In this video I repair a 500MHz TDS620B oscilloscope and show how to hack it up to a 1GHz TDS680B.
This mod will work for many scopes in the TDS500/600/700 series.
https://w140.com/tekwiki/wiki/TDS500
https://w140.com/tekwiki/wiki/TDS600
https://w140.com/tekwiki/wiki/TDS700