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Registered Member #2899
Joined: Wed Jun 02 2010, 06:31PM
Location: Deinze, Belgium
Posts: 255
With the 811a and a 10 nF cap and classic circuit (I build several of them) but this time with a little coil it won't work! I think it is the coils, but what can I do? Help!
Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061
Yes, check the phasing. Also check that the tube isn't damaged, it should NOT glow blue unless being severely taxed. A little glow is OK but bright blue means it could be gassy.
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
Hi, you really do have 10 nF of capacitance there? Way too much, go for something like 1 nF, RF ceramic for the best result but a string of MKP/FKP caps works too.
The obligatory question: Did you calculate the resonances and tune the coil with primary taps?
Registered Member #2899
Joined: Wed Jun 02 2010, 06:31PM
Location: Deinze, Belgium
Posts: 255
Dr. Dark Current wrote ...
Hi, you really do have 10 nF of capacitance there? Way too much, go for something like 1 nF, RF ceramic for the best result but a string of MKP/FKP caps works too.
The obligatory question: Did you calculate the resonances and tune the coil with primary taps?
Edit: What is the supply voltage?
I can not go lower than 10 nF, I have 5 47 nF capacitors, it is a surplus... And I did the calculation, but have no taps on the coil. The supply voltage is 1200V DC.
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
Well, for 1.2 kV 10nF might be tolerable, still too much, but the coil should work anyway. Make the primary coil tappable, when a VTTC is out of tune, the output can be almost none.
Registered Member #2899
Joined: Wed Jun 02 2010, 06:31PM
Location: Deinze, Belgium
Posts: 255
Dr. Dark Current wrote ...
Well, for 1.2 kV 10nF might be tolerable, still too much, but the coil should work anyway. Make the primary coil tappable, when a VTTC is out of tune, the output can be almost none.
What kind or type are the capacitors?
47nf 3000V, those white-ones. Thank you, I will try to tune again...
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I can not get this little coil working.
