Hydrophone issues - RFB

[I'm goin' down]

RFB - At the sonar station there is a button on the HUD that says "hydrophone normal sweep." When I push the button nothing happens. What is supposed to happen? I am in a Porpoise in early 1942.

Also, it seems that my sonar team might have hearing problems. Often I can see a destroyer from periscope depth but do not see the hydrophone light or hear them? Is it the hydrophone, the sonar team, or me?

[AVGWarhawk]

Normal sweep means the sonarman will just keep sweeping until he hears sound. As far as deaf and dumb, the sonarman is just that, deaf and dumb. Stock related issue I believe.