HS-82MG power-on issue

[xmech2k]

I have an HS-82MG that I'm going to use for nosewheel steering in a new model, but every time I power on the rx, it turns a full 90 degrees then back to center. I'm afraid this will mess things up when installed, as it's too much movement for the linkages.

I'm using a Dx8, and the only programming done to the rudder channel is to reverse the servo. Tried it non-reversed, re-bound the tx/rx, no joy.

I plugged one of the no-name servos (that came from my destroyed Phase3 P-40 ailerons) into the rudder channel and it did not even budge when powering on. So I'm thinking it's internal to the servo?

I'm using Spektrum tx/rx. Just trying to not have to buy another servo for this plane.

Thanks for any ideas!

[Wildflyer]

In Spectrum systems, the servos will jerk to one side when you first plug in power. Some servos hardly move if at all and some like yours go quite a ways.

When the system binds, the servos go to the position the tx commands them to be.

I don't know of any way to stop this behavior, just try to give the surface enough room to move. On many of my planes all the servos jump, then center, as the system is plugged in.

Sorry, I know this is not what you were hoping for.

[xmech2k]

Thanks Wildflyer. Don't worry, I can handle the truth! I didn't think of it as part of that little servo jump like you mentioned, it's a good point. In fact, I always thought the servo jump at power up was the difference between what settings the tx/rx were at when the bind process was done, and the current setup, like different trim settings, etc. That's why I was trying to re-bind.

[A.T.]

Originally Posted by xmech2k

I have an HS-82MG that I'm going to use for nosewheel steering in a new model, but every time I power on the rx, it turns a full 90 degrees then back to center. I'm afraid this will mess things up when installed, as it's too much movement for the linkages.
I'm using a Dx8, and the only programming done to the rudder channel is to reverse the servo. Tried it non-reversed, re-bound the tx/rx, no joy.
I plugged one of the no-name servos (that came from my destroyed Phase3 P-40 ailerons) into the rudder channel and it did not even budge when powering on. So I'm thinking it's internal to the servo?
I'm using Spektrum tx/rx. Just trying to not have to buy another servo for this plane.Thanks for any ideas!

As recently answered in response to question on
Futaba Futaba 3114's Jumping on startup quote:

"It is not just a problem with using BEC, a very good explanation from "Mpx on RCMF.co.uk" with minor tweaks:
"A big glitch at switch on is typical of many analogue servos when used with microprocessor Rx.
This was seen a little bit with late 35<72MHz MHz rx but 2.4GHz rx are pretty much all microprocessor controlled so the problem has suddenly become more widespread.
What happens is that the power is applied to the servos at switch on, but the rx takes some noticeable time to boot up and during that time it does not provide a data signal to the servos.
Digital servos stay still but analogue servos have a habit of swinging a long way from wherever they are when powered up with no data, until suddenly the data signal comes from the Rx and the servo swings back to where it should be.
In the early days of 2.4 this caught out a lot of people with analogue servos on retract valves etc, at switch on the legs would retract and so on.
If it’s a behaviour that you can live with because it isn’t causing binding, retracting the u/c etc, then it isn’t a problem, if it is a problem then changing to digital servos will cure it."

Transmitter On First - Off Last

Much more under sub section
"Glitches & Jitter in Receiver, Servo & ESC - Causes and Cures"
below
"Radio Systems, Accessories, Alterations and FAQ" at
Alan's Hobby, Model & RC FAQ Web Links

Alan T.

[xmech2k]

Thanks, Alan! That makes sense. And don't worry, I'm a strict follower of tx on first/off last! One digital servo looks like it will cost about as much as the plane! So I think I may just buy another more affordable analog and hope it doesn't jump as far as this HiTech one.

Thanks also for the link. I'll be learning some new things there, too!

[xmech2k]

I was finalizing the servo installations on the plane and did one more test with this servo. I tried it in the GEAR, ELEV, and AILE plugs of the rx, and guess what? No jumping at power-up! Plug it back into rudder and it goes back to the 90 degree jump thing. Hmph!

Ah well. No biggie, I'll just pick up something at the LHS tomorrow. Coulda' been closing the fuse halves together, though.

[kyleservicetech]

Originally Posted by xmech2k

I have an HS-82MG that I'm going to use for nosewheel steering in a new model, but every time I power on the rx, it turns a full 90 degrees then back to center. I'm afraid this will mess things up when installed, as it's too much movement for the linkages.

