Geeetech

Hi,

I had an issue yesterday. I was just about to level the bed, and there was a little "pop" noise, a small flash and smell of burning. Upon inspection is appears U2 on my GT2560 board is fried, particularly pin2 (VIn). The fuses didn't blow and it was continuing to get hot and smoke so was glad I was next to it at the time.

I got a new GT2560 today, only this time its an A+ rather than the A I had before. I conencted it all up and found the same chip was getting hot. Luckily I noticed this and removed power before any damage was done. After checking the connections I found the hot end thermistor was the cause of this and once disconnected the IC remains cool to the touch. The thermistor was reading open circuit and one of the legs was broken. I am guessing the pop and flash was possibly a short between then thermistor and hot end.

I have also found that all 4 of my A4988 stepper drivers are no longer working so guess these were also fried.

Does anyone know what may have caused this so that I can prevent it happening again? As I am now questioning the safety of this, as if the thermistor was shorted or open circuit then Marlin would have handled this, however not sure what would of happened if the thermistor had shorted to the heated block.

Sad situation.

Although you have tried to describe quite accurately what happened, it can be difficult to diagnose the cause of a fault at a distance.

I would first check if the voltage from the main power supply is correct.
Next, I suggest to disconnect all peripherals from the controller board and connect the power supply. A laboratory power supply with the measurement of current and voltage at the output would be very convenient.
Of course, it is important to watch closely what is going on.

If the chip of the inverter is damaged in such a brutal way, it may be a short-circuit. It can also be an incorrect voltage connected to its outputs.

The rest is a continuation of this event.

Looks like I found my issue. My heater cartridge appears to be shorted to its outer casing, so although it works, it also causes the whole hot end to go +12v.

Guessing the thermister then shorted to the block, hence the pop and spark, and then blew U2, and all the steppers and possibly other stuff on the board.

Annoying! New heater cartridge and steppers on the way!