Magnetron, I have taken the 4k7 resistor out all together, it doesn't seem to make any difference. And if I lower the 100k value, the voltage drops right down to a few volts, and if I put in a higher value, it doesn't really have an affect. Leaving out the 4k7, and using the 100k bias resistor, the output voltage climbs very slowly to about 60V dc...as if the cap is charging or something. I know I'm prob doing something daft, but what's bugging me is the fact that its a pre built pcb, so the components that I'm using SHOULD be the correct ones...hmmm.
MikeML, the voltage should be quite high...about 100 - 180 V dc going onto the anodes of a 12ax7 tube...only about 200 mA I guess