My seller has agreed to supply me another tube, on the presumption that the first has failed. This may not be the case, and if I discover otherwise I will return the spare, of course if I cant make either work I will have to return both.
A few thoughts on possible issues, other than complete failure -
1. Some tubes dislike certain current levels. A higher anode resistor may be required to get this tube to work;
2. Perhaps 400V is not enough, or maybe too much? Although if too much I would have expected it to avalanche. Characterizing it on a variable HV supply might find a working operating voltage. Available data shows 360 to 440V, and I have heard mention of successful operation at 440V.
3. Capacitance. Although too much shunt capacitance can kill tubes, most have an inherent capacitance of about 5pF - this tube being so tiny is 1pF. Perhaps a little extra capacitance will give it a charge 'kick' to help it to ionize.
Ive now received the 100Ω precision presets to allow me to properly control the 555 timer based HV supply. I will modify the Cockcroft doubler on this with an extra stage, to allow me to reach higher voltages. This I need to do anyway, as I also have a MST-17 tube coming, that requires 1600V!
No comments:
Post a Comment