Schematic for department of commerce limiting amplifier

I picked up a type ca-1396  limiting amp ..  anyone have a schematic?  Thanks

all varieties are very similar, there are several posted around here in various places

Thanks Doug.    You have some interesting preamps for sale?

What's the full tube line-up?

tubes are 6sf5  6sn7 6h6 6sn7    two ob2 and a 6x5.  I got it working today.  The unit always  in comp mode ,but the meter switches between input bypassed and comp. Inside is a threashold adjustment .  The input wont take muck more than -35 db input and it puts out +20 or more .Frequency response  rolls off at 4k.  Output impedance is  600 ohms i assume?  It has  split coil centertap . Input is 25 ohms or 600?  Id like to find a quieter tube for the 6sf5 spot.

maybe ill make and adaptor to run both halfs of a 12ax7 in parallel  for the 6sf5 tube sub 

I've never had luck finding a quiet 6SF5 or 6F5.

I made an adaptor  .  I ended up using a 12bh7 with both sides in parallel.  Its good but  its still a bit hissy .  I can find any low noise 6ns7s in my stash.  I think think  theres a good Russian sub for those.  Makes quite a distortion box when pushed.

Maybe changing out the old plate resistors would help.

I don't think this is a variation I've come across.  Your pic at GS looks like all the other 1950's models rather than the 1940's models.  Any inside or rear pics? 

ill take some now

serial number 12

Is the 6SF5 wired as a phase splitting input stage?  Or is this thing entirely single ended? 

I haven't even traced it yet..  HAHA.  l"ll  check  and see if it has an output from the cathode  too.

3.9k and a 2uf cap on the cathode of the 6sf5

I'm glad the transformers are working.  I dug this out of a pile of junk at a ham fest .  I will draw up a schematic soon

Cool.  Doesn't sound like the one I drew (posted here somewhere) will be much use, but might be worth considering it. 

I have that one . I'm curious if they all have a distorted type sound to them.  When I get home I'm gonna check for leaky bypass caps.

I've worked on a half dozen different models.  They all sound like distorted telephones.  The band-limiting is very much about hiding the distortion.  The vintage piece for the person who has everything! 

Good to know.  I dont want to get crazy with it.  Its built like a tank, so one assumes it should sound better. Not a vocal comp.  Maybe electric guitar or drums.
  the oil caps are still working good.