Today I finally managed to break the control board. 
I would like to share the findings I made before it broke:
-The cables of the motors were heated and the outer plastic parts had become soft due to the heat.
-The DRV88 series drivers were too hot to be touched by hand. They were so hot that the adhesives of the cooling aluminums had almost melted and the coolers were about to sag and fall. (It seems that even the cooling of the 12v high-speed fan did not work)
-When I first turned on the machine, there was no problem with the work I did in a square shape. Then, after trying to write a complex text, it moved properly in the first turn. Then it started to deviate. The movements started again intermittently. It also started to miss steps.
-In the end, it gave a warning that the USB connection to the laptop was lost. Also, the LCD screen remained white.
The question is: The motors I have are Sanyo brand, maybe a little bigger than Nema17. How do I know how to adjust the potentiometer on the driver for these? In other words, how do I know how many volts I should set it to? Eventually I’ll get a new control card so I don’t break it either. Of course I’ll have to change the cables too.