Rambo USB power surge

Recently configured a Rambo, programmed with Marlin 1.0.0 RC2. Worked fine, motors, temp, monitor, etc.
Turned the Hotend on, and watched as it climbed to 177C.

Then noticed that my USB cable was hot (starting to melt), and the USB port on the Rambo was melted.
I did have the Power select jumper set to PSU.

Any ideas what could have caused this?
Does the jumper have to be set to USB if you don't have an SD and are programming from the pc?

Thanks for any help.

Yet another one who connects USBs 5V to the power supplies 5V? And the electronics designers are stupid enough to allow such a configuration.

---

Generation 7 Electronics	Teacup Firmware	RepRap DIY

A cheap PSU with GND at a higher voltage than mains GND caused the other similar case. Please check for a differential voltage between (-) on your PSU and your PC case.

Traumflug: There is no way to connect USB 5V to the PSU 5V on RAMBo. It is jumper select. VCC is sourced from either USB or the onboard SMPS.

Quote

There is no way to connect USB 5V to the PSU 5V on RAMBo.

Perfect!

---

Generation 7 Electronics	Teacup Firmware	RepRap DIY