Push-pull interstage xfmr

I'm working on a new project...an audio amp similar to the Western 
Electric 7A.
http://www.nutshellhifi.com/library/7Apix.jpg

Having trouble with the PP output stage....apparently overlooking 
something butt-simple.

In trouble shooting I came across something I find strange.  I'm using a 
single ended stage feeding into the PP grids using a Hammond 124A xfmr. 
  With both of the PP output tubes pulled and using high z fones to 
'listen' at the grid pin on the socket the volume/tone is drastically 
different between the two.  The xfmr ohms out at 840 and 720 ohms from 
each end to CT which doesn't seem unreasonable.

I also note that with one of the PP tubes in place and listening to the 
grid on the empty socket I'm getting some gain.  If I put the tube in 
the other socket I get an oscillation.  Wiring is somewhat symmetrical 
and if I switch the grid wires the symptom follows to the other socket.

Whats going on here?  Do I have a bad xfmr?  Anybody have a 124A xfmr 
handy to confirm the resistance readings?

TIA,
Bill
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