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Registered Member #56
Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445
the digikey site is quite unreliable, just check back in a minute and it will work fine.
From the looks of it they only have the 940c series, no 942c's to be found on the site
The normal place (rell) has the minimum order of 52 caps, so we may need a few more people to get this off the ground. If necessary I may be able to buy some for myself. McFluffin also seems interested.
The only problem I see is that both the normal and Pb free ones are listed as 'on order'... I remember someone saying that meant that they were just waiting for someone to place the minimum order before they buy more...
Registered Member #119
Joined: Fri Feb 10 2006, 06:26AM
Location: USA
Posts: 114
942c20p15k... 0.15uF, 2kV, a little over $2.50 each it seems. For my 10.5kV tesla coil, how many of these might I need? It sounds like that might get expensive very quickly from the 100 capacitor MMCs I've seen. Of course, these seem to have pretty high capacitance compared to others I have seen, so maybe I wouldn't need too many. From what I understand, a string of 10 of these guys making a 3J capacitor rated for 20kV isn't bad. Don't want to get a full discussion in sale/trade, just a rough estimate on how many I might need.
Registered Member #56
Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445
what current are you running? To calculate the value for your mmc you need to know voltage and current of the power source, then you can calculate what the resonant value, and then go to about 1.5x that
For a 30ma transformer you are looking at about a 7.5nf resonant cap... So if you use a string of 15 you could tak on whichever cap you need for good tuning... Or just use the ones you happened to find
Registered Member #119
Joined: Fri Feb 10 2006, 06:26AM
Location: USA
Posts: 114
Odd how things go, but I managed to get 51 1.6kV .027uF caps today. They seem to be working fine for some simple spark gap tests(I made 3 strings of 12, going to make a fourth). I might just see how things go with them before I pitch in for the group buy. Of course, if my calculations are correct, thats only about 14nF.
Registered Member #146
Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055
For a 30ma transformer you are looking at about a 75nf resonant cap
You are off by a factor of 10 . 7.5nF is resonant at 10.5kV 30mA. So you only want 11.25nF for LTR, that gives only a single string of 13 caps. I thought i should clear that up.
Very few coils use upwards of 25 of those MMC caps.
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Bulk buy
