APM 10pin IC blown for literally no reason

I’m very sorry if this is the wrong forum for this question, but I had absolutely no idea where to put this topic, so if it is the wrong place, please change to the correct category :smiley:

Hi everybody!

I just connected my 1 month old ReadyToFlyer 2.8 (set up as a 2.6) to my computer via USB and it was all working normally. I have not flown it for about 2 weeks, and wanted to prepare for a flying tomorrow. I disconnected the USB cable and connected my LiPo, and when connecting there was a big spark at the connection, and smoke was coming out of the APM! I have done absolutely nothing with this board since I flew it 2 weeks ago, and it was all working over USB, but now it blew up. The 10S power module from HobbyKing is delivering a pure 5.14v.

Here is a picture showing the defective APM

As you may see, the 10pin IC on the right side of the 2560 has blown, but I don’t get why! Actually, when I connected an older APM I have laying around a few minutes after this incident, that board worked flawlessly! HERE and HERE are pictures showing the other APM, connected EXACTLY as the now defective ReadyToFlyer, and it works without any problems at all!

I appreciate every single answer! Thank you very much! :slight_smile:

Is your APM a genuine 3DR product or a clone?

Have you not wondered why RTFQuads can sell these for only $39? Even Hobbyking’s price is more than that. Nothing especially wrong about using clone boards if that’s what your budget will allow, but you shouldn’t be too surprised if something just blows up for no good reason. Not that it couldn’t happen on a 3DR board, but I think it’s less likely. You saves your money and takes your chances…

Sorry to hear that. Let’s take a closer look what might have happened.

The toasted chip appears to be Texas Instruments’ ts5a23157 Dual 10-Ohm SPDT Analog Switch.
It is used in the APM as the multiplexer which switches the Mega2560’s UART0 serial between telemetry and USB, some info here.
As this chip is simple low-current signal routing, it’s having smoked would seem likely to be caused by a fault inside the chip itself.

See if you can get a replacement APM from Witespy. If it’s too much trouble, too long ago or too long a wait, simply sticking in a replacement chip may well fix it.

Good luck,