Apply some known signal to the 475 scope input, set the coupling to AC and the Volt/div to the appropriate setting.
Check the 200 MHz position of the switch, as that is straight through and does not go though any filter components. On the good scope you should see identical signals at A input and G output. Similarly the signal at B input and H output should be identical.
Signals at A input and B input should be complementary (equal except inverted polarity.) If not there is a problem in U370 or before that.
With the switch pushed and held in you should see, with the good scope, trigger signals at outputs G and H. If yes, but not on the 475 screen, there is a problem with the delay line or subsequent stages. If no, and the outputs of U370 are not OK, problem is likely before the U370, ie at a point before the trigger signal is tapped off.