Geeetech

Can anyone tell me which pair on the 4 pin plug for the dc inputs goes to the hot bed or hot end also on the later boards the 2 positive pins on the back of the board are bridged with solder any reason for this

I would say it's the part that looks brown and burnt just next to the 2 pin connector

with this set up which pair of dc wires supplies heatbed on the input from the psu on to the 4 pin plug I am setting it up now I suppose I could just disconnect one power line and see which one doesn't heat up

mine usually rectifies it self power on and off

The Mk2 heat bed look here http://reprap.org/wiki/PCB_Heatbed#About information on 12v and 24v
and general power usage http://forums.reprap.org/read.php?292,294743

Have a look at these they seem to be having the same problem (http://forums.reprap.org/read.php?158,130702)
Hope it's not to technical for you but it will give you some insight or something to work on

I don't think to low is it. have you checked heat plate for any shorts that could have shorted out as it's printing causing it to draw more than it should. I think that if the power supply was too low it would be causing it to trip out and it would be overheating.What temps are you heating your bed to

Can you monitor the power supply while you are printing there are some issues with the board and heat bed failing. Have a look at this and it shows that the board that you have appears tobe an older version (http://www.geeetech.com/wiki/index.php/File:27.Wiring1.jpg) Or this (http://www.geeetech.com...

Have you checked the output voltages of your power supply to ensure you not overloading your board it is supposed to be 12v

What do you mean pololus ? Do you mean mean trial error on the stepper adjust mean or can it be done using a multimeter is this to allow for the wire lengths to each one