Repairing Bootloader Arduino Nano ATMega328 CH340G Clone

Hi;

Whilst uploading a sketch program to one of my Nano copies my Mac suddenly powered off. When I rebooted it the Nano USB/Serial Port was no longer recognised.

All of my other Nanos (same type are fine).

Today I decided to try and get this broken one working, I followed this guide:

https://learn.sparkfun.com/tutorials/installing-an-arduino-bootloader

But I have encountered several errors.

The first error was this one:

stk500_getsync(): not in sync: resp=0x15

After Googling this error I found this solution:

Placing a 10uf Capacitor between Reset and 5v then got me past this error but then led me to this error:

avrdude: Yikes! Invalid device signature.
Double check connections and try again, or use -F to override
this check.
(as stated in the guide)

I amended the avrdude.conf file as described here:

http://forum.arduino.cc/index.php?topic=58670.0

But I still get the same error.

Any ideas or is this toasted??