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Servo Glitch?

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olds97_lss

olds97_lss

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I know there are a million of these threads around about glitches, and I think I've read about all of them and tried everything everyone said to do. But none of it is working for me.

It's my throttle servo. For no apparent reason, it starts twitching. Sometimes to a quarter open, sometimes FWO, sometimes full brake. I've replaced the reciever, the servos, the crystals, the battery packs (I have 5) and the transmitter (thanks to bomber). Tonight I removed the metal eyelets that's on the standard maxx throttle/brake servo arm and replaced them with a plastic equivalent from HPI.

I can't tell if I'm to tired, or if the problem went away. I'll find out tomorrow when I fire it up and it takes off on me again. But it's getting to be a real pain. Last weekend, it went FWO on the lip of a ramp and did about 3 flips 20 feet in the air and of course landed on the roof. Oddly enough, nothing broke. But, hearing my brand new engine wrap wide open with no load made me cringe just the same.

Any info you guys can throw at me that I haven't tried will be greatly appreciated.
 
Oh the great t maxx get away. Man I have had my share of the sh!t happen to me. Man if you changed everything you said you did, I really couldnt tell you what to do next. Hope you figure your prob out.
 
Have you checked for outside interference?

Are you running metal servo mounts? If so, are they loose in any way? The throttle servo mounts especially?

Is your tranny case loose? I only ask, because I seem to remember you mentioning you had an aluminum one.

Be mindful of the fact that any, and I do mean any, loose metal to metal contact will generate an EM field as soon as you get that engine running and the RC starts a vibrating. So, does this problem onyl occur with engine on or off?

Double check the metal-to-metal business, one more time.

Aside from that, the servo itself could be dying. Sometimes they give little clues like this before they just up and quit.
 
The throttle servo is a week old. Hitech 625mg, steering 645mg is a few months old.

Believe me, I have checked all bolts, nuts, screws and linkage for slop. There isn't any.

It twitches when the engine is off or on. I tried a different receiver a long time ago when I had a roll cage that was causing my glitch. The roll cage is gone, but the glitch is back. I swapped out my JR receiver and transmitter for the stock crappy traxxas one that came with it. I don't have the twitch now with the engine off, will find out tomorrow when it's on.

I'm tempted to say it's the receiver. Last week, I borrowed bombers transmitter and swapped for my crystal and it did the same thing. So I don't think it's the transmitter. I swapped out my throttle servo with a different servo (jr z590M) with the same glitchy results.

I'll post when I know if it's the receiver tomorrow.

Any recommendations on a new setup? Transmitter and receiver that has a charge port on the transmitter? Also, would prefer to stay under $200. Don't need a third channel.

Thanks for the help though.
 
Are you using metal servo horns? I had an issue similar to yours that went away after switching back to plastic ones. It was weird I was getting throttle glitches but the horn was on my steering servo. May be worth looking at.

If you are using a lot of alum. on your truck such as an RX box you may want to isolate your antenna wire. Use fuel tubing to cover it from the radio to the antenna tube. Again this may be worth a try. Doing this will also help insulate the antenna wire from the power and servo wires in the radio box.

-Ed
 
I would also try a different set of crystals. With your buddies transmitter.

Just one more dang thing to check out of the million and one already.

:doh:
 
Edit--just re-read the posts and noted that you have already tried a different servo. At this point it sounds like the receiver.

You have all but removed and replaced it. I would opt for a new one and see what happens.
 
Last edited:
I would try to coil my battery lead. The interference could be coming from the lead, just wrap it around a screw driver so that the wires are coil. Sometimes battery leads can be a source of interference.
 
Originally posted by olds97_lss

It's my throttle servo. For no apparent reason, it starts twitching. Sometimes to a quarter open, sometimes FWO, sometimes full brake. I've replaced the reciever, the servos, the crystals, the battery packs (I have 5) and the transmitter (thanks to bomber). Tonight I removed the metal eyelets that's on the standard maxx throttle/brake servo arm and replaced them with a plastic equivalent from HPI.
Click to expand...
 
Note, you do not need to replace the whole radio suite (unless you want to). You can go and buy just a replacement receiver.
 
I tried swapping for a different servo as well. Problem still exists. I did try just swapping like you said as well, since the steering servo doesn't do it. With the steering servo plugged into the throttle channel, it did it too.

I think it's the reciever.

I know I can just buy a receiver. But, I was thinking of going FM as they are supposed to be less prone to glitching. This is a reciever that I bought extra. I'm using the radio since it came with my XXX-NT RTR. I've been usning the transmitter for almost 3 years now.
 
Bill brings an interesting thought into this. Perhaps the power lead is causing the problems. Do you plug the battery straight into the receiver? Or do you have a wiring harness with a switch and recharge lead attached? If the battery goes straight into the receiver (and noting you have tried several batteries), then the issue is somewhere in the physical set up of the machine. You may also have an outside interference source (radio tower, cell tower, hi power lines, etc) that may be causing the problem. If you have the wiring harness, that might be the source (good call Bill). At least it gives you one more thing to check.
 
It's wired directly into the receiver. No switch. My switch crapped out long ago and instead of putting a new one in, I opted for high quality connectors. I tried 4 different battery packs and it still does it.

With it sitting on my kitchen table, it glitches. In the field, it glitches.
 
If it's not the reciever (let us know) I would be with bll and skymaxx.

Is it possible that the physical arrangement of the wires is causing the problem?

I know for experimenting with various antennas, and lots of different frequencys, that wire in certain arrangments all by itself makes some killer antennas.

You could possibly be creating a killer am/fm antenna by the arrangment/routing of your power/servo wires.

Bill61 is right, coiling any extra wire will keep interference to a min.
Good luck, these things have been known to drive sane people nuts.
 
Sounds to me like we have eliminated just about everything on the truck. The last thing I will ask, does it do this with the transmitter on (only) or does it do it regardless of the transmitter?

If it does it regardless of transmitter being on or off, are the transmitter and receiver from the same manufacturer? If not, perhaps you have found an incompatibility issue. Though rare, they do occur, and most radio makers will list the manufacturers that their gear is not compatible with.

Other than that, you can check the wiring lay out as Lykan mentioned. You can check for a crimped wire (perhaps the throttle servo's wire is getting squeezed as it departs the receiver box or in its routing back to the servo). This is kind of a stumper.
 
Stumper... tell me about it. I have a 4 year electronic engineering degree with 2 semesters of RF and I still don't know...

The trans is a JR xr2, the receiver is a JR 122. Only does it with the transmitter on.

I have checked all wires, including the antenna. Everything appears to be good.

Stupid hobby...

I temp checked the chips on the receiver board as I was playing around with it on my table. One of the chips gets pretty hot. It doesn't appear to be an amplifier chip, more of a main processor chip.
 
Sounds to me if it only happens with the rx on, its a compatiblity/tx issue. Have you tryed a different brand of tx?

The whole wire routing thing just got me thinking in my last post "wave guide antenna", but if it only happens with the TX on, it doesn't look like it has anyhting to do with outside interference.
 

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