Might have a failed voltage regulator on the board.

My Espruino died today. When plugging in the USB or battery it did not seem to work. Trying to enter boot loader mode did not work and no flickering from the LED's. I measured voltage levels on batt and 3.3 with USB plugged in. Bat was 4.9 volts 3.3pin reads 0.7 volts. If I connected a 3.3 volt power source to the 3.3v pin next to bat the espruino works and I am able to send commands from the serial console via USB. Is there a fuse on the board or which component number is the voltage regulator?

My Espruino died today. When plugging in the USB or battery it did not seem to work. Trying to enter boot loader mode did not work and no flickering from the LED's. I measured voltage levels on batt and 3.3 with USB plugged in. Bat was 4.9 volts 3.3pin reads 0.7 volts. If I connected a 3.3 volt power source to the 3.3v pin next to bat the espruino works and I am able to send commands from the serial console via USB. Is there a fuse on the board or which component number is the voltage regulator?

There's a self-resetting 1A fuse on the board... But that shouldn't be the issue, since it's supposed to be, well, self-resetting...

U4 is the voltage regulator, according to the schematic ( https://github.com/espruino/EspruinoBoar­d/raw/master/pdf/espruino_schematic.pdf ) it's a MIC5205.

Thanks @DrAzzy - yes, that's the one - a little dual in line 5 pin package.

Strange that it's blown though - did anything happen that might have caused it problems? Also, when you power up the board via 3.3v, how much current does it draw? It could be that the vreg is working but something is drawing too much current... 0.7v almost sounds like an IC is connected backwards somewhere?

Its was working fine. Not aware of anything bad happening to it. It draws 8ma when switched on. I removed the bluetooth in case that was the source of the problem. It works fine if I connect 3.3v to the 3.3v pin hence the reason I figured it was the voltage regulator.

Thank you. @DrAzzy

8ma sounds fine. Unlikely to be any problems there then.

Yes, that's really strange though - first one I've ever heard off with any voltage regulator issues. What country are you in? If you want to send it back I can fix it for you, or I could send you a new voltage regulator chip if you're happy with SMD?

By the way, it's a 3.3v MIC5205, so the part number is MIC5205-3.3

I have a LP2985 3.3 volt regulator on hand. Looking at the pin outs I think it will be a drop in replacement. So I can try that if you don't see any reasons it would not work.

Replacing that voltage regulator fixed the problem. The board was only powered with USB and LiPo but occasionally a component fail before its mean time to failure. Gordon thanks for your offer to fix or send me components.

Glad that sorted it! Thanks for fixing it yourself :)

I'll keep an eye open for any other failures. I'm actually swapping the regulator in the next revision anyway. Sadly it's not pin compatible, but I'm using one with a lower quiescent current as in deep sleep the MIC5205 (and seemingly your TI part too) take about 80% of the power!