A strange problem occured while 3D printing. I've been printing for a long time now, and I consider myself fairly expeienced. normally, with every problem I've encountered with my printers (Anet, Ender, Prusa), there's always an answer online. However, the strangest thing just happened and I cannot find an answer.
I upgraded my ender 3 to a 32 bit BigTreeTech SKR v1.3 motherboard with A4988 stepper drivers. I've printed several objects successfully. However, on one simple print, it suddenly stopped working. the LCD was pale blue and flickering slightly. even after turning the printer off, moving the Y axis by hand felt stiff and erractic.
Turning the printer on resulted in the same flickering pale blue screen. Doing a power cycle did nothing. at this point, I noticed my MCU and ONE stepper driver was scorching hot (~100 °C) only a few seconds after start-up. I unplugged the Y axis stepper driver from the motherboard and suddenly the printer could turn on again (bootup sequence executed). All the controls on my menu still work (even moving of axes, as tested with working drivers). However, the reading on my thermocouples are all way off now, reading 55 ° Cat 30 °C room temperature. Note that the MCU was still scorching hot even when doing nothing.
Some additional info to note, the stepper motors themselves were warm while printing, but not unbearably hot. The Vrefs (current sense resistor 0.1 Ω) were tuned to supply 0.75 A to the axes and 0.9 A to the extruder. I also attached small heatsinks to the drivers and have a small fan blowing on them. I'm running marlin-bugfix-2.0.x. also, on the 4th last layer before the print failed, there was a very slight layer shift on the X axis. I've also reflashed the same firmware onto the board, but it's still hot enough to fry an egg. the board also can't connect to Pronterface anymore.
I can always swap back with the stock Ender 3 motherboard, but I want to know what's the reason for this tragedy so i can prevent the same mistake.