When I lost the sound on my ChangHong TB, eventually I found that it had defaulted to the lowest possible sound level. I found that out by pressing the up button for sound on the remote and voila! the sound started coming back on again.
Success! Before I saw your Update just now Charles, and several days back but it is party time right now, I followed your Safe mode instructions yet again. This time the MBP had been turned off over night. Fourth time lucky! Although I'm guessing that some of the earlier attempts at repair had helped things along. So now I'm avoiding doing anything with the MBP to make the fan labor and it continues to work fine. Back home in a couple of days and installing the new fan will be on the early agenda. Thank you everyone for you advice but especially Charles whose advice contained the solution!