Accidently, I have damaged my Arduino Nano 3.0 board by shortcutting Vin and GND pins (because of bad soldering). Now the board can only be powered by USB. As I should use an external power supply, I tried to fix the problem.
According to the schematic, this board uses an UA78M05 (U3) as a voltage regulator. It was strongly probable that this part has been damaged. Unfortunately, I could not find the exact part nearby and I considered using an AMS1117 5.0V 1A Voltage Regulator (http://www.szhaolin.com/admin/PSystem/UploadPDF/200410161855527097.pdf). The only difference between these two parts is that the AMS1117 can tolerate up to 1A while UA78M05 can handle the currents up to 500mA.
I replaced the regulator UA78M05 with a new AMS1117 but it did not help. I measured the voltage on the regulator. The input voltage was 7.4V as expected (because of using a 2cell Lipo) but as output voltage, I measured only 0.3 V.
I tried another AMS1117 (while I have many) but the result did not change. I always get an output voltage of ~0.3 V.
According to the schematic, the output pin is connected to the ground over a resistor (RP2B) and a led (LED4). Does anyone have any ideas, where the problem can lie?
Thanks for the tip, I will check the board once more.
Can the resistor be the source of the problem? It seems that this 680 ohm resistor is being used to protect the LED. I wanted to know whether it works fine. Therefore, I checked the Eagle files (V3.0 - 328) but I could not find this resistor on it. The announced Eagle schematic on the webpage has some inconsistencies (330 ohms instead of 680 ohms). Where to find the corresponding resistor?
OK, I have found it. It is a pack of resistors, which has the part number: YC164-JR-07680RL and is indicated with 102 on the board. I would check it as well.
Hi,
After checking the specifications once again, I relalized that the pinouts of AMS1117 and UA78M05 do not fit to each other. An advise for those, who face the same problem:
There are some other parts, which have the same pinout but have less max output current than the original regulator (e.g. LT1121)
Do not try the following ones (as I did):
LT1117 SOT-223 (Linear Technology)
AMS1117 SOT-223 (Haolin)
REG1117 SOT-223 (Texas Instruments)
LM1117 SOT-223 (National Semiconductor)