Re: [TCML] Burnt Joint (Cap Bank)

[Atomic <atomicrox@xxxxxxxxx>]

I'm no expert but I noticed your strike rail looks like a complete circle,
it should have a gap to avoid eddy currents sapping the coil's power.

Couple things you could test, in case it's working but a very low power:
-Add a breakout point
-See if it lights up a fluorescent lamp

On Mon, May 6, 2013 at 8:34 AM, Michael Gray <graymp89@xxxxxxxxx> wrote:

> Okay, I resoldered the cap bank board last night, and had another crack at
> running the TC this morning. Still doesn't work...!
>
> Just a quick run through of what I did: first I connected the safety spark
> gap directly across NST and adjusted so it was just wider than the NST
> could arc across. I then did the same for the main spark gap, except this
> time a tiny bit narrower than max. Then checked all connections with
> continuity tester and checked the wiring was correct. Here's a pic of my
> circuit diagram:
>
> http://imageshack.us/photo/my-images/211/20130504191918.jpg/
>
> Then I fired it up (variac was connected but I just had it on 100%), and
> the main spark gap was going, very bright with a loud crackling sound which
> I presume is about right. But the toroid wasn't doing anything. I left it
> running like that for about 10 - 20 seconds and still nothing, so I
> switched it off to investigate.
>
> Disconnected everything and re-tuned the spark gaps as described above.
> Then connected the NST across the Terry filter, with the other end of the
> Terry filter left open, and powered up - no sparks on safety gap (as
> expected). Moved on to connect Terry filter up to the main spark gap,
> powered up and the spark gap was arcing much quieter and continuously (as
> expected). Then connected one end of the spark gap to one end of the
> capacitor bank, with other end of cap bank left open, powered up and spark
> gap continued to arc the same as before (as expected). Then connected the
> other end of the spark gap to the base (inside most) tap point of the
> primary, powered up and spark gap continued arcing as before (as expected).
> Just to be thorough, I then disconnected the spark gap from the primary and
> instead connected the other end of the capacitor bank to the outer tap
> point on the primary, powered up and spark gap again arced as before (as
> expected). So up until now everything seemed okay, until I completed the
> circuit by connecting the spark gap to the primary again. On powering up,
> the spark gap this time was arcing as I described earlier, i.e. much
> brighter with a very loud crackling noise (as expected), but the toroid
> wasn't up to much, in fact nothing whatsoever. I was quite disappointed to
> be honest...!
>
> Anyway I've taken a load of pictures of it (below), does anyone have any
> ideas?
>
> http://imageshack.us/photo/my-images/51/20130506121432.jpg/
> http://imageshack.us/photo/my-images/138/20130506113409.jpg/
> http://imageshack.us/photo/my-images/194/20130506113502.jpg/
> http://imageshack.us/photo/my-images/199/20130506113443.jpg/
> http://imageshack.us/photo/my-images/545/20130506113418.jpg/
> http://imageshack.us/photo/my-images/405/20130506113427.jpg/
> http://imageshack.us/photo/my-images/12/20130506113343.jpg/
>
>
> On 5 May 2013 21:56, Michael Gray <graymp89@xxxxxxxxx> wrote:
>
> > Thanks for the advice everyone. I must have forgotten to include the
> > bleeder resistors. This board is the second iteration of my cap bank; the
> > first had bleeder resistors on it so I must have forgotten to include
> them
> > on this one. So I'm resoldering it completely, removing the red wiring
> > between each cap and replacing with the legs of the resistors as they are
> > long enough to adjoin each cap too. Good point about the trailing leads -
> > I've now tied each trailing lead to the board with some magnet wire,
> > through the board holes and twisted taught.
> >
> > When I first turned on the coil I did here what sounded like arcing as I
> > was turning up the variac (before spark gap had fired), but I wasn't sure
> > what it was as I couldn't see the cap bank from where I was standing, and
> > of course it was my first go so I didn't know what to expect. So that was
> > probably the dry solder joint as has been suggested. I'll hopefully have
> > the board resoldered tonight, and will have another crack at it in the
> > morning. Hopefully it works, very excited, thanks everyone!
> >
> >
> > On 5 May 2013 08:54, Phil Tuck <phil@xxxxxxxxxxx> wrote:
> >
> >> Michael,
> >> You need to physically anchor all of those 12 red 'trailing leads' to
> the
> >> board. Either by wrapping some wire around the lead itself and then
> >> through
> >> the board's holes, close to the edge of the board, or a spot of 'Hot
> Glue'
> >> to tack them to the board. Otherwise they are relying on the soldered
> >> connections everytime the leads move or flex.
> >> The original trouble, as the others say, was a 'dry joint' (solder not
> >> properly melting onto the wire, or only being held there by the resin in
> >> the
> >> solder)
> >> I have used that board to mount a string of diodes once, to rectify
> 10kV,
> >> and the board ending up tracking. I had to put it under oil to allow it
> to
> >> work (it was just a temporay test setup anyway).
> >>
> >> Regards
> >> Phil Tuck
> >>
> >> www.hvtesla.com
> >>
> >> -----Original Message-----
> >> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> >> Behalf
> >> Of Michael Gray
> >> Sent: 04 May 2013 22:05
> >> To: Tesla Coil Mailing List
> >> Subject: [TCML] Burnt Joint (Cap Bank)
> >>
> >> I fired up my (first) TC for the first time today, after months of
> putting
> >> everything together. Needless to say, it didn't work! I was slowly
> turning
> >> up the variac, the spark gap fired up, and then I saw some smoke coming
> >> from the cap bank. So I powered down and investigated - turns out one of
> >> the soldered joints had smoked. I kinda regret buying the caps I did,
> the
> >> legs on them are tiny and this makes it difficult to string them
> together.
> >> The caps are mounted on some Vector prototyping board, and because the
> >> legs
> >> are so small I've had to solder a very small length of high voltage wire
> >> between each cap. I'm looking for some advice really on my cap bank - is
> >> soldering prone to burning out like this? What's the best way to make
> the
> >> connection? Should I try to solder the legs directly together instead of
> >> using an adjoining length of wire? Should I invest in different caps?
> >>
> >> The caps are rated at 0.047uF at 2kV:
> >>
> >>
> http://uk.mouser.com/ProductDetail/Kemet/PHE450SD5470JR06L2/?qs=s4t14sB06yQT
> >> V0lacTv0rw==
> >>
> >> In 6 strings of 10 their total capacitance should be in the region of
> >> 28.2nF.
> >>
> >> Here are a couple of pictures of it, you can see the burnt out joint on
> >> the
> >> right:
> >>
> >> http://imageshack.us/photo/my-images/841/20130504212930.jpg/
> >> http://imageshack.us/photo/my-images/713/20130504212952.jpg/
> >> _______________________________________________
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> >>
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> >
> >
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