swap that out and eliminate the possibility it's the servo. After that, I'll swap the throttle servo and ditch the metal pushrod. 3rd step will be to get ahold of some 4.8 cell packs and try that. 4th step, sell the plane.
I'll keep you informed.
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Old 07-07-2004, 12:37 AM
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Default RE: Odd radio glitch, please help...

Just for kicks try a single 4 cell on the reciever. I have had 5 cell batts cause glitches fresh off the charger, and went away after 4 or 5 minutes.
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Old 07-11-2004, 04:45 PM
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Default RE: Odd radio glitch, please help...

Well, I replaced the S9451 with another one, and now I have no problems. I flew 3, 10-12 minute flights today and my Edge is stable as a rock. It was a good day and what little wind we had was right down the runway. I declare this problem fixed.
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Old 07-14-2004, 09:45 AM
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Default RE: Odd radio glitch, please help...

if the headlock is connected to an onboard glow unit you may have found your problem right there. they dont make really good connections and the vibration (metal to metal contact) at such high rpms will cause it to send an electrical signal back through the wire and if your onboard glow is not photo-optically isolated, it goes straight to your receiver. i had the same probem, but i got lockout. i have pcm
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Old 07-16-2004, 06:36 PM
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Default RE: Odd radio glitch, please help...

nope, no on-board glow, just a remote headlock so I didn't have have a gaping hole in the side of my cowl
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Old 07-30-2004, 07:05 PM
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Default RE: Odd radio glitch, please help...

It's BAAACCKK!
Well, I guess I called it good prematurely.
I'm getting to the point where I just don't care anymore if this glitch causes the plane to be destroyed. Obviously, I don't want to injure anyone in the process though!
I'm really at my wit's end here.
As a recap...
Switched recievers. (the reciever I removed works fine in recepient aircraft)
Since same tranny works with 5 other models flawlessly, I think I can safely rule that out.
Relocated antenna routing several times, including stretching it directly out towards wing tip.
Checked for and eliminated all possible metal-metal contact.
Swapped out rudder servo.
No onboard glow, just a remote headlock.

Here's what's I'm going to try next.
The aileron servo extension wires pass close to the rudder servo, and maybe they are generating some random noise.
I'm going to try twisting them, and re-routing them as far away from the rudder servo as I can.
Updates to follow...
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Old 07-30-2004, 11:10 PM
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Default RE: Odd radio glitch, please help...

wait. here are a few suggestions. 1st of all, even without the remote glow, the headlock style glow clips do vibrate against the plug a bit and if severe enough will cause a harmonic electrical frequency to run down the wire. try putting a 2mm or 2-56 nut in between the plug tip and the brass contact for the plug. it should self center and it will force the spring up farther, meaning greater force against the plug meaning less rubbing hopefully. also, if you have any long servo extensions, try putting chokes on them or if you dont want to cut up the wire and add the weight, hold one plug end tight and twist the wire until it does not want to twist any more (dont force it though because those wires arent that robust) and let go. it shouldstay twisted a little bit. it will not be tight, but that is okay. the idea is for it each wire to cancel out any frequency running down it by twisting around itself. you could also disconnect the wires and braid them and put them back in the right order and they will cancel eachother out and it does not look as wierd.
it is also possible that your engine is producing a wierd frequency. try changing to a different glow plug, make sure all the bolts are tight, the engine mount bolts and the bolts that secure the mount to the firewall. also check your landing gear if it is metal.

if nothing else works, break it down to it's simplest form. take everything out except the throttle servo, the engine and battery pack. make sure it works and does not glitch WITH THE ENGINE RUNNING. (i assume the problem occurs when the engine is running. if it occurs when it is off, you can rule out that possiblity). if all is good, install another component, but only go 1 component at a time. make sure everything works before you put in another component. you will either find that after you put a certain component in it will cause problems, or that after you have put everything back in you dont get the glitch. if you are getting glitches before you put any components in (just the rx, battery, throttle servo and engine) than i would try disconnecting the throttle servo from the engine, but keep it connected at the receiver. if it still glitches, your problem is your engine (it cant be your antenna or rx because you have moved them and changed them and stuff) and if it stop glitching, it is the connection between your throttle servo and your engine
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