Hi, I once had a 442 and fixed a problem similar to yours. This was also reported by me on another forum a few years ago: (from that posting)

". I have experience with the 442 including fixing the problem you have. I bought one not working about a year ago and completely refurbished it. I then used it for a year when I got a deal on a newer model, then sold my 442.

Here is the short version
That fuse feeds the high voltage supply. I bought a CD manual from QService but gave it away with the new owner. However I still have a printout of the HV CRT section. What I found was the same blown fuse you have. I temporarily put in a 1/10 fast blow until I could order the 1/16 fuse. The scope then showed a trace after about a minute warm up. It blew after a couple of hours of use. When I finally got the service manual, I found that Q458 (? 2SC2333? NTE379?), a power regulating transistor, had been replaced before. So I ordered a replacement as well as the Electrolytic cap C458 (10uf 150V). E-caps are notorious for going bad. After replacing the Xter and cap, the turn on time went down from a minute to 10secs! And it would run for hours. (is there a place to post the schematic .jpg?)

Later I also cleaned the vertical attenuator contacts (caution, be very careful!) and some potentiometers. At one point I was having a strange problem which I traced to the polarity trigger push button switch. I replaced that but after dissecting the old switch found I might have fixed it by just pushing it in and out a hundred or so times. The internal contacts had tarnished from lack of use!

I also found some of the internal wires were breaking loose from the plastic contact carriers. So I re-soldered those. I then gently tugged on all wires and re-soldered any that came loose.
I did several other things including replacing all the large ecaps near the main power supply (Turn on time now down to 3 secs) also added a thin fan for cooling to the back.

Take lots of pictures!!!! It really helps. Also, observed all safety precautions especially those relating to the HV area. I could go into a lot more detail, but it would make a very long post.

Bob