Defective generator, problem Nano V2

imho, working plan.(i have not device, and see only schematics and photos)

  1. discharge yourself touching with finger some ground point of your device. device must be turned off.
  2. put your finger on the chip which was hot (U9?), turn device on and wait, if it will be warm or hot. is warm/hot - turn device off and visually search for shortening from U9 output pins and device generator output jack. if it is hot - it is problem. may be problem is in jack(remove any cable from this jack-cable can be shortened too).
  3. if U9 is not warm or hot(without cable in generator output jack and with) - try to measure some battery with this oscilloscope, to prove that oscill. part is working. if you cant measure proper volts - oscill part is not working, but generator seems good.
    4.report results here.

PS. looking at the scheme, i see that they have not any resistor in serial to limit output current of u9. so if output is shortened - it can damage u9? Also, it is obviously wrong to drive some speaker with generator output. there must be resistance about 100 or greater omhs in serial, to limit output current. I propose to make this mod to everybody to save U9 output.