Only four screws marked “D”, “J”, Blank, “A”. And I don't see any clues in the schematics. When I got the thing, there was a bar between “J” and Blank. And “A” had a piece of broken wire, like maybe someone had an old antenna and just cut it off.
Trying to get it to work, I've tried every combination of the four screws with a “T” type FM antenna. When I plug it into the “D”/”J” combination, I get some weak FM stations. They all seem blended and tuning the radio doesn't seem to actually tune anything. The tunning only makes the blended FM stations slightly louder of quieter.
First, "A" is for an external Broadcast A
ntenna. It just provides some coupling to assist the internal loop if so desired. If the AM broadcast band is OK as it is you can just ignore this one.
Originally there was a link on the blank terminal. If it is there you won't need to connect it to anything if the T type FM antenna is a folded D
ipole with a twin-lead feed to the radio (this is pretty common). Basically connect one lead to D and the other one to J. This provides the input to the FM antenna coil.
If you don't have a dipole type antenna with two connections you basically J
umper the blank to the J (the bar you were talking about) then attach a single wire antenna to the D terminal.
The fact that things are not working well may be due to other problems including most likely an FM local oscillator that is not working. I would test or try another 12AT7. A tube that tests good may still not work in this stage, but a tube that tests bad probably will not work.