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Old 11-11-2009, 02:47 PM   #1
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Default Two dead throttle servos. Coincidence or something else?

ive had an older hitec 645mg in my car for over 6 months, and its always worked great.

last thursday while practicing for the sidewinder race everything was working fine. saturday morning i show up ready to run. i get my car togther to run the morning practice. As im waiting in line to run i am warming up the car. while its warming up, the throttle servo died spontaneously for no reason.

so i skipped practice and i go borrow another racers older 645mg spare (thanks Tabinator!) and throw that in and get ready for the first qualifier. this time i make it onto the track and unfortunately i broke a rear hub during the warm up laps. so i skipped the first qualifier to go get the car ready for the second qualifier.

so come time for the second qualifier. im again waiting in line warming up the car, and for the second time that day the throttle servo dies while im warming up on the bench.

i am completely stumped as to weather this was coincidental or if something else is awry. all my end points were set properly, batteries were charged. i also checked the wires on both of the dead servos and there were no nicks, cuts, or any obivious damage. neither smelled of burnt electronics.

i know the 645's are low end servos but ive never had any problems with them in the past. and to have two of them die in the exact same fashion is weird. i have ordered a hitec 7985 servo as a replacement. hopefully something a little more high end will be more durable, but i am nervous that its going to die now for some mysterious reason

so i come to the citizens of RCTech to lend me your ideas as to my dilemma.
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Old 11-11-2009, 03:17 PM   #2
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Check your lug nuts, body clips and antenna tube. They are most likely loose and causing your problem. I had this same problem, and they were the culprits!..................................:l ol:

Did ya check the servos in the other port to make sure the servo was bad, and not something in the recv'r? Sounds like it may just b a coincidence. I was having servo issues a while back, and it was just that fact that they were all old and going out. Put new ones in, and good to go. Sorry about your horrible weekend! What a bummer! I HATE servo/electrical issues!!
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Old 11-11-2009, 03:27 PM   #3
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Not much of a dilemma. I have seen stranger things happen with less expensive servos. Could have just fried from the high voltage of the battery charge, motor may have just given out, circuit boards have technical issues..Its just a freaky cheepy. here's the good news. You can send it back to Hitech and they will replace it and now you will have a capable back up in case you have a problem in the future with your "good" servo.

Just to be safe, you may want to have your RX checked, its possible it has a freeky circuit board and may be doing some weird voltage thing to the throttle servo only
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Old 11-11-2009, 03:37 PM   #4
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Check your lug nuts, body clips and antenna tube. They are most likely loose and causing your problem. I had this same problem, and they were the culprits!..................................:l ol:

Did ya check the servos in the other port to make sure the servo was bad, and not something in the recv'r? Sounds like it may just b a coincidence. I was having servo issues a while back, and it was just that fact that they were all old and going out. Put new ones in, and good to go. Sorry about your horrible weekend! What a bummer! I HATE servo/electrical issues!!
with my bad string of luck lately, im getting used to it

yeah, i switched the ports on the receiver, and the throttle was still dead on the steering, and the steering worked fine on the throttle. Mark's gonna lend me one of his old backups so i can run this weekend at ARC. new one should be in next week, so we'll see
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Old 11-11-2009, 03:39 PM   #5
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Not much of a dilemma. I have seen stranger things happen with less expensive servos. Could have just fried from the high voltage of the battery charge, motor may have just given out, circuit boards have technical issues..Its just a freaky cheepy. here's the good news. You can send it back to Hitech and they will replace it and now you will have a capable back up in case you have a problem in the future with your "good" servo.

Just to be safe, you may want to have your RX checked, its possible it has a freeky circuit board and may be doing some weird voltage thing to the throttle servo only
i thought the same thing too about the battery, but i didnt even peak it before the second time it happened so i dont think it could have been any kind of overvoltage

im packing everything up to send to hitec. i want to see what they say about them. thats going to be the ultimate word of what happened
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Old 11-11-2009, 04:05 PM   #6
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I have seen stranger things happen. I even blew up a JR 9100HVS servo. JR said that I gave it too much current and melted the brushes in the motor. All I am running is a losi 2s lipo unregulated and these servos are supposed to be designed for that. Sometimes servos just go out. I have gone through at least 8 throttle servos this year. Some of them were due to hitting the side plastic mud guard, once I corrected this I only lost 1 more, the fancy over priced HVS. I am starting to think the high speed servos do not belong on throttle/ brake duties. IDK servos are strange things, I find that they either work forever or not at all. Hitec will tell you whats up with the servo they are very good at diagnosing issues.
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Old 11-11-2009, 04:22 PM   #7
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i run futaba high speed good torque cordless servo on my throttle and never had burn out on me but i do use a nimh reciever battery not a lipo,my guess is if u use lipo and run a high speed servo maybe it gets to much power and makes it to fast and burn up i run a radio tray also so that proberty helps
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Old 11-11-2009, 04:48 PM   #8
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Originally Posted by fatdaddy View Post
ive had an older hitec 645mg in my car for over 6 months, and its always worked great.

