pathfinder

Earlier today we had our power board fail in the same fashion as before. This time, the AND gate IC smoked dramatically. It seemed to take out the LDO, but the ADC seems okay (assuming it draws 50 mA in normal idle operation).

My new theory is this: the output cap on the LDO was 10 µF. According to the data sheet, any cap less than 1 µF can be used; if you want to go over 1 µF, it should be a cap with an ESR of at least 0.1 Ω. I don't know about the 10 µF cap I had on there, a Panasonic EMK212BJ106KG-T 16 V ceramic 0805 cap. I've replaced it with a 0.1 µF cap (I couldn't find a 1 µF cap), so hopefully that'll work.

I base my theory on this: Just after replacing the LDO, with lots of liquid flux still on the board, I powered it up. The new reg. was outputting over 5 V, and it kept climbing. I disconnected power around 6 V, for fear of damaging the ADC. After rinsing, the regulator performed well at 4.944 V, but I wonder if the 10 µF cap was causing it to go unstable, and to then output higher voltages, frying the AND IC.

Sigh…

P.S.—The other LDO is no longer regulating. It just puts out about what it gets. What the fuck is going on here? I'm going to try replacing the output cap on that one, see if it makes a difference. What a piece of shit LDO. I'm never using it again.

Replacing the cap didn't help. This means my theory is probably wrong, and it's something else that's FUCKING shit up.

I sure hope I didn't fuck up the ATmega128 running it at ten fucking volts for a few seconds. It seems to be running, but who knows what peripherals I've fried? Fuck.

Fuck. Fuck. Fuck. Fuck. Fuck. Fuck. Fuck. Fuck. Fuck. Fuck. Fuck. Fuck. The fucking MCU is fried now.

The ADC was bad, too.

I've replaced them all.

I'm exhausted. I'll do the open-loop 8 in the morning-ish. Here's hoping work doesn't need me…