Recurring issues with USB and Mains connected.

I bought and assembled a Kossel mini kit that was pre-flashed with the firmware. It was able to communicate with pronterface via the USB however, when I plugged in the mains in order to control the steppers for calibration Pronterface stopped responding. Then the LCD went black and I couldn't get power back. The USB wire was hot to the touch. I then disassembled and flashed the firmware in case something was wrong with it and I managed to get the printer working again without any stepper drivers. it turns out my E0 stepper driver connectors were frying every stepper driver I put in to it and shutting the lcd off. The seller suggested that it would be the arduino that is the problem with a faulty 5 volt regulator and after they wanted me to check this by repeating mains and USB together it fried the arduino so they offered me a replacement at discount dismissing my concerns that the ramps board was killing every stepper that went on E0. I have re-wired the printer without the stepper drivers or stepper motors connected and flashed the firmware onto the arduino.

The same thing happened, worked mains only, connected to pronterface fine on USB only, but when both are powered it fails to connect I Quickly checked the USB wire and it was hot so I immediately disconnected it. Is the seller right in saying the ramps is fine? They checked all my wiring and I am certain it is correct.

Any help will be appreciated. Thanks.

... it seems, the GND's of your PC and printer PS were off some ten to hundred Volts and the difference causes a high current through the USB cable shielding and kills the communication ... this can kill your PC too!!

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

So how would I fix this? I have a dual wall socket, my PC is powered on the right passing through a surge protector and my printer goes through the left passing through a tp-link socket. Could this configuration be the issue or is there some wiring that is off somewhere? Glad it didn't fry my PC.

Found a way to check and I have 0V DC difference but a 25v AC difference by unplugging the usb from the ramps, plunging it in the pc and measuring from the shielding on the ramps and the shielding on the usb cable.

... the "decoupling" of one of the PS'es is different - either search another PS or conenct the two GND's with a thick wire before switching on ... and pay the electric bill

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Ok thanks I have had a look into this 'decoupling' business and I have no idea what to look for in a PS because the one i'm using is generic. Is there a safe amount of potential difference or is it 0 or bust? been trying different usb ports and my laptop has a much lower difference of 7v ac and 5v dc so proof of concept that I may be able to achieve a safe voltage on a different pc so going to try my friends imac later.

... this is a known problem when connecting the voltages of different sources, that are not "tight" to the same mains ground level.

Especially with notebook power sources the potential difference can be up to half of the mains voltage!

You can only try different power sources and measure if they have the same GND levels or if they are "off" ...

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Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]