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Registered Member #3925
Joined: Fri Jun 03 2011, 10:50AM
Location:
Posts: 121
Hi,
I've built the 811A vttc, and it works! just a few questions...
i'm using 2 tubes. and at full voltage (~2KV) the plates of both tubes glow red, is this ok? the resonant frequency of the primary measures as ~250khz, how do ya measure the secondarys resonance? the coil works allright at the start, with streamers about 1.5" long (too small?) but after a few minutes the sparks get smaller, and eventually become intermittent. finally.. i am using an earth rod instead of mains earth, although idk if the earth rod is working properly, the resistance between the mains earth and the earth rod measures as 4 meg-ohms, is that ok?
Registered Member #1403
Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968
A 811A tube should not be run with red plates for too long at a time, you will shorten the life of the tube and risc burning a hole in the plate, destroying the tube forever.
Best thing to do is calculate the secondary resonance, for tuning purpose, its precise enough to get a decent tuning that you can work on with.
You should put some more effort into tuning your VTTC, adjust feedback coil position and turns to have a more gentle drive of the tubes, to avoid red plates.
Are the tubes sharing the load equal? or does one tube get red faster than the other? You might need to tap your feedback coil to give them different drive voltages.
Registered Member #3925
Joined: Fri Jun 03 2011, 10:50AM
Location:
Posts: 121
Tom Williamson wrote ...
the resistence between the 2 earths would make sence, because one is probibly several M away from the other one?
okay thx yes probably many miles, thought so :D
Mads Barnkob wrote ...
A 811A tube should not be run with red plates for too long at a time, you will shorten the life of the tube and risc burning a hole in the plate, destroying the tube forever.
Best thing to do is calculate the secondary resonance, for tuning purpose, its precise enough to get a decent tuning that you can work on with.
You should put some more effort into tuning your VTTC, adjust feedback coil position and turns to have a more gentle drive of the tubes, to avoid red plates.
Are the tubes sharing the load equal? or does one tube get red faster than the other? You might need to tap your feedback coil to give them different drive voltages.
Your grounding with a earth rod sounds fine.
ahh okay, yes i did calculate it and it is a rough match, around 300khz, is that too low for a tc?
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811A vacuum tube tesla coil.
