Old Sanwa receiver

I came in a slightly complicated situation when I had to fix an old RC car
recently. The old setup consists of old Sanwa servos and receiver. One servo
(and now also the other) broke and I replaced it with a new Futaba. To get
this to work in the system I had to switch the positive and negative cables.
I realized this after some trial and error, and I guess I might have
affected something in the receiver during this.
Now the receiver mirrors the directions of the servo's turnings. When I pull
the steering stick to the left the wheels turn right, and when I press the
power stick forward the car backs and vice versa! Do you know how to change
the directions or "polarity" of the receiver?
Another quesition; do you know if a new receiver will work with my old
remote control and the crystal?
Reply to
Espen Johannessen
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Car? Anyway...
First, re-evaulate mechanically reversing the action (i.e take off the servo arm and put it back on 180 degrees out). To reverse the action electronically, there are a number of things that can be done. But if the idea is just to get it working again quickly and without expense and you are willing to mod the radio then I would add channel reversing switches to the transmitter (assuming it doesnt have them already), or just reverse the controls permanently if that is appropriate.
Each axis is probably controlled by a potentiometer, with a tap for the center and two more taps, one for each end. If you swap the end taps on each potentiometer individually you *should* effectively reverse each individual channel. If by some chance one of the leads isn't connected then move the end tap to the unused lead. Note, I haven't actually tried this on a transmitter, but I don't know why it shouldn't work, unless you have bizzare potentiometers or are a spaz with a soldering iron.
The pot is probably round with three leads coming out (I've labeled them A, B, and C)
--O A ---O B --O C
So you would unsolder A and C and resolder C's leads to the A potentiometer terminal and A's leads to the C potentiometer terminal.
There are probably circuits that you can buy or build, but one can do the above mod in mere minutes and costs nothing. Just make sure the potentiometer leads dont bind or rub more than they did when you work the trims. Failing all that you are probably due for a new tx and rx, they are dirt cheap for cars.
Reply to
Steve Banks
Just a follow up after some bench experience. I did find reason to experiment with some transmitter joysticks recently and there is one caveat: you *may* need to "recenter" the pots, that is if after you switch the ends on the pots, make sure you have an equal amount of servo travel in both directions with the trim tabs reasonably close to centered.
I couldn't stand the two stick radio on the accipiter, and I had an ancient Circus "shoot 'em all" 72 mhz radio with 2D sticks on it (and I couldn't bring myself to throw a way a perfectly good 27 mhz transmitter/receiver). So being the goofball I am, I decided to combine the two, using the sticks/box from the Circus and grafting everything else (including antenna) from the Accipiter onto the back. The resistance range of the pots was a good match, but the travel on the servos was not close to symmetrical, even with trim. I had to pry apart a couple small melty bits and recenter the pots and put a drop of CA to secure.
Anyway, the result is really fugly, but it goes so well with the crapippitier extreme ;) I'll post some pics if there is a prize for cheapest/ugliest equipment.
Reply to
Steve Banks
thanks for the help it worked fine on my Sanwa GC220
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