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Registered Member #10052
Joined: Thu Feb 07 2013, 11:31PM
Location: Overland Park, Kansas
Posts: 78
Update: I've got the MMC strung together. 24 of the CDE 942C20P15K-F caps for 225nf at 8kvDC and a theoretical peak current handling capacity of 2.4kA. I hope heating won't be a problem, I don't plan to use fans here.
I don't like the idea of reducing the current carrying cross-section of the copper busses by drilling holes for mounting, so I think I'll solder on some big copper lugs to make connections, and use zip-ties to hold everything down. It doesn't have to make it through an earthquake, just has to stay put.
Not sure quite how to cool this. Other than a gallon of thermal paste, just sticking a fan to the back seems like there would be parts of the heatsink recieving uneven or no airflow. Wether or not this matters too much, I'm not sure. It'll work out somehow.
I was looking for either a laptop-style tangential blower, or a crossflow squirrel-cage type blower to put at one end and just blow through the heatsink, rather than directly at it. However, I can't find anything that would fit.
Registered Member #7267
Joined: Tue Oct 16 2012, 12:16AM
Location: Detroit, Michigan
Posts: 407
I also bought four of those caps for a drsstc i'm building now. I've tested my 240V voltage doubler to 760V using the caps in a 2x2 parallel x series config. So they have tested fine for me and I'm sure they will work for you! I did find that they were not new like listed, one of my caps came with a charge on it! they had lots of signs of ware and tare on them (dents and scratches), but anyhow, I think they will do the job. Can't beat them for the price
Registered Member #10052
Joined: Thu Feb 07 2013, 11:31PM
Location: Overland Park, Kansas
Posts: 78
Agh.
This is getting expensive!
I've been trying to test the board I'd thought I'd managed to resurrect with new IC's, but it wasn't so simple.
Made a short video (will give you an idea where I am with this board)
Using my function generator to supply a 2v p-p sine wave to the feedback input at 75kHz, and getting strange intermittent results.
If I were on par with most of you guys with my diagnostic skills, I would poke around the board, figure out whats wrong, fix the problem(s), and have a beer.
Unfortunately, I'm not. The boards have seen a lot of noobish mistakes, and are pretty worn out, with separated pads and delaminated traces.
Registered Member #146
Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055
Bummer to hear about your boards having some problems. Dont feel too bad, i still manage to destroy some PCBs now and then, so consider it a learning experience and try again with confidence until you get it right. On the other hand, learning how to make a really f'd up board work by patching it up with 30awg teflon insulated wire and tweezers is a great skill to develop .
Anyway, i just watched your video and the problem is that you are using a scope probe to connect your function generator to the board, and that just doesnt work. You need to get a generic coax cable with a BNC connector on one end and feed that into the CT input. With the way you clipped it to the scope probe, youve added like 10M impedance between the sig gen and the input to the board, and it looks like its just letting a tiny bit of noise through, enough to cause the CT comparator to oscillate some.
Registered Member #10052
Joined: Thu Feb 07 2013, 11:31PM
Location: Overland Park, Kansas
Posts: 78
WOOT FIRST LIGHT!
MIDI test video here with everybody's favorite Van Halen > (skip the Beethoven)
Yeah it was all a learning experience.
I actually managed to get the coil working one the board to the left, but only intermittently.
The UD2.5 came in yesterday, got it put together with some RAM heatsinks on the regs and a cooling fan.
Right now the OCD is set at 400A. I'm not sure if I've got it tuned up very well, but its pushing out arcs no problem. Running about 140 volts on the bridge so far (yeah lots of on time!).
QUESTION:
Right now the coil is grounded to a 6' ground rod just outside. However, I'm going to be exhibiting at lots of indoor events, and won't have access to a nice RF ground.
I've been wondering about a 10' by 10' chicken wire "counterpoise" pad, directly under the coil/exhibition area. I see some surfaces offering insufficient coupling to the pad, and letting it float around at secondary-level voltages wreaking havoc. However, I don't have any experience with this.
What do you guys do at teslathons, or in gymnasiums?
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