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Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068
Some things to remember:
1. Be sure you use a break-out point.
2. If no output is detectable, try reversing phasing.
3. Use a strike target about a few inches way (tied to GND) to help pull the arc so you can see it better.
4. Try routing the interrupter cable away from the coil and keep interrupter control as far away as possible. Sometimes, interference can cause the overcurrent light to illuminate.
5. Use a 50 foot extension cord (or similar length) for the resonator power. This will reduce the arc length, but will also help act as a ballast while you initially troubleshoot and run your coil.
Registered Member #7267
Joined: Tue Oct 16 2012, 12:16AM
Location: Detroit, Michigan
Posts: 407
The buzz in the video is coming from the GDT and is directly correlated to the modulator signal as you are probably aware already. It is perfectly normal. from the looks of it, everything is fine. Could just be a tuning or phasing issue like EVR said before.
Registered Member #9471
Joined: Thu Jan 10 2013, 09:17PM
Location: (39.41895551215511, -76.29627227783203) Grid square:FM19UK
Posts: 23
Physics Junkie wrote ...
The buzz in the video is coming from the GDT and is directly correlated to the modulator signal as you are probably aware already. It is perfectly normal. from the looks of it, everything is fine. Could just be a tuning or phasing issue like EVR said before.
Yeah I get that but during high power testing I had no output and blew an IGBT. We are still coiling the new secondary. Younger two kids are in bed and Liam and mom are taking turns on the coil jig.
Registered Member #7267
Joined: Tue Oct 16 2012, 12:16AM
Location: Detroit, Michigan
Posts: 407
No output and blown igbt sounds like the GDT is either wired wrong or phased incorrectly. Whenever I've accidently wired my GDT's wrong, it ALWAYS results in the igbt getting blown the instant I apply power to the bridge.
Registered Member #9471
Joined: Thu Jan 10 2013, 09:17PM
Location: (39.41895551215511, -76.29627227783203) Grid square:FM19UK
Posts: 23
The board has been to EVRs shop twice for help and came back with a clean bill of health.
We finished the new secondary and went through low power testing cleanly
under high power testing I was getting sparks out of the bottom of the coil from the screw I used to attach it to the enclosure. I removed that screw and backed up to the beginning of high power testing Ran it up to 50% PW 50%prf with no output so I undid the enclosure and reversed polarity and set everything back up. Turned it back on and ran the PRF up to 50% and heard buzzing. I ran the pw up slowly and it was sounding good like I woud get sparks any second. Figured I would get some output and then go for tuning the primary. Right at 50% PW the IGBTs popped again and so did the fuse on the coil power.
Looks like Liam has to present without a working project tomorrow.
Registered Member #7267
Joined: Tue Oct 16 2012, 12:16AM
Location: Detroit, Michigan
Posts: 407
I'm really sorry to hear that the polarity was probably right the first time since you got sparks on the screw. What are you using as a breakout point. And do you have an oscilloscope?
Registered Member #9471
Joined: Thu Jan 10 2013, 09:17PM
Location: (39.41895551215511, -76.29627227783203) Grid square:FM19UK
Posts: 23
Physics Junkie wrote ...
I'm really sorry to hear that the polarity was probably right the first time since you got sparks on the screw. What are you using as a breakout point. And do you have an oscilloscope?
PJ, You and Ben have tried to be helpful, and I thank you. The breakout point is a piece of copper wire scrap from chopping the 3 prong power cords that EVR sends in the kit. its taped to the top of the toroid with the same foil tape that EVR suggested to wrap the plastic toroid with. There is contiunity from the bottom of the coil to the breakout point. No, I do not have an O-scope. Not a common houshold tool, and I don't know anyone who has one either. I'm not in a financial position to go out and get one.
I'm pretty angry right now and trying to focus on my own fault in this so I will not say anything unfair.
I'm a military guy and Liam bore the brunt of my military time. He was three when I went in and when I transferred to reserves last year he was already a pre-teen. This was a fathers attempt to connect and compensate for moving around the country and too much time spent on the other side of the world. I threw a bunch of money at this, probably out of guilt over those things. It really hurts that I've failed him here. I suppose I bit off more than I could chew - Dans website states that this is not a novice kit and I am definately a novice with this stuff, but I'm a pretty sharp guy and I thought I could handle it.
I guess it will be up to Liam if he wants to continue with the project. Right now I want to take it to the gun range and put holes in it.
Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068
Sorry to hear you were unable to get your coil working. As you stated, i checked the boards twice and everything looked great - gate waveforms were properly phased and looked proper going into the IGBT gates and the modulator was testing properly.
I can understand your frustration. I recall the first several DRSSTCs i built almost 10 years ago (has it really been that long???) were the devil to get working.
Anyways, i don't think you should abandon this project. You guys put a lot of work into it and i really want to see you finish it. From everything you describe i think you either have the phasing set improperly on the current transformers and/or the tuning isn't set quite right on the coil.
Is it possible if you can email me a photo of what the primary coil looks like and how the primary wires are coming off it?
Also, you did say you had a secondary failure before and had to splice the wires together for a repair. This could be the cause of the problem as well. Even though the secondary will have continuity with an ohmmeter, the splice point can act as a singularity and irregularity in the impedance and possibly change the characteristics of the resonant circuit (i.e. making the resonant frequency much higher etc...) although if the splice point is flat and neat, this usually isn't an issue.
Anyways, i want to help you get this running. Contact me via our support email again, and i can send you out some new magnet wire and IGBTs so you can rebuild your secondary.
Don't give up yet!!! This *IS* a challenging kit - its not easy by any stretch of the imagination. You're almost there!!!
Registered Member #9471
Joined: Thu Jan 10 2013, 09:17PM
Location: (39.41895551215511, -76.29627227783203) Grid square:FM19UK
Posts: 23
Dan,
I bought a 1/2lb spool of 30ga magnet wire and we re-coiled the secondary last night. we were up till almost midnight when we got our last failure. I had to get up at 0400 for my -still very D.o.D- job so I'm a bit worn down.
I'll let you know later how Liam's day went when I get home.
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
This talk of sparks coming off screws makes me think there is something wrong with your grounding. That might also explain why the coil wouldn't oscillate properly. Can you tell us more about the RF ground system you used for the tests? What did you connect the base of the secondary coil to?
Sorry to hear you couldn't get it working in time BTW! :(
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the polarity was probably right the first time since you got sparks on the screw. What are you using as a breakout point. And do you have an oscilloscope?
