View Full Version : Servo twitching

2002.01.16, 10:07 AM
Hi All,

I would like to know if anyone else has this problem - a constantly twitching servo for steering? It has really started to annoy me as it was only a very minor problem when I first started driving the car around, but after leaving it for a week and a bit - I drove it just then and realised that the servo arms were twitching like mad and I couldn't even steer straight~!!!!!!! Can someone please help me out. I am not holding anything that emits radiation such as mobile phone which would affect it's reception.



2002.01.16, 12:56 PM
Found this. Haven't tried. Any comments? Q&A #2 http://www.cyberduk.com/tech_tips_and_tricks.htm

2002.01.16, 01:05 PM
There is something else you can check. Open the servo cover and apply a VERY LITTLE ammount of clear silicone sealant to the top of the steering potentiometer to make sure it doesn't move around. DO NOT apply anything to perminantly glue it down or you will regret it when it comes time to replace a servo gear.

The potentiometer tells the servo where the center is, and if the potentiometer is loose, it will cause the servo to think it is out of adjustment and the electronics will cause the servo to find center again, essentially it looks like it twitches as it goes one step to the left or right.


2002.01.16, 02:22 PM
Many threads on this... A LOT! search for twitching in search page...


The capacitor is only to reduce the noise the motor makes, if yer servo twitches while car is not applying the throttle... then the capacitor will not help.... but it does sort of help while the car is rolling forward if done right.. the capacitor I added, kinda made it worse.. but mine is bad example because my elec. board in my Mini-Z was partialyfried, antenna touched the battery terminals, wich might be what happen in yours or something similar. Depends how bad it is.

2002.01.16, 02:52 PM

Good catch there.
That website in excellent..

Keep up the faith..


2002.01.16, 02:59 PM
change the batteries on the radio control.... that worked for me.... unless you did something to fry the esc....

2002.01.16, 03:04 PM
Hi again people,

I'm sorry I didn't clearly state my situation with the servo for the steering. The car when I don't even go twitches at the steering and has sometimes cause me spin-outs when I'm going. I have always run a fresh set of batteries so hence I'm a little confused as to what is going on with my Mini Z since it doesn't happen on my Colt Mini.

Need help again people... :(


2002.01.16, 03:25 PM
This is my test;

Put radio on table - powered on.

Turn car on... center the steering and throttle adjustments...

See how far you can walk away from the radio with out the car going OBVIOUSLY bonkers... lots of beeping and squirming...

This is your range... if its less then 10 or so feet.. you some how fried your circut board.. it only takes a fraction of a nano second, and like mine it functions, but the range is VERY limited and I know I fried mine for like 1/10th of a second antenna touched battery terminals.

If its less then 30 days old and you have the reciept, mail it to hobbico (Kyoshos USA repair service center). They will just replace the circuit board and send it back.

Places like D****** claim they can fix the car but they are in Hong Kong, and not worth sending the parts there, and they also refuse to share how to fix it.. (i've asked) cuz I guess they think thats bad for business, better to make the money then help ppl with their Z... Thus I probly wont buy anything from them.

2002.01.16, 03:32 PM
Hi All and Drac (thanks for your reply),

I honestly doubt I have fried my circuit board due to the fact that I have run my Mini Z in total of less than an hour, and I always remove the battery imediately as soon as I turn it off. So I don't possibly know how I would have fried the battery board. There must be some radio interefence with that channel I'm using (channel 6). The car twitches with the remote 2cm's away from the antenna, so I guess there has to be something more sinister than what you've described. Anyone with ideas??? Russ, Mini Z, Mondo, D's Nutz????

Thanks Peoples - really appreciate it~!;)

2002.01.16, 03:40 PM
Also if its itty bitty twitching, thats normal.... the car will twitch. its constantly re-centering. Try turning the controll all the way to one side, and see if that still jerks, it should still give itty bitty jerks as it tries to hold that angle.

If it ever jerks all the way side to side then thats definate interferance, from a computer, refrigerator speekers anything that is not sheilded properly. You culd try disconnecting yer motor and see if it stops (might not be totaly center throttle)... but I doubt it will.

A fried reciever (like mine) the mini-z works fine.. upto a given range, but the fact that its fried prevents it from being able to filter out the noise... that bottom dial I think is some sort of squelch like on a CB -- also make sure your no were near a CB, cuz this is the same frequencies as CB radios use, or rather close to them... for example a frequency half way between 5 and 6 is a CB channel.. and 6 between 6 and 7 is too, same with every mini-z frequency. these channels are used in USA CAN. and some areas of UK> but not in japan so they get to use them in their Mini-Z... this is why most ppl in US etc.. have interferance problems with Mini-Z's...

You could also try a longer antenna... wich worked for mine before I fried my reciever...

