So what "power adapter plug" - what polarity, what voltage? - and is there a manual / datasheet for this module?
Is the polarity of the barrel jack socket marked / indicated (believe it or not these things are not standardised).
It does sound like a short circuit at the 5V side of things - do you have a multimeter?
There is no manual or datasheet for the product and no other info. Its from China; need I say more?
The adapter is an over the counter unit with an nominal output of 9 VDC at 800ma. The open circuit voltage is 13.5 V. I use the same adapter as the supply for the Arduino UNO board. The interior of the barrel is positive.
The 5v regulator is designated as ASM1117-5 whose datasheet I have attached.
I have followed the circuit on the schematic from the input adapter plug. The socket's center goes to the 1117-5 input pin 3; pin 1 is connected to ground and pin 2 is (at least) connected to the green LED. For a green LED voltage drop is typically 2.2v. So for a 5V supply the current through the resistor is (5-2.2)/470 = ~ 6 mA. So it must be something else.
I've traced through the rest of the connections and they all appear to be OK, but there is about 180 ohms between the 5V rail (1117-5 pin 2) to ground as measured with an ohmmeter. Reversing meter leads produces the same results. I can't think of what might cause that, but it would draw only 27 mA from the regulator whose max current is ~1 A.
There is no similar resistance between the 1117-3 regulator output and ground. Removing jumpers does not eliminate the 5V, 180 ohm shunt, nor does changing the DPDT switch.