Oh, what a fine device. A Classic! It gave me pleasure over so many years. The 520S is a very solid, tube-based short wave transceiver. Grace to its 6146B tubes almost nothing can go wrong... It's a great device for anybody who wants to start a Short Wave radio amateur career.
I gave it away to my local radio club since I had my Kenwood TS-930SAT and didn't need two systems. They're using it for education purposes.
Interesting pages on the TS-520S: