5955 Jittering Problem  
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All Forums >> Radios, Batteries, Clubhouse and more >> RC Radios, Transmitters, Receivers, Servos, gyros >> Radio Manufacturer Direct Support >> Hitec/MultiPlex Radios- Ask Hitec Customer Service >> 5955 Jittering Problem
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5955 Jittering Problem - 12/10/2006 11:39:06 PM   
aegis


 

Posts: 383
Joined: 11/30/2003
From: Tempe, AZ, USA
Status: offline 		I have 10 flights on a plane, and up until today the new 5955 servos worked as expected. However, when doing the ground check prior to the first flight of the day today, I noticed that one of the ailerons would jitter, sometimes, when fully deflected and also sometimes right around center. It doesn't do it all time when moving the stick throughout its full movement. The only control surface doing this is my left aileron, which has two servos. I did a range check to make sure it wasn't interference, and none of the other control surfaces, including the right aileron, exhibit the behavior.

For my RX's battery setup, I have two 1950mah 6.0V NiMHs. Each of the batteries is plugged into its own switch, and each switch is plugged into a different RX port. I have to run two aileron servos off a single channel and so am using the MPI Double Link as a wye.

I tried connecting only one left aileron servo at a time and moving the TX stick back-and-forth from full left to full right; there is no jittering. That made me think it might be a power delivery problem through the Double Link. So, I tried a different/new Double Link but got the same result. I also tried a HD 20 AWG wye and got the same jittering. (The Double Links and wye have gold plated connectors). I inserted in-line volt meters between the Double Link and servo extensions in order to see if there is significant voltage drop when applying aileron input. The voltage was 6.7V at rest and dropped to 6.65V, on both in-line meters, when moving the stick to full deflections. These were the exact same readings as the right-side aileron, which doesn't jitter at all, when measured through its Double Link. I did the same in-line voltmeter test with the 20 AWG wye instead of the Double Link; the voltage drop with the wye was just slightly more than with the Double Link. So, it doesn't appear the Double Link is the problem.

Any ideas why the problem exists only once both left-side aileron servos are connected?

Dan
       Post #: 1

RE: 5955 Jittering Problem - 12/11/2006 4:14:22 PM   
mglavin



Posts: 5200
Joined: 11/29/2001
From: Elverta, CA, USA
Status: offline 		What RX is in play?

Early release and subsequent release v1.04 servos were updated to require less control signal sinking current to allow for RX's that were uanble to provide the required current when multiple servos were ganged and driven from a single channel source.

_____________________________

Michael Glavin
RCU Community Moderator
Hitec * Multiplex Field Representative

(in reply to aegis)
       Post #: 2

RE: 5955 Jittering Problem - 12/11/2006 6:38:13 PM   
aegis


 

Posts: 383
Joined: 11/30/2003
From: Tempe, AZ, USA
Status: offline
quote:

What RX is in play?


JR R770S.

Dan

(in reply to mglavin)
       Post #: 3

RE: 5955 Jittering Problem - 12/11/2006 11:14:49 PM   
mglavin



Posts: 5200
Joined: 11/29/2001
From: Elverta, CA, USA
Status: offline 		Well it's always possible you got a servo with a problem, as the JR servos do not suffer from the sinking current issues.

_____________________________

Michael Glavin
RCU Community Moderator
Hitec * Multiplex Field Representative

(in reply to aegis)
       Post #: 4

RE: 5955 Jittering Problem - 12/11/2006 11:56:22 PM   
aegis


 

Posts: 383
Joined: 11/30/2003
From: Tempe, AZ, USA
Status: offline
quote:

Well it's always possible you got a servo with a problem, as the JR servos do not suffer from the sinking current issues.


Wouldn't the servo exhibit the jittering problem whether connected individually or jointly with the other servo on the same aileron?

Dan

(in reply to mglavin)
       Post #: 5

RE: 5955 Jittering Problem - 12/12/2006 12:49:44 AM   
mglavin



Posts: 5200
Joined: 11/29/2001
From: Elverta, CA, USA
Status: offline 		Dan,


Your problem is reminiscent of the control signal sinking current I mentioned above, and NO it only shows up when servos are ganged to a common control signal. Can you plug the suspect model halve into the latter side and see if the jittering still persists? When you tested with the wye did you have to pull the connectors out all the way back to the RX? In some cases the jittering conundrum you describe is solved by cycling the connectors due to miss-matched or dirty pins…

_____________________________

Michael Glavin
RCU Community Moderator
Hitec * Multiplex Field Representative

(in reply to aegis)
       Post #: 6

RE: 5955 Jittering Problem - 12/12/2006 5:43:55 AM   
aegis


 

Posts: 383
Joined: 11/30/2003
From: Tempe, AZ, USA
Status: offline
quote:

Can you plug the suspect model halve into the latter side and see if the jittering still persists?


My left aileron servos are normally plugged into an AUX channel (as an FYI in case it's somehow connected to the sinking current as you mentioned), and my right aileron servos are plugged into my ELEV channel. When plugging the left aileron servos, via a Double Link or wye, into the ELEV channel, the jittering is not present.

One other thing I found with a little more testing tonight ... When plugging the left aileron servos into the AUX channel as I normally do, the jittering is not there if I have only one RX switch turned on. Once I turn on both RX switches, the jittering returns. When plugging the left aileron servos into the ELEV channel, with both switches turned on, the jittering is not present.

quote:

When you tested with the wye did you have to pull the connectors out all the way back to the RX? In some cases the jittering conundrum you describe is solved by cycling the connectors due to miss-matched or dirty pins…


All the electronics are brand new. Prior to final assembly in the plane, I cycled all connectors 15 times in order to clean the contacts. As far as a miss-match, I rotated the Double Links and wye several times when doing the initial testing.

Curious to hear where I go from here.

Dan

(in reply to mglavin)
       Post #: 7

RE: 5955 Jittering Problem - 12/12/2006 1:25:40 PM   
mglavin



Posts: 5200
Joined: 11/29/2001
From: Elverta, CA, USA
Status: offline 		Any idea if the servos are early release units and or have you had them updated? If the problem is the "sinking current" this is the first time I recall an issue with JR RX's. The fact that the problem is not present when changing channel sources is suspect IMO. Are you running two RX's with single power sources or two switches into a single RX?

_____________________________

Michael Glavin
RCU Community Moderator
Hitec * Multiplex Field Representative

(in reply to aegis)
       Post #: 8

RE: 5955 Jittering Problem - 12/12/2006 4:05:39 PM   
aegis


 

Posts: 383
Joined: 11/30/2003
From: Tempe, AZ, USA
Status: offline
quote:

Any idea if the servos are early release units and or have you had them updated?


I don't know if they are early release or not. I bought them in early 2006. No, I haven't had them updated.

quote:

The fact that the problem is not present when changing channel sources is suspect IMO.


Not sure what you mean by "suspect." Does it make you think that it is a sinking current issue, or that it isn't?

When experiencing the sinking current issue you've talked about, is it "normal" to have a problem on one channel and not another?

quote:

Are you running two RX's with single power sources or two switches into a single RX?


Single RX with two switches/batteries.

Dan


(in reply to mglavin)
       Post #: 9

RE: 5955 Jittering Problem - 12/12/2006 8:02:50 PM   
aegis


 

Posts: 383
Joined: 11/30/2003
From: Tempe, AZ, USA
Status: offline 		Michael,

Here's a little bit more info in case it helps. I tried plugging the right aileron servos into the AUX channel to see if the jittering would appear as it does with the left-side ailerons. It doesn't ....

Just to have things in one post, here's a summary of the configurations I've tried and the results -

Only one RX battery switch turned on and left-side aileron servos plugged into either the AUX channel or the ELEV channel

  • No jittering


Both RX battery switches turned on

  • Jittering does not occur if only one left-side aileron servo is plugged in to the AUX channel
  • Jittering does not occur when both left-side aileron servos are plugged in to ELEV channel
  • Jittering does not occur if both right-side aileron servos are plugged in to the same AUX channel
  • Jittering occurs when both left-side aileron servos are plugged in to AUX channel


So, the only time I get jittering is when both switches are turned on and both of the left-side aileron servos are plugged into the AUX channel.

If it's a servo problem, wouldn't the left-side servos jitter whether plugged in to either the AUX or ELEV channels? On the other hand, if it's an RX problem, wouldn't both the left-side and right-side servos jitter when plugged into the AUX channel? (Not trying to argue with, just asking).

Dan

(in reply to aegis)
       Post #: 10

RE: 5955 Jittering Problem - 12/13/2006 4:02:53 PM   
mglavin



Posts: 5200
Joined: 11/29/2001
From: Elverta, CA, USA
Status: offline 		Dan,

If the servos are an the problem the RX is NOT providing the sinking current for same. I suspect your RX is the problem for whatever reason as it functions on some channels and not others. Please try another RX to eliminate this variable.

You might also consider sending the servos to Hitec Service to eliminate the question of updates and possible servo anomalies. In the event of the servos needing updates this may very well solve your problem, but also indicates the RX is suspect IMO as I noted previously JR RX’s do not have an issue with sinking current.

_____________________________

Michael Glavin
RCU Community Moderator
Hitec * Multiplex Field Representative

(in reply to aegis)
       Post #: 11

RE: 5955 Jittering Problem - 12/16/2006 2:01:23 AM   
aegis


 

Posts: 383
Joined: 11/30/2003
From: Tempe, AZ, USA
Status: offline
quote:

I suspect your RX is the problem for whatever reason as it functions on some channels and not others. Please try another RX to eliminate this variable.


I borrowed a JR R720 RX. The jittering is still there. As with the original RX, the jittering appears only if the left-side aileron servos are plugged in to the AUX 1 channel and both RX battery switches are turned on. If only one of the batteries is turned on, there is no jittering. If plugging the left-side servos in to the ELEV channel, with both batteries turned on, they are rock solid. As with the original RX, there is no jittering of the right-side aileron servos if plugging them in to the AUX 1 channel.

Dan

(in reply to mglavin)
       Post #: 12

RE: 5955 Jittering Problem - 12/16/2006 3:01:54 AM   
mglavin



Posts: 5200
Joined: 11/29/2001
From: Elverta, CA, USA
Status: offline 		Boy this a good one...

At this juncture I'd suggest sending the servos to Hitec Service for the update and a look see.

_____________________________

Michael Glavin
RCU Community Moderator
Hitec * Multiplex Field Representative

(in reply to aegis)
       Post #: 13

RE: 5955 Jittering Problem - 12/18/2006 5:42:21 PM   
aegis


 

Posts: 383
Joined: 11/30/2003
From: Tempe, AZ, USA
Status: offline 		Latest update - Over the weekend I was messing around with this some more and in the process I ran my batteries down to 6.5V. At that level, there was no oscillation (with both RX batteries turned on). I charged up the batteries and at a full charge (7.0V) the oscillation is back. Could the problem have something to do with running the servos over 6.0V? Prior to buying them I called