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  1. #1
    RC Racer
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    Truck Running Erratic

    5000 NiMH running the 775 conversion

    My truck starts running erratic after running it for 20 minutes or so. It has lost a little of its punch by this time, but still is running pretty fast. It then sticks on acceleration and won't stop until I catch it and turn it off. I got this truck on trade in for my old T-Maxx, so I have still learning the ins and outs of out. I have never had this issue on my Pede.

    Any thoughts? Is this normal when a NiMH drains? I have tried searches on this subject, but haven't been able to find anything.

    Thanks!!

  2. #2
    RC Turnbuckle Jr.
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    What radio is it running- 2.4ghz ( brand? ) or an AM / FM radio of some sort ( old crystal radio )?

    If it's AM / FM, there's your issue pretty much, most likely interference of some sort, though it may be an overheating issue- what are the esc and motor temps?

    If its a 2.4ghz radio, then it sounds like either major interference or the tx & rx need rebinding.

    Nothing to do with the main batts though, you will always have full control even when the truck grinds to a snails pace ( which you shouldn't do anyway as it is bad for the batts ). I'd be looking over the electronics and checking for damaged or loose wiring, check the motor has the little ceramic capacitors soldered to the terminals and can, and make sure the tx batts are fresh too.
    Keeping the Mods busy is my specialty...

  3. #3
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    Great question. Yes, I am running the AM radio. Is there a reason why I would have interference with the Revo and not my pede? Temps on the motor were around 145 deg at the end of the run. I did not check the temp on the esc.

    I didn't think it was the batteries, but I wanted to make sure as these are my first NiMH batteries as I am still running Nicad on my pede.

    The truck runs very tight for at least 20-25 minutes and then it starts acting up at the point. Maybe it is overheating. Cutting a whole in the windshield should help keep it cooler, correct? Is there anything else I should do to help keep it cool?

  4. #4
    RC Turnbuckle Jr.
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    Fan on the esc may help, depends if it was running hot or not- 145F on the motor isn't bad though really. Taking out the grill and windshield and replacing with mesh can help a fair bit for sure.

    Did you check the motor to see if it has the little caps soldered to it- they are important when running an AM radio. You could also try a ferrite ring on the signal wire from esc to rx, sometimes helps, as does routing the wires away from the motor as much as possible. As for why it doesn't happen on the pede ( assuming thats AM too ), good question- you could try swapping crystals if they are compatible, otherwise an upgrade to a cheap 2.4ghz radio usually does the trick- check hobbypartz for their cheap GT2 & GT3b radios, highly recommended around here and many other forums.
    Keeping the Mods busy is my specialty...

  5. #5
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    OK...checked for the caps and they are both on there. I will check the temp on the esc that next time that I run the truck.

    I've not heard of the ferrite ring before. Please explain. I will try changing crystals, but one again this only is happening once the battery has drained down after 20+ minutes of running. The truck then starts running really fast. I can still steer, but can't get it to stop until I either flip it over and get it over to me, so I can shut if down.

  6. #6
    RC Turnbuckle Jr.
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    Ta-da:



    It is essentially just a small donut shaped magnet which you wind the escs rx lead through a few times before it plugs into the rx, the magnetic field helps to strangle any interference the lead picks up between the esc and rx. Same deal with braiding BL motor wires, helps to collapse the magnetic field that is induced in the wires, so there is less interference with the radio signal.

    I take it the 775 motor has the metal sleeve over it like normal though, hasn't been removed?

    Not really got any more ideas to help this really, if temps and wiring/wire routing are all sound then an upgrade to a 2.4ghz radio is about the last resort..
    Keeping the Mods busy is my specialty...

  7. #7
    RC Racer
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    Yeah the can is fine and doesn't appear to have been tampered with.

    The hobby shop that I got it at is about 45 minutes away and I will check with them also to see what their thoughts are.

    Thanks for your help.

  8. #8
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    It sounds like a problem with the radio or ESC to me, what shape are thd Tx batteries in just out of curiousity?
    Aw, Biscuits!

  9. #9
    RC Turnbuckle Jr.
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    Quote Originally Posted by offroadin View Post

    The hobby shop that I got it at is about 45 minutes away and I will check with them also to see what their thoughts are.
    For the lulz I would like to see what they have to say, if anything much; if they start making noises about spending $$$ to 'fix' the issue, you should just walk away.
    Keeping the Mods busy is my specialty...

