I bought a cheap AC-DC floating output switching brick to feed the grid (+-15V gives me -30,-15,0,+15,+30V, depending on which output I ground), cheap switching power supplies to light the filament and a variac feeding a rectifier/cap. I put a voltage on the grid, light the filament, and slowly ramp up the HV. No rush here.
Some of these tubes are gassy because they are really old, even if they were never used. Some of the gassy ones are gassy/salvageable and some are just junk. In my experience, blue glow that starts to appear at less than 100V generally clears up. Then there is a purple glow that appears around 400V. That's the nasty one that hasn't cleared up for me ever.
Some of these tubes are gassy because they are really old, even if they were never used. Some of the gassy ones are gassy/salvageable and some are just junk. In my experience, blue glow that starts to appear at less than 100V generally clears up. Then there is a purple glow that appears around 400V. That's the nasty one that hasn't cleared up for me ever.
This is how other tubes behave. I had 6C4C and 807 work like that and there were no problems with them.
How high do you take the plate before your happy? There's also a bit of info out there talking about a 24 hour burn in. I won't be leaving something like that unsupervised
I use the setup to trace curves for the tubes. I run them up to 90% dissipation for each curve or up to 800V, whichever comes first. In my experience, gas ionization issues present themselves at less than 450V. My variable supply has a 1k power resistor in series to limit current in gassy tubes. What typically happens is that as I crank up the voltage on the variac, DC voltage rises until the gas ionizes, then the tube starts drawing more current and the plate voltage drops to a lower voltage because of the 1k resistor. I let it sit there until the gas clears up, then I add some more voltage and see if it ionizes again, repeating that process.
Some people recommend 24 hours without plate voltage but I haven't seen any of the old transmitter tube guides that say to do this.
Once I am confident that I don't have a gassy tube, I just start using it.
Some people recommend 24 hours without plate voltage but I haven't seen any of the old transmitter tube guides that say to do this.
Once I am confident that I don't have a gassy tube, I just start using it.
