I had a repair job where the lady was a cleaning fanatic. When I pulled out the chassis she went bonkers apologising for the dusty insides of the tv set. The main thing about doing a repair was to clean the tube and the safety glass. In those days the crts didn't have the safety glass bonded to it and cleaning the tube and the back of the safety glass always made a major improvement on the picture and a good impression on the customer.
John