Ghost in the Pre OT? I Think I'm Losing It...

Old Stromburg-Carlson 3 channel tube pre (common out), scope it and losing one side of the wave.  So...focusing on the PI and OT, long story short, I am getting balanced AC signal into the OT, both sides having AC moving up and down with the vol pot.  Bad OT, right?

So I tack in a new Edcor and same result.  I am at a complete loss as to where to look for the issue here.  I feel like I'm looking at a square circle... ???

Gents, any guidance would be most appreciated.

If you have a schematic, is the output push pull?  If so, then one of the output tubes is bad.  Swap to confirm.
If it is class A out, then you have some sort of tube or biasing issue.  Can you post a schemo?
Mike

Thanks Mike,

Tubes are good: tested and swapped.  Blocking caps test good.  As I said, the signal is getting to each side of the OT primary, just not coming out.  Looks like: -^-^-^-  Maybe I should do a signal trace to confirm the signal is good, not just there.  Here's a rough schemo:


Thanks again.

is there a possible faulty joint? Also make sure the PSU section is in order...