Asahi Atcomi toy car 1980

[Reellgi]

Hi, anyone got this model, or similar like Porsche 930 or 924 from '80s? I need some photos of pcb or info about electronic boards. 

Many thanks

https://www.tamiyaclub.com/showroom_model.asp?cid=128046&id=15762

[korreka]

Those 80´s toy grade cars  have 6 functions control (7 functions including Stop).

Here is a Nikko car with those functions:  http://reparar-cochesrc.blogspot.com/2015/12/emisora-nikko-de-6-funciones-y.html

Nikko used a square signal (50% duty cycle) for "forward - 350Hz" and "backward - 900Hz".
On the "right" side it was 75% duty cycle and on the "left" it was 25% duty cycle.

Taiyo used the same signal and frequencies but forward and backward were swapped.

 

Other manufacturers used other I.C's decoders but the control signal was the same (the square signal frequencies could be different).
Some of these i.c.´s are:

TA7657
T8140

 

[Reellgi]

ok, thanks for explanation!

 

 

[Reellgi]

 finally  found a photo. But if the model is  full function type, why is there a potentiometer on the steering? Usually, at least in the small models, the neutral position is obtained with a spring and no signal in the steering motor. It looks like a servo.

[korreka]

It´s a semi-proportional control car. The steering is proportional control and a single speed to go forward or backward.

SN76604 i.c. was widely used the for steering control.

[Reellgi]

you were right! two sn76604 and one 14069, so is full proportional?

 What was  the hex inverter used for?

[korreka]

It may be a flip-flop or monostable multivibrator built with inverter gates to separate the PPM signal into two PWM signals:

[Reellgi]

there is a 1Mohm resistor near the 14069...maybe is one stage used as amplifier?