Does it mean 600v if the heaters are at 6.3v and more if the heaters are "raised" ?
Yes, though thats a rather misleading way oif putting it. The heater will always be run at 6.3v, whats important is the voltage difference between the heater and the cathode. If the heater is at 0v, then the cathode can be no higher than 600v above that. If the heater is at 1000v, the cathode can be at 1600v, and so on. remember, there is no such thing as a absolute voltage, just a difference in potential between points.
The peak inverse voltage refers to how positive the cathode can be in relation to the anode, you will never get the anode to be 6000v higher than the cathode, as it would conduct removing the voltage difference.
In the case of my amp. Its got a 1440v CT secondary winding, so we can calculate the max voltage and peak voltage the rectifier would see. On the positive swing, the voltage will peak at 1015v ((1440/2)*1.41), so the diode will conduct, charging the cap that follows up to 1015v (minus the forward voltage drop of the rectifier). Then at the negative swing, the anode is driven to -1015v, so the voltage across the diode is -2030v (1015 - -1015). So we are well withing the max inverse voltage, but as the cathode is above 600v, I can't use a heater supply that is at 0v, so I ensure I have a 6.3v supply on the transformer that is insulated for use at 1000, link the cathode to the heater supply, and its all happy.
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
