excessively jumpy 7955
 

I just upgraded all my radio gear to lipo, i bought the new airtronics mt4, and a new 7955 for my throttle, (i already had one for my steering). i know all digital servos twitch a little to find center, but i noticed today that my throttle servo is excessively jumpy. Like it would literally move instead of twitch.

I programmed one of my switches to offset my throttle (to keep it open to refuel) and i am pretty sure it does it less with my throttle offset off, but it still does it.

so, what is happening? Some other things worth mentioning, i have 3 bands to pull the throttle shut. I wouldn't think it would be too hard on the servo, it supposed to have almost 400 oz of torque, and besides i ran the same thing on my 7985 with no problems. I also am breaking in a new motor so i am using the heat gun quite a bit and i am doing my best to keep it away from the battery and again i have done this many times before with no issue.

Any ideas? Is there a setting on my radio that i need to change or is this normal?

Are you running a regulator? The 7955 isn't a high voltage servo, so if your running a LiPo to your reciever the servos are getting 7.4 volts as compared to the 6.0 volts max that the servo's require can cause the servo to do that and damage it at the same time. You can also check the end point adjustments (EPA) and adjust the distance the servo travels back and forth on the throttle.

HV on the 7955 is ok, at least that is what everyone has told me including hitec. Once I took the throttle offset off it is back to its normal twitching

Your incorect the 7955 are lipo ready :confused:

Posting is hard to understand but check your linkages make sure theirs no binding. If you have a spare battery change see if it makes a difference.

If its a glitching issue some people run caps.

I am done for the day so I will diagnose the issue. Its really just a little more twitching then I am used to.

And excuse my ignorance, but what is running a "cap" mean?

http://www3.towerhobbies.com/cgi-bin...&I=LXNRE0&P=ML

A glitch buster. Keeps voltage steady. Also, a Hitec servo programmer may be a useful tool where you can adjust the deadband,reslution,and EPA of the servo among other things.

cool thanks!

I really think i was just being overly cautious. I have tried it with nihm batteries with the same result. Also, it easier to notice on the trottle because of the big ass servo horn.

It really is just trying to center itself.

But, that does look like a usefull tool. I hate dead zones, put my car on setup station and there is usually almost always a 1 degree dead zone in my steering. Aggravating.

Not sure what you run for a tx, but Futaba has a setting for normal or digital servos. Running a digital servo on normal can burn it out.
The servo programmer is a handy tool to have. The PC model is only around $20. I use it to open up the dead band on the 7955's I have in my scale rigs. Stops the buzzing of it tring to center ALL the time.

It's only rated on the Hitec website for 4.8v and 6.0v nowhere does it say it can run on 7.4v. Couldn't find it in my manual either but it does say if the servo is run on a higher than the recommended voltages it voids the warranty, just saying it can and probably will reduce the life of the servo. I've had mine for a while about 1 1/2 years and seen guys not run a regulator with the 7955 and burn them out after 2-3 races and Hitec won't replace because it burns out the board and the motor because they aren't designed for 7.4v. Do what you want and replace your servos 2-3 times a year, not my problem just yours.:rolleyes:

:lol:

they run robots at 8.4 with 7955's idiot.

oh and scroll down to the fifth post in this link.

http://www.rctech.net/forum/ask-hite...regulator.html

He states it's not officially rated for a 2s 7.4 volt battery, just think about it you MORON if it gets roasted by your 7.4 volts they won't replace it because you are running an unofficial voltage to it and when you send it in they will see that it was electrical damage that wouldn't happen from 6.0 volts. I have several racing friends that ran there 7955's on 7.4v and went to a high voltage servo after toasting the 7955 and hitec refused to replace it. I guess you have more money than brains, IDIOT.

6 volt nimh packs run at over 7.2 volts when they are freshly charged. Life 6.6volt batteries peak at over 7.8 volts when they are freshly charged. The 7955 can and will handle unregulated 2s Lipo packs that hit around 8.2 volts freshly charged. I have 6 7955's and they have been running with unregulated Lipos without an issue now for well over a year using unregulated Lipo's. Not a single problem with any of them.

Your more likely to burn out a Hitec servo from not setting the EPA's and failsafes properly than you are from burning one out from a bit more voltage.


WHats funny is everybody has "friends" who have a problem with their gear when people mention it in posts. Many times those "friends" dont even exist. :lol: Who is to say your "friend" specifically burnt it out due to high voltage, and not to improper settings, abuse, or any other potential issue. For all I know this "friend" could have jammed on an incorrect splined servo saver on his 7955 and had a poorly setup steering system with major binding problems from debris and a poor build and overthrow of the servo itself.

"Friends don't let friends post about their friend's own potential problems" :lol:

Hitec generally has a no questions asked repair/exchange policy, whether the servo was abused or not. As long as you got proof of purchase within a 3 year period of time then they take care of you. All the 7 series servos are fully rebuildable, every single part. And its quite cheap to repair/rebuild em too. A $150 dollar servo generally has less than 10-15 bucks worth of actual parts wholesale.

U MAD?

No I'm not mad! A good debate keeps the blood pumping. And I guess I am an IDIOT and I am making a public apology to Dreaux for calling him a moron and an idiot with more money than brains. The guys from Hitec got back to me and said it was fine to run the 7995tg on 7.4v with no problems and no void to the warranty, in my defense I always read the manual and apparently the newer manuals don't say not to run it on 7.4v but mine did and the friend I was talking about lied about sending it in to Hitec for repair because he said it sounded better than saying he went out and paid $120 to replace it. I am sorry and hopefully it won't happen again.

Did you ever figure out what was making the servo jumpy?