Connecting usb to laptop and laptom shuts down when printer is powered up

S550Stang 2018-03-13 00:40:16 UTC #1

Finished the build and loaded the marlin firmware. downloaded and installed repetier and turned on the printer. laptop shut down. 9 volts measured from printer thru cable... triple checked my wiring. and tuned stepers. wtf!!

S550Stang 2018-03-14 11:22:13 UTC #2

Working with Folgertech support team. Hopefully resolved quickly.

S550Stang 2018-03-15 14:04:06 UTC #3

Still working through, but Folgertech support has been great. looked like a short with a couple of the board mounting screws. Got the bed moving in the X and Y, nothing moving on Z yet.

S550Stang 2018-03-19 15:07:41 UTC #4

x y are homing.. z, still nothing..
runaway heater on the bed.

S550Stang 2018-03-20 16:13:03 UTC #5

Swapped driver on Z, now working.. heater runaway issue is gone.. no clue what happened there... something is going on with the y stage, may just be belt/alignment.. but I'm pushing plastic!!!!

S550Stang 2018-03-28 11:04:36 UTC #6

Still working with Folgertech team.

Y stage is working, was a belt/ voltage/alignment issue I believe.

Was able to make a 20x20x20 cube, some drift.. The print head assy was coming away from the bearing carriage. Turns out the screws called out in the build guide are not long enough to engage the threads. Temporarily holding with zip ties...

Hot bed taking 20 min to get to temp, only 1/2 the board is getting hot. Need to measure the resistance and get the info back to Dustin.

I was able to print PLA at least with the cold bed. tuning continues.

S550Stang 2018-03-30 15:15:14 UTC #7

Not sure what the resistance is suppose to be, but I am measuring 3.6 Ohms. Waiting for Tech support to get back to me. Anyone care to chime in on what the resistance should be?

S550Stang 2018-04-03 11:27:17 UTC #8

Desoldered, here are my readings 1&2,1&3, and 2&3

carefudundae 2018-04-04 01:37:46 UTC #9

I'm not sure if this will help, but a long long time ago I had a weird power supply issue after mounting it to a plastic bracket. Long story short, the mounting screw was too long that threaded into the power supply and shorted the case to the positive terminal. Everything ran fine because it still put out 12V, but the positive side was referenced to ground (0V) and the negative side, instead of being 0, was -12V. I figured this out when hooking up to my computer and the usb cable instantly started getting hot. I luckily didn't fry anything (somehow), but got a good lesson in floating voltages and such. Maybe this won't help, but in my situation if it was connected to a laptop it likely would've shut it down (was connecting to a desktop instead). FWIW
I don't have an i3, but a few ohms sounds right for a 24V heated bed. They are typically a couple hundred watts of heat output, so 24*24/3.6=160W (7A). If you have a 12V power supply, then that resistance is likely too high (only 40W of heat).

S550Stang 2018-04-04 11:35:13 UTC #10

Thanks for the response. I believe the feedback was from mounting screws on the ramps board. The heads were too big and shorting. Once I removed the offending screw(s) all worked. I have sent Folgertech the pictures and the readings, hope to get a response soon as the printer at this point is down.