Hot end commissioning

Not sure if there is another topic on this (Could not find one, or if this post is in the right place). But I am going through the commissioning process, everything has been good up to this point. But a few seconds after the hot end has heated up, and settled at the temeprature I set in pronterface, the printer loses contact with the PC and it says "Can't write to printer (disconnected?)."

I doubt it is because the hot end was hot for a certain amount of time, as you expect it to be all through a print. It has done this for all the temperatures I have set it to to test it, got up to temperature then loses connection. I have tried a few different cables, that I had laying around. I have formatted and reinstalled the files onto the SD card, even though I know that can't be the problem as it is reading the SD card fine.

I have messaged the support people, but thought to come to the forums as well. In case some one else is having this problem and knows a fix because at the moment, I am a tiny bit short on ideas. Any help would be appreciated.

Edited 2 time(s). Last edit at 11/07/2015 08:35PM by Craigy94.

You need identical setting for the Com port in Pronterface, Windows and your firmware.
But that is only a point for the general communication.
I strongly recommend to double or triple check yll connections, especially power, heat bed and stepper motors!
In 99% of cases where the communication fails catastrophically there is a problem with the power, loose or cooreded connection, connectors not fully pushed on, bad solder joints and so on...
One the power fails the printer tries to get the power through the USB cable from the PC - and the PC shuts the com port down as it uses too much power, the result is a total communication loss between printer and PC.

Thank you for the response, I will disconnect and check all the connections to make sure there is nothing wrong with them. I will also check the solder joints.

There are no problems while it is not heating up, it does not lose connection while I am rehoming the hot end. So I will start at the power supply and work my way through the PCB.

What PSU are you using? If using an old PSU from your PC, how many black wires are you using for ground? You need as many as possible and at least as many as your 12V yellow cables.
If you don't use enough of your PSU's black wires, what can happen is that the ground voltage be not stable and it can send current to your PC through the USB connection, thus interrupting communication.
If that's your problem,then all you need to do is minimise ground resistance ---> use more black cables from your PSU.

I have taken the back plate off and checked all the connections, they look connected. got the multimeter and checked that the power was coming through at the right voltage. I was getting just above 12v on the 12v line and just below 5v on the 5v line. so I heated up the hot end to see if these change while it is hot, but it has not lost communication, so the loss of connection must have had something to do with the back plate and maybe one of the wires. It is getting late and I have had a long day at work, so I will check if it still happens when I put the back plate back on tomorrow.