06-03-2013, 12:51 AM
It's starting to make sense now. V501 isn't conducting because it's cut-off: control grid @ -4.5 v.d.c. Hence, no anode current, no volts on cathode, anode voltage @ +360 v. V502b, strapped as a diode, has biassed off V502a, (normally getting a pulse from the osc. to complete the feedback cct.), making its cathode -ve and thus the grid of V501. Until V502b gets going, nothing is going to happen. And it won't get going if its grid return resistor to 0v. is O/C, (which I'm sure it is), since then that grid is heavily -ve too.
Al.
Al.
