Quote Originally Posted by wingnut1000 View Post
Thanks for the clarification. I tested using AC volt mode and it does indeed show 0V. Thought I was doing it wrong.
How would I avoid powering over USB. Don't think I have control over it. I just ensure that I power on the power supply before connecting the printer to my PC
So from what we can tell, it's sounding like your power supply is OK. One additional clarifier would be to check the power supply output when you're heating up the bed and the hot end. That'll put a pretty good load on the power supply. For comparison, I ran a timed test on my i3v. It hit 110 degrees in about 8 minutes, although I have only 1/8-inch glass and do have the bed heater powered through a relay. Is the thermistor under the heat bed still snug to the bed? If that starts coming loose, it'll be slow to measure temperature changes. Your reddit post mentions 3/8-inch glass. I assume the 3/16-inch mentioned here is correct? 3/8-inch would be really thick stuff.

I've also looked at the board damage shown in the pictures. I have no answers on what is going on, but here's more information. Maybe it'll help someone else jump in with an answer for you.

For the ATMEGA2560 board, I used this as a representative schematic - http://arduino.cc/en/uploads/Main/ar...560_R3-sch.pdf. For the USB connector pinout, I used this as a typical USB type-B connector - http://www.mouser.com/ds/2/154/61729-335969.pdf. First, the schematic shows that the 22-ohm resistors in the two USB data lines are what your pictures show burning up. The part is marked as 220 since that's how the industry does it. The first two digits are the significant digits in the value, and the third digit states how many zeros get added. So, a marking of 220 means 22 ohms. These parts burning up is not good. Either there's a problem with one side of the interface driving the lines way wrong in voltage, or something has happened that has both sides of the interface trying to drive the lines at the same time.

The heftier trace in your third picture is almost more troublesome. If I follow the pinout right, that's on pin 4 of the USB connector, which is ground. What is the spot that looks like a spec on the first rectangle pad the trace goes to? Almost looks like something may have shorted there - especially since there's no discoloring after that pad. Ignoring that, I don't know - a bad cable shorting +5 to ground? Some really funky ground loop-problem between the USB shield and the ground pin, caused by some grounding issue going on between your computer and the printer?

Sorry I can't be of more help.