  10. #10
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    Quote Originally Posted by bjoehandley View Post
    It sounds like a problem with the radio or ESC to me, what shape are the Tx batteries in just out of curiousity?
    TX batteries are fully charged!! To me it sounds like a radio or ESC issue also, but I wasn't 100% positive.
    Last edited by offroadin; 10-10-2011 at 03:11 PM.

  11. #11
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    Quote Originally Posted by ArmyofDarkness View Post
    For the lulz I would like to see what they have to say, if anything much; if they start making noises about spending $$$ to 'fix' the issue, you should just walk away.
    I'm going to try to get over there on Wednesday to see what they say.

  12. #12
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    Quote Originally Posted by offroadin View Post
    TX batteries are fully charged!! To me it sounds like a radio or ESC issue also, but I wasn't 100% positive.
    Have you had the change to try a different radio equipment or at least different crystals yet then? I've been running the 775 since March of '09 and haven't run into this issue with my Traxxas Link radios or the Futaba 3pm Synthesized FM that it replaced. I have had issues with my truck slowly running backwards for no reason on my 2 channel Link radio, but not that issue.

    Quote Originally Posted by ArmyofDarkness View Post
    I take it the 775 motor has the metal sleeve over it like normal though, hasn't been removed?
    I just put a new 775 without that collar on mine and didn't have that issue when out bashing with friends Friday night, so I doubt that is it.
    Last edited by bjoehandley; 10-10-2011 at 03:48 PM.
    Aw, Biscuits!

  13. #13
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    I had a runaway Erevo once....it was controlled by a 27 Mhz RX/TX and Ferrite ring was in my case essential to avoid runaways .
    As well as solderings and all connections must be intact.
    But without a ferrite ring,,, suddenly the truck would get out of my control.....dont know if it helps you any :-)
    Slightly Addicted

  14. #14
    RC Racer
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    OK, I just got back from the LHS and I found out another piece of info. The vehicle is equipped with the Novak Smart Stop Auto-Stop module. The LHS believes that it had some how had got out of sequence in a manner that was causing the truck to lock into full throttle when the batteries started draining instead of shutting down. They showed me how to unhook this and hook it up as it came from the factory. I ran the truck for around 15 or so minutes and it doesn't seem to be going full throttle stuck. I am going to try it again over the weekend as we are expecting rain the next few days. I will let you know how it performs.

    Let me know if this makes any sense or if they were blowing me full of hot air!

    Thanks!!

  15. #15
    RC Racer
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    BTW, I forgot to look at the LHS for the ferrite ring. Is that where I find one?

  16. #16
    RC Turnbuckle Jr.
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    Google is where I found them, I doubt your LHS would carry them really, more of an electronics store kinda thing ( radio shack & such ).

    If we had known there was a smartstop involved, that would have been the first thing I'd have said to look at or remove to trouble shoot the issue...
    Keeping the Mods busy is my specialty...

  17. #17
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    Quote Originally Posted by ArmyofDarkness View Post
    Google is where I found them, I doubt your LHS would carry them really, more of an electronics store kinda thing ( radio shack & such ).

    If we had known there was a smartstop involved, that would have been the first thing I'd have said to look at or remove to trouble shoot the issue...
    If I would have known about the smart stop I could have given it to you. At least we have been able to get to the bottom of the issue. I did run the truck this evening and it ran until it got weak. YEAH!!!

  18. #18
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    Quote Originally Posted by ArmyofDarkness View Post
    Google is where I found them, I doubt your LHS would carry them really, more of an electronics store kinda thing ( radio shack & such ).

    If we had known there was a smartstop involved, that would have been the first thing I'd have said to look at or remove to trouble shoot the issue...
    Should be able to get them through Horizon Hobby under either the JR or Hanger 9 name brands, maybe even as a Spektrum part too. Don't know off the top of my head if Great Planes/Tower Hobbies carries anything like that though.
    Aw, Biscuits!

  19. #19
    RC Racer
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    Thanks again everyone for all of the helpful info. I guess the moral of this whole story is to find out exactly what your truck has on it when purchasing new or used. In my case this was a used truck the my LHS took in on trade and I actually traded my 9 year old 2.5 T-Maxx in on this truck. They knew exactly what had been done to this truck and most likely told me, but with being out of the electric arena for quite awhile I wasn't on top of what they were telling me. So, I had no idea what they were telling me originally when they told me that it has a smartstop installed. I know now!!

    This one great reason why these forums are important!!! I can't drive 45 minutes to my LHS every time I have an issue like this.

    Thanks again!!! I will work on getting a photo host site and post some pics, so you can give me any ideas of anything else that I should do to the truck. At this time I am not planning on running Lipo.

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