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Hitec 5745 problem

Old 06-04-2005, 11:20 PM
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madgti
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Default Hitec 5745 problem

I Just got an ew Hitec 5745 for my FG monster Truck. I plugged the servo right Out of the box on the table and i can immediatly tell the difference between the servo speed from turning one side from the other, and i also noticed it turns more to one side then the other.

MY controller has everything set at full and everything is dead center. Once the servo is mounted i have to set the end points on my controller to get equal steering. Right now i have my end point on my controller set to 18% on one side and 50% on the other side.

I tried to bring the servo back for an exchange and i was told they can not do anything about that.

Any ideas what could be wrong?

I am also running this servo with my JR XS3 controller.

Thanks
Old 06-05-2005, 12:19 AM
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mglavin
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Default RE: Hitec 5745 problem

There are a few things that can cause this problem. Before we go there have you driven the Truck?

FWIW: The 5475 or any Karbonite servo is poor choice for the demanding environment of a MONSTER truck. A metal geared servo is the best choice. Karbonites are NOT replacements for metal gears.

I'd be willing to bet the gear-train is damaged. If its not you may have a problem with the TX and its output pulses. Its very common for the output pulse transmitted at center and end-points to be off as much as 15-25us in either direction and center.. Sounds like your problem is more extreme than this, thus my assumption the gear-train is damaged.
Old 06-05-2005, 01:03 AM
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madgti
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Default RE: Hitec 5745 problem

I haven't driven the truck yet as i have not finished assembling it and i won't until i can get full steering. You mention i have a 5475 which is incorrect. I have an HS-5745MG. I think the servo is more then enough for the FG Monster Truck but correct me if i am wrong.

Looking at the servo on the table again without driving it yet i can not center the servo arm. Right now as it sits it seems to get equal range from stop on both direction. However i need to set the servo arm straight in order to get full alignmnet with my steering in both directions especially with the design of the FG monster trucks. If this was a little tie rod adjustments then i can live with it but by me not having the servo arm dead straight while using the JR XS3 to trim and compensate the offset of this servo arm then it really screws up my steering range on both side. SO after i center the servo arm with the controller i now have limited movement going one way compared to the other direction if the end points are set identical. Currently i am trying to get the same movement on both directions by compensating the end points like 20% on one side and 53% on the other side which isn't right. My brothers FG monster truck with the same controller and servos is not doing the same thing and infact is trim is set to 2 and his end points are set to 50% and have idental range in movement in both directions.

I need to know if this is a deffective servo or if it is somthing that can be calibrated from a hobby store so that i can have equal range in movment in both directions?

Thanks.

Peter
Old 06-05-2005, 01:27 AM
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mglavin
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Default RE: Hitec 5745 problem

The 5475HB is a Karbonite servo, no metal gear to the best of my knowledge.

Please explain in detail how you’re setting up the servo and TX.

The problem off center or deviations from center is atypical and varies with every TX.

I'll try and explain the conundrum:

Ideally your TX will transmit a pulse width of 900-1500-2100 micros seconds at end-point/neutral/end-point. But it’s not an ideal world and manufacturing and component tolerances skew the results.

Since your servo may not center exactly at 1500us and the TX outputs a different number too, things are amiss. This is where Hitec programmable digitals leave all others behind. With a Hitec programmer you can reset the servo to recognize the TX’s output as center and maintain linear travel either side of center.

As an example lets say your TX is outputting 1530us at neutral and maybe the servo is slightly of too, which is very common. Once you utilize sub-trim or trim to center the servo you’ve introduced a deviation and or offset in to the travel arc that now follows at end-points.

As you note the travel percentages are unequal, which is a result of using trim to center the servo. The neutral offset has to be absorbed; if the offset is 30 degrees in one direction the end-points should reflect same.

Another variable maybe your mechanical linkage set-up, if something is unequal here you’ll note this problem too.
Old 06-05-2005, 04:24 AM
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XJet
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Default RE: Hitec 5745 problem

I know I'm not supposed to post here and that you'll spank my ass for doing so but Mike READ WHAT THE GUY IS SAYING!!!!

He's got an HS5745 look HERE! servo, *NOT* an HS5475.

It *can't* be a geartrain problem because, to quote from the Hitec RCD website, these servos have "an unbreakable MP gear gear train" -- and we all know there have never been any outrageous claims in respect to the gearsets of Hitec servos made on the Hitec website (cough cough Kabronite cough cough :-)
Old 06-05-2005, 07:58 AM
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mglavin
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Default RE: Hitec 5745 problem

Whoops! Its 5745 not 5475......

I did the same thing last week........[&:]

Never mind the gear-train thing.

Do you know anyone with a Hitec programmer? With a programmer you could completely eliminate the problem, providing the servo is not suspect.

The programmer will allow you to record the TX output pulse as decoded by the receiver to determine what the micro-second pulse coded is at end-points and neutral. Plus you can reprogram the servo to recognize the TX trim’s zeroed output pulse at neutral.
Old 06-05-2005, 01:48 PM
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madgti
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Default RE: Hitec 5745 problem

Hey no problem.

No i don't know anyone with a programmer.

MY STC is set to 0
my EPA is set to 90 on both directions

With this setting i get full range in movement in both directions. BUt once i install it in the truck ofcourse i need to trim the servo since the servo arm is not sitting dead center and when it is trimmed i loose range on one of the directions.

Don't these servos come from the factory calibrated to be dead on?
Old 06-05-2005, 05:47 PM
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madgti
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Default RE: Hitec 5745 problem

i am using the subtrim right now from my controller to get the servo near where i want it.

Thanks
Old 06-05-2005, 11:20 PM
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mglavin
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Default RE: Hitec 5745 problem




With this setting i get full range in movement in both directions. BUt once i install it in the truck ofcourse i need to trim the servo since the servo arm is not sitting dead center and when it is trimmed i loose range on one of the directions.
As I mentioned the problem is the TX and its output pulse at neutral, you've verified same with your comments.

Don't these servos come from the factory calibrated to be dead on?

The servo maybe centered at 1500us but if the TX outputs 1530us at neutral the servo follows the command. As I noted earlier the programmer allows you work around the deviation at neutral realized of the TX. If the TX outputs 1500us at neutral the problem is the servo (there all typically a little off), this is common of every servo offered by any manufacturer. Only Hitec has the ability to reprogram neutral point to match the TX in use.
Old 06-06-2005, 09:31 AM
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madgti
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Default RE: Hitec 5745 problem

i mounted the servo on the truck yesterday and it responds very well.

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