Have I stumped everyone???  Surely not!

Just finished up wiring on a Hey What 504.  Slowly applied power with variac no smoke.  Hearing a strange buzzing out of the OT.  When I hook a speaker i hear loud squealing from speaker.  I'm assuming oscillation.  When I disconnect the to input wires from the phase splitter from the out put tag board it all quits.  No sound from the OT.  Wiring diagram leaves alot to be desired!  Does this design use grid stopper resistors?  I have one small black wire from the output tag board at the end where the OT sits.  It is not connected and am wondering if it might be the feedback connection.  I can send picks if needed.  This came half wired and I'm finishing.