imho, working plan.(i have not device, and see only schematics and photos)
- discharge yourself touching with finger some ground point of your device. device must be turned off.
- 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).
- 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.