I'm using a Dx8, and the only programming done to the rudder channel is to reverse the servo. Tried it non-reversed, re-bound the tx/rx, no joy.

I plugged one of the no-name servos (that came from my destroyed Phase3 P-40 ailerons) into the rudder channel and it did not even budge when powering on. So I'm thinking it's internal to the servo?

I'm using Spektrum tx/rx. Just trying to not have to buy another servo for this plane.

Thanks for any ideas!

H'mm
Just in case, it might be a good idea to check your transmitter for what you have programmed in for loss of signal to the receiver.

I've got the same exact thing on the flaps of one of my models, just have not taken the time to correct and re-bind.

[xmech2k]

Yes, I tried re-binding several times. It looks like just that particular servo, when plugged into the rudder channel, does that. Other servos in the rudder position won't do it. That servo in other channels won't do it.

Just an excuse to stop at the LHS today, get another servo (That was my last spare servo laying around), and window shop a little!

[kyleservicetech]

Originally Posted by xmech2k

Yes, I tried re-binding several times. It looks like just that particular servo, when plugged into the rudder channel, does that. Other servos in the rudder position won't do it. That servo in other channels won't do it.

Just an excuse to stop at the LHS today, get another servo (That was my last spare servo laying around), and window shop a little!

That's a little strange. Let us know how the new servo works out. If the original servo is the problem, I'd put a big "X" on it so it's not used in anything important.

[A.T.]

Originally Posted by xmech2k

I was finalizing the servo installations on the plane and did one more test with this servo. I tried it in the GEAR, ELEV, and AILE plugs of the rx, and guess what? No jumping at power-up! Plug it back into rudder and it goes back to the 90 degree jump thing. Hmph!
Ah well. No biggie, I'll just pick up something at the LHS tomorrow. Coulda' been closing the fuse halves together, though.

Further to post #4 above, a common servo "problem" is caused when gluing fuselage halves together
& leaving an extension lead in place without taping over the ends until after the glue has fully cured.
Fumes leave a film over the pins which does effect servo performance.
Fumes from CA (or volatile solvent) type glues often penetrate plug & socket fittings and/or damage
circuits and even damage output gear and case bearing leading to early demise of servo when a servo
has been CA'd into a wing or similar without adequate protection whilst glue dries - always wrap servo
before installation - aids easy removal at a later time.

Much more under sub sections:
"FAQ = Answers for Beginners and Advanced RC'ers"
"Glitches & Jitter in Receiver, Servo & ESC - Causes and Cures"
below
"Radio Systems, Accessories, Alterations and FAQ" at
Alan's Hobby, Model & RC FAQ Web Links

Alan T.

[xmech2k]

Thanks AT, but in this case I doubt that's the culprit. For one, the only glue I used so far is a little Gorrila and epoxy, as I haven't put the halves together yet, and I think I'll be using Gorilla for that, too.

In this case, to sum it all up, it appears that particular servo does the 90 degree jump only when plugged into the rudder channel of the rx. I plugged it into 3 other channels and it didn't do it. I also tried a different servo in that rudder plug, and it didn't do it. Got a HS65HB now, I'll give her a try tonight and give an update.

[kyleservicetech]

Originally Posted by A.T.

Further to post #4 above, a common servo "problem" is caused when gluing fuselage halves together
& leaving an extension lead in place without taping over the ends until after the glue has fully cured.
Fumes leave a film over the pins which does effect servo performance.
Fumes from CA (or volatile solvent) type glues often penetrate plug & socket fittings and/or damage
circuits and even damage output gear and case bearing leading to early demise of servo when a servo
has been CA'd into a wing or similar without adequate protection whilst glue dries - always wrap servo
before installation - aids easy removal at a later time.

Much more under sub sections:
"FAQ = Answers for Beginners and Advanced RC'ers"
"Glitches & Jitter in Receiver, Servo & ESC - Causes and Cures"
below
"Radio Systems, Accessories, Alterations and FAQ" at
Alan's Hobby, Model & RC FAQ Web Links

Alan T.

As a guy that spent 45 years fixing electronic equipment, as for me, I'll NEVER apply CA anywhere within a foot of electronic equipment. (If you can smell CA, those fumes are going all over the place.)

A while back, one wattflyer used thin CA to secure servo extension cables, then blamed the resulting radio failure and crash of the model on the radio manufacturer.

[xmech2k]

Forgot the update! The new sevo works fine. It gives just a tiny twitch at startup.