🚀 go-pugleaf

From article <9310016@hplsla.hp.com>, by davidc@hplsla.hp.com (David Cook):
>
> [stuff deleted about equipment description]
>
> was particularly apparent at slow speeds. Anyway I realized that since the
> Airtronics receiver is a BEC type I should not feed the regulated +6 volts
> from the controller back via the servo connector but should split it off and
> feed it to the receiver's battery connector. I did this and got some improve-
> ment but not what it should be. I can run the receiver with a seperate battery
> and everything works great. Why is the +6 volts from the MC12B not good 
> enough for the Airtronics receiver? I checked it with my meter and it is +6
> volts although I have not looked at it on a scope to see what kind of noise
> may be riding on it. Do I need another capacitor across the motor terminals?
> What is the proper configuration for motor capacitors?

I have raced RC Stadium trucks and 1/10,1/12 scale electrics for many years.  
If this jittering problem only starts when you apply some throttle control,
then it definately sounds like an incorrectly "capped" motor.  The Futaba
MC112B should have a MINIMUM of 3 capacitors on it.  The small .01uF or .1uF
disc-type caps (just the normal thin caps that come with most motors).
You should have one across the terminals of the motor (+ to -), and one from
each terminal to the case of the motor.  Be sure to "scruff" up the motor can
before you solder these connections, to insure a good connection.  If you were
using a high-frequency speed control, you would also want a fourth cap across
the terminals of the motor.  A polarized 4.7uF cap of at least 15V rating.
Be sure to observe proper + and - on these caps.  I would not suggest using
this fourth cap on the MC112B speed controller, or any other low-freq speed
controller.

Another possibility, if the jitter is present when all controls are at 
idle, is that your antenna is too close to the speed controller.  Try moving it
to another position on the car/truck.

Feel free to e-mail me if you continue to have problems.

-Jason Worley