FWIW, I am looking for the same information. There is a Technical Manual for this which I'm sure has a schematic, title is NAVSHIP or NAVSHIPS 91905, published in 1952. Also, the AM-413 came in several revisions so there is an AM-413, AM-413A/G, AM-413B/G...AM-413F/G.
This compressor was also supplied as part of a radio beacon set designated AN/FRN-24, whose associated tech man is NAVSHIPS 93291, might be a schemo in there too.
In virhistory.com/navy/manuals I found this:
http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&ved=0CDEQFjAC&url=http%3A%2F%2Fwww.virhistory.com%2Fnavy%2Fmanuals%2F92675%2F92675-04.pdf&ei=B1CKUv62A4vBtAabwIGQCw&usg=AFQjCNEwAK06UlBnUln4a57CTmgNk1c0Vg&bvm=bv.56643336,d.Yms
bottom of pg.5 starts a discussion of the AM-413 compressor with some helpful tidbits... no schemo though.
It mentions that the 413 "has a fixed compression circuit which provides constant level output for signals -30dbm or less. The 413-A (AM-413A/G) has a variable compression circuit which will provide a threshold of compression which may be varied from -30dbm to around -8dbm of signal input." "...the level control knob setting determines the maximum output."
My tech has been working on one of these units but has been having a difficult time figuring it out as this is not a usual circuit.
If anyone has a source for more info or even better a schemo, please let me know! Thanks!
