Problem with bad chinese arduino nano (auto reset every 2 second when turned on)

Using Arduino Installation & Troubleshooting
#1

Hello there.

I have a chinese arduino nano (costed 2$), i've been using it for half year, and it's dead last week, after investigating, the schottky diode (+5V Auto Selector) was dead, and i connect both connection with jumper (replacing the diode with jumper instead of schottky didoe), after that it turned on, and i can use it again, yay!~.

but in a short time another problem comes out, when it's turned on with USB, the regulator was very-very hot, after a short investigation it was caused by 100n died capacitor between vin and gnd, so i remove it, everything normal again, after uploading 2 program, another problem comes again! (the real problem) , after uploading program and restart it (turn off&on) my arduino was auto resetting when powered on!, and always auto reset, the reset was like a blink, it's auto resetting every 2 second, it makes me cant upload any program anymore.

and my gnd on each other side are not connected!, and when i connect it, the regulator becomes so very very hot (like on the first problem), and it's still on and not shorted.

because i've give up to repair it myself, i came here to get a help.
and i still want to use my old nano instead of buying new, but if there is no way i can do, i will really give up and buy new one instead.

thank you for the reply.

#2

Remove the regulator - that's probably shot (and if it wasn't after the initial incident, it probably is by now...)

It's not used when powered from USB anyway, and you've jumpered around the schottky and removed the input cap, so using external power is out of the question.

Unless you're saying you're using external power right now after jumpering around the schottky diode, in which case no wonder it's not working (the power supplies will fight with eachother, resulting in either the port shutting down, the regulator getting hot, or some other variety of power problem). If you want USB power and external power on Vin/Raw to work, you need the diode (and the input cap you say you removed too)

I'm not sure which grounds you're saying aren't connected - but they probably should be connected.

#3

DrAzzy:
Remove the regulator - that's probably shot (and if it wasn't after the initial incident, it probably is by now...)

It's not used when powered from USB anyway, and you've jumpered around the schottky and removed the input cap, so using external power is out of the question.

Unless you're saying you're using external power right now after jumpering around the schottky diode, in which case no wonder it's not working (the power supplies will fight with eachother, resulting in either the port shutting down, the regulator getting hot, or some other variety of power problem). If you want USB power and external power on Vin/Raw to work, you need the diode (and the input cap you say you removed too)

I'm not sure which grounds you're saying aren't connected - but they probably should be connected.

i forgot to say this.
Yes, i use an external power supply (2 cell li ion on series) and the battery accidentally shorted and it's created a smoke on the atmega328! (but i still can use it), after that the capacitor was dead, maybe the regulator too.
but i dont use 2 supply at that time, i'm only using a battery to power on my arduino nano at that time which is connected to vin and gnd.

#4

I would not waste more time trying to get it working with external power. It should work on just USB (and if it doesn't, remove the regulator and it probably will).

Get a new nano if you need to do work with external power source.

#5

Solved by myself!.
it was bootloader problem, i reburn bootloader into the nano and now it's working!,
but the regulator was dead, the VIN and regulator gnd was dead

#6