Re:Re: Caps Question:

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

Hi All,

	I was involved in the development of MMCs so all my research effort went
into that direction.  The doorknobs caps are still alive and well.  I still
use MMCs since they are so easy to adjust and I now have a number of coils
that require tight value caps.

	I run all my caps really hard in an effort to prove out MMC designs.  I go
over voltage and over current as standard practice.  However, it is easy to
conservatively design them too.  Much information is at:

http://users.better-dot-org/tfritz/site/MMCinfo/MMC.html
http://users.better-dot-org/tfritz/site/MMCinfo/MMCPower4.html

I can't say too much or your doorknobs.  If they are unmarked, they could
be anything...  All I can suggest is to try them and see if they blow up
which is not a great option...

Cheers,

	Terry



At 10:24 AM 9/6/00 -0400, you wrote:
>Thanks Terry!  It sounds as if you have tried the doorknob caps and
>traded them in so to speak for the mmc's.  What would be your principle
>reason for using the mmc's?  Better spark?  More Spark?  Why did you stop
>using the doorknobs?  It sounds like you are on to something that I have
>yet to get a grasp on, even with my previously bad experience with the
>mmc's.  Maybe I used the wrong types of caps and expected too much from
>them.  Will your mmc's take a sustained run?  There is not much more time
>to Halloween, and I need something good for a new fourth coil I am
>building. I need two good coils running simultaneously and cannot find
>any more 'good,cheap' doorknobs to fit my budget. I would need a minimum
>of 30 more ganged in series for my 4th coil.   That is why I wonder if I
>could use my existing 40kv doorknobs singly, so I could split up my
>supply of them.  They are 'new' caps and cost $25  each.  I have 30 of
>them.   Do you think that maybe that is why they cost so little and have
>no coherent A.C./D.C. markings?   Possibly seconds or fallouts?    They
>do work very well in series, but I am scared to try them singly unless I
>can somehow find if they are 40kv A.C. rated.  Although I may never
>really know.       Al
>
>
>On Tue, 05 Sep 2000 17:49:30 -0600 "Tesla list" <tesla-at-pupman-dot-com>
>writes:
>> Original poster: 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
>> 
>> 
>> 
>