last thursday while practicing for the sidewinder race everything was working fine. saturday morning i show up ready to run. i get my car togther to run the morning practice. As im waiting in line to run i am warming up the car. while its warming up, the throttle servo died spontaneously for no reason.

so i skipped practice and i go borrow another racers older 645mg spare (thanks Tabinator!) and throw that in and get ready for the first qualifier. this time i make it onto the track and unfortunately i broke a rear hub during the warm up laps. so i skipped the first qualifier to go get the car ready for the second qualifier.

so come time for the second qualifier. im again waiting in line warming up the car, and for the second time that day the throttle servo dies while im warming up on the bench.

i am completely stumped as to weather this was coincidental or if something else is awry. all my end points were set properly, batteries were charged. i also checked the wires on both of the dead servos and there were no nicks, cuts, or any obivious damage. neither smelled of burnt electronics.

i know the 645's are low end servos but ive never had any problems with them in the past. and to have two of them die in the exact same fashion is weird. i have ordered a hitec 7985 servo as a replacement. hopefully something a little more high end will be more durable, but i am nervous that its going to die now for some mysterious reason

so i come to the citizens of RCTech to lend me your ideas as to my dilemma.
if you can have somebody double check your linkage setup. iv spent hours making sure they are good. if you hear too much noise coming from a servo then there is binding.
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Old 11-11-2009, 04:55 PM   #9
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noise from the dingal servo when at netural cause my does that but when i go half to full throttle it stops buzzing is that fine i have cut a few coils off my throttle spring to let some tension off
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Old 11-11-2009, 05:07 PM   #10
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if you have had good luck setting servos up then im sure the noise you hear is ok. i just know from moving the carb into a more straight position there is always a better spot it seems to eliminate noise. its so irritating to spend so much time and still have too much noise. out of 20 gallons in 18moths iv only lost 1 270. my point is that from end points to positioning of carb to the height of the servo and then if its bumping somthing...there is a checklist to go through to minamize servo noise. it can be a real pain although after reading watching and hearing so many people toast servos and seeing how they were set up it explains alot. im running all ko right now whether or not that matters i dont know but they make absolutely no noise whatsoever. my old 9100 servo really never did either
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Old 11-11-2009, 05:13 PM   #11
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yea i had to move my carb to the left so the carb boot wouldnt rub on my diff cover and cause a bind even though i also tryed to sand down the cover on my eight so i cant have my stright
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Old 11-11-2009, 06:35 PM   #12
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if you can have somebody double check your linkage setup. iv spent hours making sure they are good. if you hear too much noise coming from a servo then there is binding.
yeah, its always good to have a second set of eyes on it.
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Old 11-14-2009, 07:42 AM   #13
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so you had an old servo go bad and the replacement old servo went bad too.... i hated the lowtech servos from day 1, always fail when the clock is running, on an open track day they will run fine all day, but as soon as it hears the transponder beeps they choke and die. i would check epa on throttle and brake, make sure the carb slider is smooth and the servo arm is not rubbing on the top of the servo case, (if so sand down the bottom of the spline part), also check the brake linkage is smooth. throttle and brakes must be in a straight line to the servo, the linkage is straight so the loine must be straight, unless you use a ball end on both sides of the linkage.
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Old 11-14-2009, 08:36 AM   #14
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the 90 diginal servo never failed me and i had my fail safe go to full brake a couple of times and others things now i do have the failsafe set to half brake now thank god and i been running these servos for about a year and a half as long as you have nothing binding or other things they will last maybe not in a truggy but in a buggy i cant see why they wount last
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Old 11-14-2009, 11:43 AM   #15
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the 90 diginal servo never failed me and i had my fail safe go to full brake a couple of times and others things now i do have the failsafe set to half brake now thank god and i been running these servos for about a year and a half as long as you have nothing binding or other things they will last maybe not in a truggy but in a buggy i cant see why they wount last


there's a difference in Driver ability when it come's to the Sportsman C main....as Apposed to the Expert A Main....most of the time when I see RTR gear surviving the day its normally in the hands of a youngster who in all honesty is going 1/4 the speed as the A main Tq pace guys....sure they crash....but not at Mach 1 trying to pull a TQ pace........so you look at it like that....well sure the RTR gear will last...but the second you ask a servo to go 45-60min of Hard blue groove abuse they will fail...the gear's are normally weak brass/plastic that wont take more then 1 good hit to cause a tooth to fail and the servo start to not center properly or outright fail from the motor's getting hot and burning up the brush's.....High end servo's have heat sinks for a reason.
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