By mistake, I applied 12V to the “Raw” input of my serial LCD (see link below), outside the 3.3-9V range. The display went black after a few seconds. My hope is that maybe it’s just the voltage regulator that got fried, not the rest of the display. Is the tiny chip labeled J3 (it reads “KB33” on the chip) the voltage regulator? If so, I’ll try to replace it. If replacing the regulator won’t be enough, are there any other relevant electrical components (resistors, caps etc) I should also try to replace?
Hello element!
Sorry that happened! I’ve done the same thing before on other boards.
What you might try first is applying 3.3 volts to the “+” pin just to verify the rest of the LCD is still functional before replacing the voltage regulator. I mention this because sometimes when these regulators fail, they allow the full input voltage through and that would have fried the rest of the chips on the display making it essentially un-fixable. It would suck to replace the Vreg only to find out there’s other parts that are dead too.
If that does work and the display functions correctly, what you need is a MIC5205-3.3BM5-TR voltage regulator and you can find those at Future Electronics. The link below should get you to one. 
That datasheet for that part shows up to 16V of input voltage is ok. Is that the same part that was originally installed? It’s not likely that 12V would fry one of those.
That's for the info. For power, I was using a 1A / 12 V wall wart, which was also powering an Arduino Mega, and a few servos (separately, through a step-down to 5V). When measured with a multimeter the wall wart output is actually 14V. Not sure why, perhaps cheap wall warts supply more voltage than specified. The display is still black. Once I get the replacement regulator, I'll deal with it, including a test if 3.3V delivered directly to the "+" still works.darrellg:
That datasheet for that part shows up to 16V of input voltage is ok