To heat up a cable, one needs considerable current, so can assume there is an obvious short somewhere. Only need to identify where the short is located.
This should be fairly easy with a multimeter, just measure the resistances between the V+ and GND at each possible stage where the things can be disconnected physically. If you have a multimeter you can measure (powered off):
- resistance between 12V and gnd @your sanguinololu psu inputs;
- resistance between 12V and gnd @psu cable outputs that connects to above (+ check correct polarity);
- resistance between 5V and gnd @USB cable, with cable disconnected, to check if there is short inside cable;
- resistance between 5V and gnd @USB PC output, check for short inside pc usb power;
- resistance between 5V and gnd @USB board input, check for short on board;
Normally one of these measurements should pop out and point where the problem is.
Checked the sanguinololu schematic and i dont get much. I would use 5v from onboard regulator instead of using 5v from usb, and these 2 should be kept separated with a switch or smth, but from schematic these seem to be connected to each other, i would rather use a switch between. There is a switch, but that seems to change the endstops supply from 5v to 12v (i dont get why is that?) but you may check the status of that and if its on short or something.
As an experiment, you can try in reverse. With no usb connected, connect and power on the psu, and measure voltage right after the 7805 voltage regulator, to ensure that it does actually make 5v by itself. Its the big one on the far right side. The 3 legs should be 12v, gnd, and 5v.
This should be fairly easy with a multimeter, just measure the resistances between the V+ and GND at each possible stage where the things can be disconnected physically. If you have a multimeter you can measure (powered off):
- resistance between 12V and gnd @your sanguinololu psu inputs;
- resistance between 12V and gnd @psu cable outputs that connects to above (+ check correct polarity);
- resistance between 5V and gnd @USB cable, with cable disconnected, to check if there is short inside cable;
- resistance between 5V and gnd @USB PC output, check for short inside pc usb power;
- resistance between 5V and gnd @USB board input, check for short on board;
Normally one of these measurements should pop out and point where the problem is.
Checked the sanguinololu schematic and i dont get much. I would use 5v from onboard regulator instead of using 5v from usb, and these 2 should be kept separated with a switch or smth, but from schematic these seem to be connected to each other, i would rather use a switch between. There is a switch, but that seems to change the endstops supply from 5v to 12v (i dont get why is that?) but you may check the status of that and if its on short or something.
As an experiment, you can try in reverse. With no usb connected, connect and power on the psu, and measure voltage right after the 7805 voltage regulator, to ensure that it does actually make 5v by itself. Its the big one on the far right side. The 3 legs should be 12v, gnd, and 5v.
