From: cerulean@access.digex.com (Bill Christens-Barry)
Subject: new R/C car guy has problem, needs HELP!
Summary: speed controller reverse problem
Keywords: Kyosho, Optima, Mid
Organization: Express Access Online Communications, Greenbelt, Maryland USA
Date: Tue, 10 Nov 1992 02:29:03 GMT

I need help, please!  I have some questions about an R/C car (a Kyosho
Optima Mid 4wd that has a different motor put in by the previous owner) 
that I bought used the other day.  It has a Futaba FP-R102GR 2 channel AM 
receiver (29.965 Mhz) with a battery eliminator circuit.  It has a speed 
controller (a Nova 18-III) that allows for continuously variable forward and 
reverse speeds.  It runs on a 7 x 1.2 v NiCad pack.  Being new at this, I don't 
fully appreciate the significance of these things but figure it's probably 
useful for you to know what the context of my problem.
   Anyway, while my son and I were testing the car it developed a problem.  
It no longer will go in reverse as it would before we ran it into a dirt 
embankment (with low impact).  I see that the joystick correctly causes 
green and red leds on the speed controller to light when the joystick is 
moved to forward and reverse positions, respectively.  However, I hear a 
clicking kind of sound coming from the speed controller when I try to go in 
reverse and get no movement.  My son said that putting the joystick into 
reverse while the car is moving forward seems to deccelerate the car but 
has no other effect.  The offset trimmers on the radio transmitter seem to 
behave correctly so I don't think I have any problem there.
   All of this sounds like a relay problem, maybe brought on by the crash we 
had.  Does this seem reasonable?  My hypothesis is that the braking effect 
when reverse is joysticked is due to some minor amount of current going to 
the motor.  How reasonable is this?  What should I look for from the speed 
What should I look for if I meter things out?  Should I test it open circuit
by unhooking the motor and checking the voltage.  And am I reasonably
likely to be able to fix the speed controller if the problem is due to a bad or 
damaged relay?  It doesn't look like the unit was meant to be opened or 
serviced although I think I can do so nondestructively.  Can I get a 
replacement relay or will I have to buy a whole new controller?
   Let me add that the speed controller has two trimpots with markings that
allow some adjustments.  One is marked "neutral" and the other is marked
"proportional" underneath and has "hi" and "low" markings indicating the
effect of turning it in either direction.  I don't think these settings were 
disturbed by our crash.  Can someone explain what these are all about?
   Since I bought this setup used and on a shoestring budget I can't afford not 
to try to fix it.  Any help you can give me will really help me get this car 
back on the road.  Several more things - if I do need to buy parts, where 
should I buy them?  Is there a mail/phone order place that carries parts that 
I can use?  How do I know what is compatible with my car?  Any suggestions 
on a particular brand or model to use as a replacement?  Finally, I've been 
told that it doesn't do much good to the brushes in your motor to use
reverse.  Why is that?

Thanks for any comments or other useful info....

Bill Christens-Barry
cerulean@digex.com