In Reply to: RE: now I am really puzzled ...... posted by vinnie2 on April 26, 2016 at 14:35:38:
"when I took it up to full mains the voltage did not come back up."
When you turn up the Variac, anode voltage "peaks" when you reach a point where A) a good amount of B+ from the power supply reaches the anode, but B) the filament hasn't yet heated to a point where the tube conducts well. As you continue to raise the primary voltage past that point, heater emission rules the day. B+ is increasing, but so is the tube's emission and current draw. Also, I'm pretty sure that the emission in a DHT continues to increase as filament voltage is raised. This is different than most IDHTs, where cathode emission has limits created by other factors, and will generally plateau before reaching full operating voltage.
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Follow Ups
- Filament Emission - Triode_Kingdom 21:31:58 04/26/16 (1)
- RE: Filament Emission - vinnie2 03:28:07 04/27/16 (0)