Hello Jeanyves. I was waiting for someone else to reply because I do not know much about what is inside mt TS-440, I don't often use it and and it has never gone wrong!
I don't understand what your problems is. Is the problem on receive or transmit?
I remember from the Yahoo group that the most common problem is the blue compound Kenwood used on early models to lock the VCO tuning cores. All the posts and files from the group are now on
Groups.io. Join the group and everyone there will understand your problem, and will tell you the solution!
PostScript - I see you have already joined the group and are getting advice