In which Wimbledon womens final or semi-final (we think) late 1970s to early 1980s, did the umpire have problems with his microphone?

My grandfather was a sound engineer at Wimbledon, and my family all remember rushing to look at the TV to see him fixing the umpire’s microphone.
We’re trying to find a recording of this incident, which lasted a few minutes.

To the best of our combined knowledge it was the women’s final or semi-final in the late 1970’s, possibly early 1980s – most likely 1978-1980.

We’ve found a couple of complete matches on the The Greatest Championships playlist at the official Wimbledon channel on Youtube (1978 and 1980 womens finals, Evert/Wade semi 1977, and Navratilova/King quarter 1980) but it doesn’t seem to be any of those.