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Registered Member #514
Joined: Sun Feb 11 2007, 12:27AM
Location: Somewhere in Pirkanmaa, Finland
Posts: 295
Maybe you are simply not getting enough feedback on lower powers. It might be very destructive for your bridge if the problem doesn't go away at higher powers.
Few things to try:
-Make sure your ground is good. -Try adding some more turns on the CT -Make sure your clamping diodes aren't damaged, or any other parts for that matter.
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
Woot, it lives! The trick was to add a resistor across the CT (I've used 4k7 resistor). Also it helped removing turns from the CT, not adding. I'm a little worried the CT could raise the supply voltage for the 74hc14, I think I'll zener-clamp the CT just to be sure. This is a discharge I get with 160V to the bridge and 8 primary turns:
I'll also be making a new resonator with more turns, this should help too.
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
WhiteArc wrote ...
Whats the arc length, it looks like 1-3 inchs?
That arc is not big, about 1", but it tells that the coil is working well. No noticable heating of the fets with the fres around 600khz. I'll be removing turns from the primary until the fets start getting warm, then as time allows I'll wind the new (lower fres) resonator, looks like a lot of fun is coming
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
well, with the new secondary which is 2" taller (total 10" wingind length) than the old one and has ~2x the turns, the spark length didnt increase much. Previously it was something like 2" and now it is 3" at most.
I'm using 4 primary turns with 160V to the bridge (with irfp250's), I think it's time to upgrade to 320V and irfp460's.
IIRC Steve Ward got 7" sparks with 4 turns and 160V, I don't know what the problem could be (if there is any).
Right now I have the primary just wound around the base of the secondary, should I make different primary for better results?
As for topload, should I use any? or is the nail I'm using now all right?
Registered Member #618
Joined: Sat Mar 31 2007, 04:15AM
Location: Us-Great Lakes
Posts: 628
Thats odd JM, Cuz I too have built this and I'm running 160v of fullwave rectified, with out a topload I get giant 9-13" arcs, no idea what I get with a top load since I was more afraid of my antenna arcing to the topload. =( Heres the video of the arcs
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
WhiteArc wrote ...
Thats odd JM, Cuz I too have built this and I'm running 160v of fullwave rectified, with out a topload I get giant 9-13" arcs, no idea what I get with a top load since I was more afraid of my antenna arcing to the topload. =( Heres the video of the arcs
It says the file no longer exists
How big is your secondary and what type of primary are you using? and how moch power?
I'm drawing maybe 100W of power, with the interrupter at ~40-50% on time. The transistors are stone-cold on their little heatsinks, something must be limiting the power here but I have no idea what it is
Registered Member #95
Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308
jmartis wrote ...
I'm drawing maybe 100W of power, with the interrupter at ~40-50% on time. The transistors are stone-cold on their little heatsinks, something must be limiting the power here but I have no idea what it is
Coupling is a major part of determining power draw. I found Richie Burnett's site very informative.
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