I had an EasyDriver 4.2 - hooked it up recently and poof.
I had only 12v power + gnd from PC power supply hooked up.
I had the motor hooked up correctly (I this thing breadboarded, and the motor has a .1" spaced connector at the end to plug in to the breadboard)
the 12v tests out at 12.2v (should be ok)
the motor tests at 34ohm for each pair, and no shorts between them (inf resistance between non-connected pairs)
any ideas What I might have done? - I DIDNT have any other pins connected - STEP and DIR and GND were hooked up to a non-powered Arduino Mega.
I did not have the enable pin connected, or anything else really… arg… I have 3 more but don’t want to smoke any more of them… so I’d like to know what I did before I go doing it again.
On quick check - the STEP and DIR were hooked up to the +5v pins, but un-powered arduino. GND was hooked to the arduino GND…
FWIW I risked it and popped in another easyDriver, and the power LED came on - no problems. Which I noted the power LED didn’t come on on the failed EasyDriver - but still SMOKE- no power LED, smoke… no power, just smoke poof.
I also checked the power supply 12.2v
I also checked for shorts on the stepper motor cable - A1 A2 34ohm, B1 B2 34ohm, all other combinations inf resistance.
So, looking at that last picture, I clearly see that smoke came from near pins 5 and 20. Those are the two pins that bring power into the chip (12V in your case). I’ve never seen a driver chip with burn marks like that before, but my guess is that some stress caused an internal short between pins 5 (and 20) and GND, and the weak link in the chain was the connections right inside the chip at those power input pins. I have no idea why that would happen, but maybe a power surge or something? Maybe your computer power supply surged when first turned on or something, and put more than 30V into the ED. I’m very sorry to hear about your loss, but from what you’ve told me it doesn’t sound like you’ve done anything that should have caused this to happen.
I re-did the entire circuit - and aside from choosing diff digital output pins - everything is the same as it was (unless I made some mistake somewhere in MY wiring) - the difference being NOTHING SMOKED AND EVERYTHING WORKED.
yes a power surge from the power supply is possible… so I guess the question I have is - hey, can I just pick up another chip and replace it? I mean - from what you said it LOOKS like it was something freakishly wierd and internal (good for the board if it’s just the chip)…
besides I’ve been meaning to put forth some effort to get good at soldering chips like this. so hey, fried chip = opportunity to learn/fix/learn
thanks again for the quick response.
FWIW the easyDriver has been in storage, packed in the pink esd foam, packed in a box. was in check luggage 3 times, and well… who knows.
Anyway… good news is that the other board works without any problems.
poof.
so hey, fried chip = opportunity to learn/fix/learn 
