RE: [TCML] Help with high school Tesla coil

["Arnold, Mike" <marnold@xxxxxxxxxxxxxxxxxxxxxxxx>]

Thanks for your help, John. I know the students enjoy the Tesla coil and 
 I want to get it working again. Some of the students even seem to 
 understand its mysteries :^)
 
 I've posted more images at http://collierhighschool.com/tesla/  If you 
 need closeups of specific components, I would be happy to take more photos.
 
 I will try to get my hands on a scope, but I'm a little doubtful I will 
 be successful.
 
 I do still think it has something to do with the timer not shutting 
 off.  It still fires sparks off.  I've included a photo of the dial for 
 the timer and, when I turn the dial, it feels a little funky.
 
 I don't want to blow up expensive components in the process of trying to 
 fix it so I look forward to hearing your thoughts.
 
 thanks very much,
 
 Mike

-----Original Message-----
From: tesla-bounces@xxxxxxxxxx on behalf of John Forcina
Sent: Wed 11/11/2009 1:18 PM
To: Tesla Coil Mailing List
Subject: Re: [TCML] Help with high school Tesla coil
 
Hi, It looks like that is a drsstc and not a standard sstc.  We are going to
need some more info on your coil in order to help you.  Can you post some
pictures of the driver board along with the H bridge board and the dials of
the remote control.  Your problem could be a number of reasons but for now
im going to list some obvious ones.  You might have your "ON" time or duty
cycle set very high meaning the coil will pull much more power then if it's
set to a low duty cycle and you risk blowing your igbt's.  Another thing i
can think of is the shootthrough on your igbt gates causing one igbt to turn
on before the other is completly shut off and this will act as a direct
short across your supply rails for a very short time.  By any chance do you
have or does your school have a scope that you have access to because that
will make debugging much easier.

John.

On Wed, Nov 11, 2009 at 10:02 AM, Arnold, Mike <
marnold@xxxxxxxxxxxxxxxxxxxxxxxx> wrote:

> Our school has a solid state Tesla coil. I am attempting to get it into
> working condition. It had a bad solder connection in the tuning remote
> control. I have repaired the bad connection.
>
> Now the coil will spark for 1 or 2 seconds and then it trips the 20amp
> circuit breaker. The coil only works (albeit briefly) if the burst rate
> is high and the timing is high. The power cable gets warm in those
> couple of seconds. (Not to influence responses, but I'm not positive
> that the timing is working. It seems like the sparks burst without pause
> -- da-da-da-da-da -- until the circuit breaks. I can definitely slow th
> e rate -- da----da----da-----da.  I can see the pot for the timing and
> it looks like it might have some cold solder joints.)
>
> When hooked up by itself, the low voltage transformer that powers the
> control board does not blow the fuse.
>
> A photo of the board can be seen at
> http://collierhighschool.com/teslacoil/board.jpg and I can provide more
> photos if it helps.
>
> Any help would be appreciated.
>
> Thanks,
>
> Mike
> _______________________________________________
> Tesla mailing list
> Tesla@xxxxxxxxxx
> http://www.pupman.com/mailman/listinfo/tesla
>
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