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Registered Member #2318
Joined: Fri Aug 28 2009, 01:22AM
Location:
Posts: 33
So I just finished my first dual 811a coil. Everything was working fine except my sparks were topping out around 5 inches even with it tuned as well as I could tune it. I tried installing a level shifter using a mo diode and cap, and the sparks increased to almost 9 inches! But with it hooked up this way my plates are turning pretty orange. Not totally orange, as in the periphery of them remains cool, but a good 2/3 of their surface is consistently orange. I know ideally they shouldn't turn red at all. But it's this too red to run this way repeatedly? If I left it like this how long will my tubes last? I have a fan on the tubes to cool the if that helps. I just need some advice since this is my first vttc. Thanks!
Registered Member #2318
Joined: Fri Aug 28 2009, 01:22AM
Location:
Posts: 33
Well I answered my own question. It ran great for several minutes, but then one of the tubes started emitting a purple glow and the streamers died. So I guess I ruined one of my tubes. I know I probably shouldn't have been pushing it so hard, but those streamers were beautiful. I couldn't unhook the level shifter and reduce them again.
I know they are a lot more expensive, but if I were to replace the tubes with 572b's, could they withstand the doubled voltage my MOT is putting out, assuming everything else was left the same?
Registered Member #2318
Joined: Fri Aug 28 2009, 01:22AM
Location:
Posts: 33
So since I ruined my tube, until the new one arrives, I took the coil apart to check the resonant frequency of the primary and secondary to see how well they matched from trial and error alone.
I just received a new oscilloscope, the DSO Nano v3 with Benf firmware. I had checked the fres of my secondary earlier with an old benchtop scope, and got a value of 640khz (which honestly seems too high for the coil). I used JavaTC to calculate the fres of said secondary and it gave me a value of 430khz, which intuition would tell me is closer to the actual value than 640khz.
So I tried again with my new scope and the primary coil is resonating at 500khz (or so it seems, still trying to get the hang of this tiny scope). I couldn't get a good reading on the secondary however. The frequency just kept jumping around and there was no real visible peak. I'm not sure if the cheap probes it came with are the issue, or the scope itself, or operator error.
Anyone that can provide any ideas on what I might be doing wrong would be awesome. Thanks!
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Level shifted dual 811a vttc. How red is too red for the plates?
