2.4GHz mistery glitch  
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All Forums >> Radios, Batteries, Clubhouse and more >> RC Radios, Transmitters, Receivers, Servos, gyros >> 2.4GHz mistery glitch
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2.4GHz mistery glitch - 7/14/2008 5:19:37 PM   
Beavis



Posts: 54
Joined: 10/29/2002
From: Wellesley, MA, USA
Status: offline
Hello,

I've just finished a 60-90-size plane with the spektrum AR7000 rx on a 5-cell NiCd pack, the JR X9303 2.4GHz tx, and Hitec 605BB servos on all control surfaces. Every time I test the movement of all control surfaces on the bench, after a few seconds the rudder servo slowly moves almost all the way to the right and stays there. It still responds to tx input, but will not center again. If I disconnect the rudder pushrod linkage from the servo arm and start over the test, everything is fine - the servo stays put and responds normally. However, once I connect the control linkage it will do this again. I feel no obvious tension on the linkage. The servo does not "hum" as if stressed by the linkage. I've changed to another Hitec 605BB and the scenario is the same - i.e. trouble when the linkage is on, but no problem with no linkage to the servo. I've "diagnosed" (cycled and centered) both servos tried with the JR Match Maker and they both pass with flying colors.

Can an inappropriate pushrod-control horn-servo arm linkage cause that sort of thing? If so, what should I look for on the linkage, if it does not feel tense? If not, among all the possibilities (rx, tx, etc.), can the proximity of a fiberoptics-based internet connection and router have anything to do with it (all that stuff is very close to my shop)? Any input would be greatly appreciated.

Thank you in advance,
Beavis
       Post #: 1

RE: 2.4GHz mistery glitch - 7/14/2008 5:42:53 PM   
codimasta


 

Posts: 264
Joined: 1/31/2002
From: Las Vegas, NV, USA
Status: offline 		Have you tried a different servo..in the rudder position. You could have a bad servo.....Just a thought.

Codimasta
AMA 11269

(in reply to Beavis)
       Post #: 2

RE: 2.4GHz mistery glitch - 7/14/2008 5:48:57 PM   
dirtybird


 

Posts: 2959
Joined: 1/25/2002
From: Mesa, AZ, USA
Status: offline 		If this is repeatable you have a very interesting problem. If you can repeat this with several servos the problem must be in the receiver. Try replacing the receiver and see what happens. It is conceivable that the linkage is just the right length to resonate at the frequency of your radio but that seems remote. You could check that by moving the transmitter further away and around the airplane.

(in reply to Beavis)
       Post #: 3

RE: 2.4GHz mistery glitch - 7/14/2008 6:20:22 PM   
Beavis



Posts: 54
Joined: 10/29/2002
From: Wellesley, MA, USA
Status: offline 		Thank you both.

As per the original post, I have tried a different servo, with the same result. I have not tried several servos yet.

I have moved the transmitter around, but only within the shop, which is not very big. The problem persists...

Have receivers and/or transmitters been known to lead to that type of channel-specific problem?

Thanks again.

(in reply to dirtybird)
       Post #: 4

RE: 2.4GHz mistery glitch - 7/14/2008 6:44:50 PM   
Campgems


 

Posts: 1751
Joined: 2/18/2006
From: Arroyo Grande, CA, USA
Status: offline 		swap the rudder servo cable to another channel and see what happens then. Swap an alieron or elevator to the rudder channel. That would tell you if your receiver is defective. Also, what is your pushrod material? CF? Whe you say you disconect the linkage, do you mean you pull the servo horn off or to you take the push rod out?

I'm wondering if your pushrod is and RF conductor and is interfering with the receiver, Seems to me though that if this were the case, the movements would be eratic and servos other than the rudder would be effected.

The slow movement rather than jittering leads me to believe that the problem is in the receiver and it is drifting the servo signal. This would be a great time to have an O scope so you could see what the servo signals looked like.

Don

(in reply to dirtybird)
       Post #: 5

RE: 2.4GHz mistery glitch - 7/14/2008 7:40:44 PM   
jaka


 

Posts: 4407
Joined: 12/11/2001
From: Upplands Vasby, SWEDEN
Status: offline 		Hi!
Are you sure that that battery pack is OK!?

_____________________________

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MVVS, Motul "Micro" all synthetic oil

(in reply to Beavis)
       Post #: 6

RE: 2.4GHz mistery glitch - 7/14/2008 9:45:33 PM   
Beavis



Posts: 54
Joined: 10/29/2002
From: Wellesley, MA, USA
Status: offline 		Thank you all again.

The pushrod is made of metal. There is no CF in the model. What I mean by removing the linkage is detaching the servo arm from the servo.

The battery pack is brand new, cycled 10 times by me on a digital charger. It is kept on trickle charge. I've checked the battery charge throughout this ordeal and it's always been good (above 6V), under load.

If it were a problem with the receiver, why would it work well when the linkage is not connected? It does...

I'll try the swaping of channels among the servos.

Thanks again.

(in reply to jaka)
       Post #: 7

RE: 2.4GHz mistery glitch - 7/14/2008 10:33:30 PM   
jaka


 

Posts: 4407
Joined: 12/11/2001
From: Upplands Vasby, SWEDEN
Status: offline 		Hi!
I experienced a funny thing some weeks ago when I connected a extension servo lead to my Spectrum DX-7 and suddenly the voltage dropped after that lead...! It was the extension that was bad (some decades old I think....)


