Interesting; looking at your last-released cct. diag., the only 1 nF caps. I can spot are C505 and C511. C505 has only one connection to the transformer; other 'leg' of C505 goes to V503, and C511 doesn't connect to the transformer at all. I suppose that it is just possible that one 'leg' of C505 is wired to a dummy tag on the transformer, but considering the new / additional R in the cathode of V501 and the valve-type changes, I suspect that this board is a new design: hence, your last-released drwg. is N/A; hence, your reverse-engineering attempt - which I hope is revealing.
Al.
Al.
