Arduino clone woks only with USB - NOT with external power

Question

I have an Arduino UNO ch430 clone. It works with USB power supply, I can upload a Sketch and it works just fine. With external power supply, doesn't work. What do I mean? No LED lights up, high pins output ~ 0V. I'm using that barrel jack plug with 9V (6 x 1,5V batteries). Input voltage is measured OK. The AMS1117 regulator has Vin pin = Vout pin; i mean it gets no input Voltage. On the other hand, the M7F rectifier diode that comes between the jack and the regulator takes all voltage. I don't understan why, given that the anode is at higher voltage than the cathode (+9V). It shouldn't block current flow. I tried jumping the rectifier and getting the jack +pin directly to the Vin at the regulator: current starts to flow, but apparently so much that the ams1117 heats a lot and really fast. Well i don't know why it suddendly gets so much current, I have absolutely nothing pluged to the board and I couldn't find any stain or damaged spot on it.

I can't figure out what is happening. I hope you can help me, and thanks in advance.

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This is an exact (i'm pretty sure) schematic of my board. Link

Answer 1

It sounds like there's some form of short, or the AM1117 regulator is dead. Too much current being drawn by the regulator (as it gets so hot) has caused the diode to blow.

You will need to replace both the regulator and the diode and hope it works - or use a separate external regulator into the 5V pin instead.

Personally, I'd use a switch-mode regulator (UBEC regulators are cheap and easy to get hold of) since it is far more efficient than the LM1117.