_____________________________

Jan Karlsson Airracing products
MVVS, Motul "Micro" all synthetic oil

(in reply to Beavis)
       Post #: 8

RE: 2.4GHz mistery glitch - 7/15/2008 5:06:07 AM   
BuschBarber


 

Posts: 521
Joined: 1/7/2002
From: Rochester, NY, USA
Status: offline 		I have had numerous problems, such as you describe, over the years. Many times, it is a servo extension or Y harness that is defective or has dirty or loose connectors. Also, if you are running a 6v Rx pack, certain servos can misbehave or if you are using 24ga wire instead of 22ga or larger.

I have had servos Deflect, suddenly, and return to normal because there was oil from glow fuel that leaked on to the wire connectors. I have had servos Bounce, when I move the stick, and Bounce, when I return the stick to neutral. I switched from 6v to 4.8v and the problem went away. In another Bounce instance, switching the Y harness to a heavier ga wire resolved the problem.

(in reply to jaka)
       Post #: 9

RE: 2.4GHz mistery glitch - 7/15/2008 5:37:03 AM   
Wilki01


 

Posts: 68
Joined: 3/17/2007
From: Saskatoon, SK, CANADA
Status: offline 		I had a similar issue with my 9303 tx. I found the answer in the manual on the cd. Once I printed the manual, it sure made life easier. I found that in the system menu, on the 9303 every under device sel menu was default on Page A-7. I found that shutting off, all of the stuff that wasn't need for my setup cured my problem. I have it in a 1/4 scale H9 Cub with dual elevator servos and only the left elevator would behave in the same mentioned behaviour as you described. Also by turning some of the default flight modes off. Now, my sliders on the sides wouldn't affect the surfaces everytime I moved them. Just remember to disconnect the servo arms from the servo before changing the system device select modes to allow the servos to servo to the correct center. I hope this helps. I was only able to figure this out after I printed my owne manual on a brand new 9303 as the box comes with the old manual for 72mhz

Wilki

< Message edited by Wilki01 -- 7/15/2008 5:39:34 AM >

(in reply to BuschBarber)
       Post #: 10

RE: 2.4GHz mistery glitch - 7/15/2008 2:09:32 PM   
BuschBarber


 

Posts: 521
Joined: 1/7/2002
From: Rochester, NY, USA
Status: offline 		As the programming for the 9303 can be complex, that is, there are many parameters, it is necessary, sometimes, to Reset all the parameters to Factory Defaults and start again.

I just purchased the USB cable and software to Save model memories to a PC. You can Print out all the parameters and even Edit them on the PC. This is valuable if you want to Compare one model memory to another. It is also a Safe way to Backup you model memories or Transfer them to another Tx.

This is much better than DataSafe.

(in reply to Wilki01)
       Post #: 11

RE: 2.4GHz mistery glitch - 7/15/2008 6:48:25 PM   
Beavis



Posts: 54
Joined: 10/29/2002
From: Wellesley, MA, USA
Status: offline
Thank you all for the interesting and valuable insights. I was not aware of anything that you have mentioned as possible causes of this odd problem... I will explore all these possibilites, once I manage to get back to my shop. Should I be able to find eny clear cut answer to the problem, I'll post here.

Best,
Beavis

(in reply to BuschBarber)
       Post #: 12

RE: 2.4GHz mistery glitch - 7/17/2008 1:52:18 PM   
Beavis



Posts: 54
Joined: 10/29/2002
From: Wellesley, MA, USA
Status: offline
I've managed to follow up on some of what has been proposed here. First, I've inactivated all devices that were not being used in the system menu. It didn't fix the problem. Then, I played with switching the servos among different channels on the receiver. Only when the rudder servo is connected does the problem arise. That suggests that the problem is not in the receiver. I don't have 4-cell packs to try, though.

One thing I've noticed during these many trials is that the problem only shows up after I deflect the rudder all the way to the point that there is some resistance from it touching the fin at the hinge line and the servo "hums". If I remove the servo arm, recenter everything and play with the rudder "softly", i.e. without reaching any resistance point, the problem does not show up. As suggested in the original post, that points to a reaction to resistance in the linkage. However, I've never heard of that type of odd reaction from servos exposed to resistance...

So, the problem is not yet solved, nor fully diagnosed for that matter. Anyway, I thought I should offer feedback on this issue, hence this follow up.

Thank you all again for your interest and insights,
Beavis

(in reply to Beavis)
       Post #: 13

RE: 2.4GHz mistery glitch - 7/17/2008 2:33:19 PM   
Rodney



Posts: 4700
Joined: 12/8/2001
From: FL
Status: offline 		Unlikely but possibly it is a transmitter problem. If it only occures after things have been on for awhile (never happens when first turned on) it could be a heat build up problem in either the transmitter or receiver causing the problem. when you disconnected the linkage and tried again, did you leave the devices powered up just as long as when you where having the probem?

(in reply to Beavis)
       Post #: 14

RE: 2.4GHz mistery glitch - 7/17/2008 2:35:38 PM   
Bob Pastorello



Posts: 5148
Joined: 2/23/2002
From: El Reno, OK, USA
Status: offline 		If your rudder travel is set to more than 125% ATV in the 9303, it is possible the Hitec is causing the issue. On their digitals, you CANNOT run high end-point ATV settings, and the symptoms you're reporting is exactly what happens. Not saying that is your situation, but worth checking.

I make sure that NO combination of trim, sub trim, or ATV and any mixes can EVER exceed 125% on any of my airplanes, but I"m also running all 5955's and 5985's digitals.

_____________________________

Bob Pastorello www.rcaerobats.net
Learn from others...you can't live long enough to make all the mistakes yourself....

(in reply to Beavis)