Re: Caps Question:

[Terry Fritz <twftesla-at-uswest-dot-net>]

At 03:09 AM 9/6/00 -0400, you wrote:
>Hi Terry!  Is this the proper way to get into the website when I have a ?
>about coiling?  If not please tell me how and I will rewrite this
>mailing.  

Yep, this is it!

>If it is correct, then, is there anyone on the list that could
>tell me if my doorknob caps would be rated for A.C or D.C. if there is no
>mention of it on the cap?  The people I got them from did not know the
>voltage type.  They are .004mf at 40kv.  So, is there any unwritten rule
>that will tell one what type of volts the device is rated for when there
>is no info on the cap? Reason I am asking is because I would like to use
>the 40kv caps as singles on my coil rather than doubling them up in
>series the way I have them now, but I don't want to fry them by learning
>the hard way that I did when I used a gang of hockey pucks which were
>15kv rated and stamped as D.C. volts on the shell.  It gets very
>expensive in a hurry when these caps fail.  

If they are new, you can tell be the price.  AC high Q door knobs are
really expensive.  Like $100+ each...  It is odd they are not marked  I
have a bunch of 30KV 1.72nF TDK caps that are about 1.5 inches in diameter
and 3/4+ inch thick.  If they look of very high quality and have heave
terminals they may indeed be nice high-Q types.  If anything on them looks
like rolled paper, they are definitely low-Q.

>I had the 15kv D.C. caps
>doubled up in series for a 30kv D.C. rating on my two 15kv -at- 60ma. neons
>and the caps still fried fairly quickly.  So should I just leave the good
>40kv caps doubled up as I have them now just to play it safe, because
>they appear to be indestructible when doubled. Has anyone else had
>experience with this kind of setup?    I know that M.M.C. cap banks seem
>to be the rage, but my luck with them was no good when I used them for a
>sustained 15 minute run.  Have any of you coilers had better luck than me
>with M.M.C. caps on extremely long runs?  Because those little M.M.C.
>scutters get real expensive too when the banks fry.  I have never had
>just one go bad, nosiree, they would short or open up in grand fashion
>and drove me nuts troubleshooting the banks looking for the culprits.   I
>would like to try the M.M.C.'s again but would like to hear from others
>first. Is there a really prime M.M.C. cap available that would go for
>say, at least possibly more than an hour with no damage that I could use
>on my yet to be built fourth coil?   Thank you,  Al.

MMCs will easily work but you have to use polypropylene pulse rated caps
and only run about 3 amps RMS through each string.  If they get fairly
warm, the current through them is too high and they will melt internally.
If you try MMCs again we can help with the details. 

>
>So many questions! So little time! 
>

Cheers,

	Terry