[bo.gardmark]

Hi! I have a CNC3020 Chinese router. Unfortunately the motor speed controller has been broken. The spindle motor is dead. Checking the controller card, see attached photo, I can see that one resistor has been badly smoked. It is R1. R1 is connected to the ground pin of U2, a 78L05 5 volt regulator. Checking the output voltage of U2 it is found to be zero. I will replace the U2 IC as well as R1.

My problem is that I can’t see the value of R1, it is too heavily toasted. Could anybody that has a CNC3020 help me to check the value of the resistor? It has to be replaced.

Thanks in advance!

Regards

Bo, SM6FIE

[blinkenlight]

I have a YooCNC 3020, but my spindle controller looks *nothing* like the one in the picture, it even has entirely different terminals. Sorry, no idea what your circuit or R1 value might be...

[bo.gardmark]

Thanks for the help. I finally managed to find a solution to my problem. I will address that in an upcoming post.

Regards

Bo, SM6FIE

[bo.gardmark]

I managed to repair the spindle speed controller. It was difficult to reengineer the PCB due to the fact that the vendor had deliberately removed the labeling of some components (IC, Transistors).

The fault was two drive transistors that were shorted and a 5 volts regulator that was broken. After replacing the components the device works again.

I did some notes during my repair efforts and attached them. If somebody else get the same problem the document can give some help and guidance.

Regards

Bo, SM6FIE

[Al_The_Man]

If all the destination pinouts of U1 are shown it might be possible to reverse engineer it?
I would suspect that U3 - U4 are Mosfet's?
Al.