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Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
I am still in need of some good quality high voltage caps for my 12kv 60ma transformer tesla coil. On gravitymagnet.com they had a chart saying for a 12kv 60ma transformer for ltr capacitor i should use 8 in series. That would be great and all but the voltage would destroy it wouldn't it?I figured i should use 14 per string and 2 strings. The ac rating for those capacitors would be 1kvac, right? If so it couldn't stand more that 8kvac. There is no way this could work(for long).
Registered Member #146
Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055
In my experience, the single string will work, but the longevity is questionable. Definitely go with 2 strings of more caps if you can afford it, it will not only last longer, but probably survive any mistakes you make.
Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
Wow, looks like i need to make alot of money.... Around 200bucks. If anyone wants to donate feel free! Kidding...again...
Would anyone suggest doorknobs over other capacitors if your on a tight budget? I found some cheep 30kv 4700pf capacitors(doorknob) and i am going to buy them if the guy starts a new bid for more on ebay. But i do not believe he is. So i am stuck. I am building uzzors's palm sstc after i get the capacitors for the sgtc, so please don't suggest i make sstc. I already have one running of my design so i do have something working out for me. ;)
Registered Member #135
Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735
Not if the Doorknobs you're attempting to buy are Spragues. Sprague Doorknobs are Mica and are not suitable for TC work unless you plan on <300W.
You have to measure each Mica cap because they will not be the face value. A 4000pF cap may be as low as 1800pF, which means its on its way out!
The guy I bought my Spragues from a couple years back just destroyed his PT because they shorted during one of his runs. Bill even asked me if he could buy the PT he sold me to replace the one he blew.
I was a bit lucky in comparison to Bill, I only killed a brand new 12/60 Franceformer, still cost me $200 though.
So you have been warned. Micas are for DC blocking, not pulse. The will work to an extent, but once they're dead they kill your supply too.
Registered Member #477
Joined: Tue Jun 20 2006, 11:51PM
Location: Seattle, WA
Posts: 546
Arcstarter wrote ...
Would anyone suggest doorknobs over other capacitors if your on a tight budget? I found some cheep 30kv 4700pf capacitors(doorknob) and i am going to buy them if the guy starts a new bid for more on ebay.
The strontium titanate RF dooknobs might do ok. I've heard of people using those in SGTCs. The usual problem with doorknobs is overheating and literally "frying", AFAIK. These days, they're mostly considered fodder for Marx generators and VTTCs. A friend of mine built a HUGE MMC out of more than 100 of those little 500pF Sprague mica doorknobs (usually green in color) and attempted to use it with his pole pig coil and ARSG. He was blowing a cap every couple of seconds and evenrually decided he'd better stop and save the rest for some other non-Tesla project.
Of course, nothing is "cheaper" if it immedialy blows up. Then you're back in the same place you started from with a negative balance!
EDIT: Hehehe...funny...Hazmatt jumped in while I was typing the above...guess that's two strikes against the Spragues!
Registered Member #1107
Joined: Thu Nov 08 2007, 10:09PM
Location:
Posts: 792
At this point the cde sampling service is going to be your best friend because they will send you 10 free caps therefore saving you about 30 bucks but hey 10 is better than nothing.
Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
teslacoolguy wrote ...
At this point the cde sampling service is going to be your best friend because they will send you 10 free caps therefore saving you about 30 bucks but hey 10 is better than nothing.
Oh, ok, that is how it works! Can you tell me how to do it? Thanks everyone from saving my money by telling me what not to use :). And thank you teslacoolguy.
Update: Apparently the 942C20P15K-F are only rated for 500vac....
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Question about 'Geek Group' capacitors.
