Soviet tech tree question

[harlikwin667]

I'm sorry if this posted somewhere and somone can point me to it. But I can't build heavy industry or 1937 level electronics. What are the prereqs for these techs in core?

Also I can't build industry as the SU (do you need heavy industry to do it?)

 

[baylox]

As Soviet Union, you currently need 1939 Heavy Industry to access 1937 Electronics and to build IC. 1935 and 1937 Heavy Industry are not available (and do not become available), but all such techs after 1939 do.