1st build complete! mks mini v1.1board fried and HOT

Hello,

Thank you for being here 8)

I spent all day yesterday assembling an HK DIY131510A - looks beautiful!

Today I double checked all the connections, and applied power. The LCD screen came right on with some readings, and I could hear a faint whirring sound. All systems go, for five seconds. Then, it went dead. No sound, no lights, nothing except chip U3 gets too hot to touch in a few seconds, so I remove power. The power supply still has a green LED. I scanned the board for a fuse, but do not see one. Any thoughts?

Thanks again,

-James

U3 looks to be a voltage regulator... but the missing pin confuses me.. (probably using tab as third pin) (cant find any clear pictures that I can read the numbers from, so take everything as a educated guess)

Sadly this board is not open source so cant find anything useful on it.

Presuming it its a voltage regular, first thing to check is the voltage coming out of your power supply. If that’s 12v then check the output voltage of the regulator, one of them has to be an output, probably 5v.

Now if the voltage regulator is putting out more that it should, it's probably killed everything on the board. If its just stopped, you have hope that a new regulator will fix it.

Edited 1 time(s). Last edit at 02/29/2016 04:04AM by Dust.

Thank you for your quick reply! After removing the controller board completely from the unit, I powered it up and it came to life. However, once reinstalled, the same thing happened - on for a few seconds then dead/hot. I read through many other posts here and found a couple about the Z-axis limit switch potentially bringing a full shutdown due to a miswired condition, causing V+ to connect to ground. The last instruction in my kit before applying power the first time, is to manually run the head to Z minimum to make sure the switch gets hit before the print nozzle hits the bed. I had done this, causing my startup condition to be such that the Z switch was closed at startup. Manually threading the Z-axis motor off the limit switch got me powered up, but activating that one limit switch would instantly crash the board, and holding the switch down would heat U3 to burning temperature in seconds.

The X- and Y- limit switches did not crash the board, so I removed all 3, and their cables, and tested all with a continuity meter. The Z-axis showed a different result compared with the other two! The cable was fine, so I removed the connector, which was also fine. Removing the switch from the same little PCB revealed the switch was fine too!

The actual problem was a manual modification to the factory printed PCB that wasn't made to this board. As printed, the three pins of the switch are connected by circular trace, providing the option to leave any two of the pins to be normally connected. A close inspection revealed that someone had carefull cut the trace twice, but left the connection between pins 1 and 3, or V and S. Cutting that trace, leaving all three pins unconnected from each other on the PCB, it now matches continuity to the other two boards I have from the kit.

Finally, the momentary switch. When up, it connects pins 1 and 3, but leaves 1 disconnected from 2. When down, it connects pin 1 to pin 2, and disconnects pin 1 from pin 3. There is no condition when pin 2 and pin 3 are connected. Since my PCB had 1 connected to 3, pushing the switch actually connected all three pins together - lucky there was no fire!

Now I think it'll work - if saying so didn't just jinx it!!

Thanks again 8)