Google Sheets IF, ISBLANK etc

I'm trying/failing to write a statement that returns a value of "Broken" if -500 is found in a cell, if the cell is blank then I want it to return "not installed" and then anything else i want it to return "OK" -

It feels as though i'm nearly there but strugggling - any help is greatly appreciated.

Here is what I have so far:

=IF(ISBLANK(E2),"Not Installed",IF(find("-500",E2),"Broken",IFERROR(find("-500",E2),"Correct")))