It could also fry itself by poor manufacturing there are a few places on the circut board were solder points are very close to each other and there is enough bare wire to reach over to them if the wires were bent in the right direction... you never know it might actualy be fried the first time u turned it on...

You culd tr

2002.01.16, 04:27 PM

I can't add much, Draconious is providing all the correct troubleshooting and diagnostic proceedures..

Follow Drac's instructions and I am sure you'll draw your conclusions. Fortunately I have never suffered any of these problems or symptoms.

One thing no-one has suggested is: Ensure the TX antenna is screwed down firmly..


2002.01.16, 04:30 PM
Thanks Drac and Mondo,

I'm trying what Drac said to do at the moment and I'm testing it - thanks guys... Really appreciate the help.


2002.01.16, 09:22 PM
Little known fact that I found hillarious... I have seen many places say to screw the TX antenna down nice and tight.

Well.... with the TX the Mini-Z comes with , this does not matter, heck you dont even need to screw it down!!!

Why!? cuz the screw has no wire on it! the way it contacts to the antenna is it just rests against 2 metal tabs wich are intern screwed down to the circiuit board in the TX.

I have taken mine apart and seen, I knew I should ahve taken a clsoe up photo of it, dont want to take the plastic apart again, would be the 5th time, those screw threads starting to strip ;)

I have when it was apart last, in hopes of improving the braodcast signal run a stainless steel wire, same one I use for my replacment antennas.. I screwed this into the antenna screw, and the screw that holds the little contact onto the circuit board... this didnt do diddle squat.. its still a bad broadcast. :) - or at least my Mini-Z still cant filter out the background radio noise...

Just had to add that, since I forgot long long ago when I hit make new thread and forgot what I was going to type... hehe. Thnx for the reminder Mondo :).

2002.01.17, 03:35 AM

I've never seen it mentioned, perhaps my "Braille Terminal" needs an upgrade, or my guide dog needs to eat more carrots :D


2002.01.22, 12:05 PM
This may shed some light…

I got a 911 for Xmas. It worked fine for 2 weeks. I used it indoors on hardwood for 10 days and then converted our concrete-floored garage into a track. Within 3 days the steering was twitching to the point it was undrivable. Like almost everyone else, I assumed it was interference. I turned EVERYTHING in the house off. No help. I took the car apart and in the process fried the ESC. I sent the car back and got VERY lucky as the retailer replaced it with a CLK.

A week after the CLK arrived ANOTHER one arrived. The retailer double shipped the order! Yes, I am sending it back. (what would I do with 2 CLKs AND a Mugen NSX?) The cool part (for this discussion) is that is EXACTLY the same car, same freq. etc.
I ran the first CLK for 2 weeks in the same garage. I use foam pipe wrap for the track etc and this time I was really careful. No hard bangs etc. Sadly, the steering now twitches madly (after approx. 4 hours of run time), just like the 911.

I am starting to read the HPI adds…

I am an engineer and unable to walk away from this so I opened the second CLK box (carefully!). I put fresh batteries in BOTH chassis and turned on ONE Tx (also with fresh batteries). The “old” CLK twitches and the new one DOES NOT. Guess what, folks? IT IS NOT AN INTERFERENCE ISSUE! The new CLK is ROCK SOLID, the old CLK twitches for 2 minutes then stops for 2 minutes etc. This is with the motor off and NO ANTENNA on the new CLK.

Analysis: Both the 911 and the “old” CLK get a fine coating of dust after and hour in the garage and I am now thinking this may be the problem. I pulled the steering servo but did not disassemble it. I blew on it as best I could and this had a noticeable (positive) affect. For me, the next step is to disassemble the steering servo and blow it out with canned air.

I think the common signs are:
A couple of weeks of problem free running
Dirt/dust build up
Twitching servo when standing still
No noticeable loss of range

2002.01.22, 12:08 PM
so dust is the problem?

2002.01.22, 12:11 PM

Firstly, welcome to the Mini-ZRacer.com forums. It's refreshing to see a first posting that is so informative! Good catch there, I look forward to more of your postings..

I'll keep that in mind. I don't experience any twitching with any of my Mini-Z's.
But, should they start... I'll follow your lead :)


2002.01.22, 02:29 PM
Assuming it is a dust/dirt issue maybe we could get some input from other drivers.

We need input from both "twitchers" and "non-twitchers".

Consider these questions:

1) Do you have the "twitch" problem (defined as: car at rest, close to Tx, steering twitches up to 25% of full servo throw, transient). Are you sure the electronics are not fried?

2) What track surface do you run on? Concrete, carpet, wood, tar paper etc.

3) Is it dusty/dirty? Indoors or out? Do you see a film of dust on the car at the end of a session?

4) How long have you run the car (approx. hours).

5) For those with "twitch" problems: Did it start some time after you started running the car or right away?

Perhaps we can spot a pattern...