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Old 12-16-2008, 07:53 AM   #1
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Default ANALOG TO DIGITAL SERVO MIGRATION ISSUE

Hi,

I just swpped out my basic run of the mill analog steering servo for a Futaba 9550 digital servo on my TC5.

I have the futaba 3PM 2.4 radio and went through the long list of steering adjustement etc and I still find that witg the digital servo, the car is almost uncontrolable. It is just extremely sensitive to any input.

Again, I went in to steering timing , delay range abd cranked everything down a major amount and it is still rediculouslysensitive.

Is this just the way it is?? If so, then I actually like the controllability and predicability of an analog servo and i would probably go back to one.
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Old 12-16-2008, 08:44 AM   #2
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We ran JR590's for years and I finally replaced all three with JR8800's the digital servos.

I've never noticed what you are describing. It did give us faster more precise steering but nothing like you describe.

Can you go back to "factory defaults" on your radio?
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Old 12-16-2008, 08:49 AM   #3
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I would not want to go to factory defaultssine al of these are at 100%

I have steering response and delay etc at no more than 50% and it is still extremely sensitive...it is essentially always having very fast oversteer
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Old 12-16-2008, 09:00 AM   #4
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Does it have a toggle between HRS and PPM? Make sure you have it set to HRS.

And you should see big a difference in quickness\torque from your old run of the mill servo.

Last edited by Apex; 12-16-2008 at 09:11 AM.
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Old 12-16-2008, 09:01 AM   #5
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First off - welcome to the digital age.
Now to your questions - the 9550 is a fast servo when compared to a "run of the mill" analog servo, that would be the first thing you would notice(could be twice as fast or more).
Depending on the setup you have on your car the extra speed could upset the handling when the steering is applied.
If you find the steering to be "on a knife edge" around the "straight ahead" position just go to the expo feature of your tx and dial in 10 or 20 percent of negative (minus), that will "dull" the sharpness of the movement from center to either side, the rest of the setting of the tx are the same as any other car you have set up in a diff memory.
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Old 12-16-2008, 09:09 AM   #6
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My point about getting the radio back to default is that there may be some settings that are way off. Essentially give it a fresh start.

Out of the box even with a 70 dollar radio that servo shouldn't be out of control as you describe it.
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Old 12-16-2008, 09:49 AM   #7
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Quote:
Originally Posted by big_boss View Post
First off - welcome to the digital age.
Now to your questions - the 9550 is a fast servo when compared to a "run of the mill" analog servo, that would be the first thing you would notice(could be twice as fast or more).
Depending on the setup you have on your car the extra speed could upset the handling when the steering is applied.
If you find the steering to be "on a knife edge" around the "straight ahead" position just go to the expo feature of your tx and dial in 10 or 20 percent of negative (minus), that will "dull" the sharpness of the movement from center to either side, the rest of the setting of the tx are the same as any other car you have set up in a diff memory.

I did put it on the HRS mode, although i went back to PPm thinking this would slow it down...so it should always be inthe HRS?? yes knife edge is how I wuold describe and i had my Steering speed adjustment knocked down. Default is 100 and I set to 50..so I will go in and set a negative factor to so if that slows things down to my liking.

The one confusion I had was the difference between the Steering Speed (SPD-TN_ and the Steering EXP( EXT-ST)
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Old 12-16-2008, 11:05 AM   #8
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Quote:
Originally Posted by Fergup View Post
The one confusion I had was the difference between the Steering Speed (SPD-TN_ and the Steering EXP( EXT-ST)
Steering speed is the rate at which the servo moves throughout the entire travel.

Steering Exponential is the adjustment you make for the sensitivity at neutral or centered. Negative Expo ruduces the sensitivity as you start moving the wheel it retards the steering slightly as you begin to move the wheel off cente and give full steering the end of the wheel throw. Positive Expo will give greater steering with slight wheel movement from center.

The 9551 is not the fastest digital servo out there and as Kenji knows that it is the same speed as the analog JR Z590 so it's speed shouldn't be an issue.

Perhaps you are so used to a very slow weak servo that you were over compensating to control it and now that you have a decent mid-speed servo you find that it is more responsive and reacts to your tendancy to over control habit you picked up with the old servo.
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Old 12-16-2008, 11:16 AM   #9
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Are you running an esc that can supply the neccessary power to the Servo? I have had issues with digital servos when the power supply is less than stellar.

You could also try a capacitor in a spare channel on your RX. It may smooth out the power draw from the servo.

Cheers!
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