First, thank you for your help. I have tried to regulate with the potentiometers on the card and does not regulate anything logical, transistor (darlington pair are ok), ok motors by regulating potentiometers logic board, the engines stopped working, I think that is the logic board, you think?

You can adjust the current limits for left and right traction motors on the corresponding pots on the logic card, so I'd start here with adjusting these. If that makes no difference then maybe need to look at current sensors.
Does speed change when you jack up the wheels and turn on full lock?
Confirm there is no short on either of the drive motors or to the chassis from them or the battery.