Martin and Aardvark, here's a large advance, at least for me! I replaced the 4.2.7 board and did all that is normally done at this point, plus paid very, very close attention to all things related to selection and installation of the proper firmware--- and it finally worked. Actually did a 1 hour print which came out perfectly, including new entries on the display panel. A small accomplishment really, but a stellar achievement for me, after such a ' long and winding road'! The only identifiable fixes were the broken thermistor lead and, I am sure, the correct firmware plus tightened connections, etc. What kept me going was the support and advice you lavished on me--absolutely essential. Thanks so very much! We'll see how well I handle my next disaster. Keep up the good work; it means a lot!