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Re: mysterious coil failure / M and k Measurement (fwd)
---------- Forwarded message ----------
Date: Thu, 01 Nov 2007 00:33:25 +0200
From: Tomas Stankevic <Tomas.Stankevic@xxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: mysterious coil failure / M and k Measurement (fwd)
I have several glowing spots at the bottom of my 6" secondary. Should I
fix it? (Why?)
Tomas
Tesla list wrote:
> ---------- Forwarded message ----------
> Date: Wed, 31 Oct 2007 10:19:14 -0600
> From: resonance <resonance@xxxxxxxxxxxx>
> To: Tesla list <tesla@xxxxxxxxxx>
> Subject: Re: mysterious coil failure / M and k Measurement (fwd)
>
>
>
> We use an electric hot water heater element (about $5 at any local
> hardware). We always set our current at a steady 10 Amps and then read the
> milliVolts on the secondary. No changes in the reading and very accurate
> method.
>
> Dr. Resonance
>
> Resonance Research Corp.
> www.resonanceresearch.com
>
>
> ----- Original Message -----
> From: "Tesla list" <tesla@xxxxxxxxxx>
> To: <tesla@xxxxxxxxxx>
> Sent: Wednesday, October 31, 2007 8:25 AM
> Subject: Re: mysterious coil failure / M and k Measurement (fwd)
>
>
>
>> ---------- Forwarded message ----------
>> Date: Wed, 31 Oct 2007 07:02:14 +0100
>> From: Kurt Schraner <k.schraner@xxxxxxxxxxx>
>> To: Tesla list <tesla@xxxxxxxxxx>
>> Subject: Re: mysterious coil failure / M and k Measurement
>>
>> The safety concerns, regarding the circuit at Bart's site:
>> http://www.classictesla.com/download/M_and_k_Measurement.gif
>> can be eliminated, using a downstep transformer (i.e. Vout=6...12V; some
>> Amps), inserted between the mains AC line and the rest of the circuit. And
>> voltage may optionally be adjusted, by using a variac. This allows much
>> quicker measurement at different taps of the primary.
>> BTW, I'm also taking the measurements without the RC combination accross
>> the
>> secondary.
>>
>> Regards, Kurt
>>
>>
>> Tesla list wrote:
>>
>>> ---------- Forwarded message ----------
>>> Date: Mon, 29 Oct 2007 13:04:46 +0000
>>> From: "Lau, Gary" <Gary.Lau@xxxxxx>
>>> To: 'Tesla list' <tesla@xxxxxxxxxx>
>>> Subject: RE: mysterious coil failure (fwd)
>>>
>>> One doesn't need a signal generator or scope of any kind to measure
>>> coupling. You need only know the primary and secondary inductance,
>>> and perform the measurement described at
>>> http://www.classictesla.com/download/M_and_k_Measurement.gif
>>>
>>> I've not found it necessary to include the RC network across the
>>> secondary. The wording is confusing with "Take concentric readings
>>> from meters." I think what was meant is to take both primary current
>>> and secondary voltage measurements at the same time on separate
>>> meters.
>>>
>>> Regards, Gary Lau
>>> MA, USA
>>>
>>>
>>>> From: resonance <resonance@xxxxxxxxxxxx>
>>>> To: Tesla list <tesla@xxxxxxxxxx>
>>>> Subject: Re: mysterious coil failure (fwd)
>>>>
>>>>
>>>>
>>>> You need to check your coeff. of coupling and usually keep it below
>>>> 0.12 for most classic spark gap coils. Some of my coils run best
>>>> with greatest spark output at .08 to 0.1 range. A local Univ. or
>>>> tech college with a storage scope and sig gen can help you do this.
>>>> The equations and procedures are in the Tesla List Archives.
>>>>
>>>> If your coeff. of coupling is producing a "double hump" then your
>>>> coupling is too tight, energy is being wasted, and your coil will
>>>> hit HV peaks at two points --- sometimes not at the end of the sec.
>>>>
>>>> This produces tracking and eventually destruction of the coil.
>>>>
>>>> Also, be sure to always sand both interior and exterior of any
>>>> coilform prior to winding. Also use some small acrylic baffles
>>>> approx 6-8 inches down from each end in the sec. Silicone into
>>>> place with GE Silicone II --- available at most hardware stores.
>>>>
>>>> Dolph's AC-43 has much greater anti-tracking properties than
>>>> polyurethane, and it's price is reasonable if you consider the
>>>> amount of repair time that is required when a coil fails.
>>>>
>>>> Dr. Resonance
>>>>
>>>> Resonance Research Corp.
>>>> www.resonanceresearch.com
>>>>
>>>>
>>>> ----- Original Message -----
>>>> From: "Tesla list" <tesla@xxxxxxxxxx>
>>>> To: <tesla@xxxxxxxxxx>
>>>> Sent: Sunday, October 28, 2007 8:03 PM
>>>> Subject: RE: mysterious coil failure (fwd)
>>>>
>>>>
>>>>
>>>> ---------- Forwarded message ----------
>>>> Date: Sun, 28 Oct 2007 19:50:56 -0400
>>>> From: Scott Bogard <teslas-intern@xxxxxxxxxxx>
>>>> To: Tesla list <tesla@xxxxxxxxxx>
>>>> Subject: RE: mysterious coil failure (fwd)
>>>>
>>>>
>>>> Thanks guys,
>>>> I don't think it was a shorted turn, there is no carbon on the
>>>> inside but there is a tiny black spot on the outside (I don't use
>>>> end caps on my coils, is this bad?). I attach my RF ground by a
>>>> copper strap, soldered onto the end of the bottom turn, I think it
>>>> arced from the sharp edge of the strap to the wire above it (turn
>>>> 2). This occurred underneath of the several layers of electrical
>>>> tape coated with polyurethane insulation on the bottom. One other
>>>> detail I forgot to mention, I set the coupling as high as I could
>>>> get it that night to make up for decreased performance
>>>> from wind and humidity, so that may have contributed. I'll sand her
>>>> down and rewind the bottom and see if it works again, thanks guys.
>>>>
>>>> Scott Bogard.
>>>>
>>>>
>>>>> Date: Sun, 28 Oct 2007 11:07:40 -0700
>>>>> From: tesla@xxxxxxxxxx
>>>>> To: tesla@xxxxxxxxxx
>>>>> Subject: Re: mysterious coil failure (fwd)
>>>>>
>>>>>
>>>>> ---------- Forwarded message ----------
>>>>> Date: Sun, 28 Oct 2007 11:01:32 -0800
>>>>> From: Barton B. Anderson <bartb@xxxxxxxxxxxxxxxx>
>>>>> To: Tesla list <tesla@xxxxxxxxxx>
>>>>> Subject: Re: mysterious coil failure (fwd)
>>>>>
>>>>> Hi Scott,
>>>>>
>>>>> Yes, the glowing spot is either a shorted turn or carbon track. It
>>>>> may be a shorted turn and easy to fix if right on the bottom, and
>>>>> "if" it is like the very bottom turn, it's probably too much power
>>>>> for too long a period. I've had this happen on my 4" coil even with
>>>>> low coupling. If enough power is provided, it can cause extensive
>>>>> heating a greatest heating on the bottom of the secondary (highest
>>>>> current). If you were to continue running it, a nice little fire
>>>>> will begin. If it's a shorted turn, you'll have a nice black carbon
>>>>> ring around the entire turn. Real easy to fix obviously.
>>>>>
>>>>> Take care,
>>>>> Bart
>>>>>
>>>>> Tesla list wrote:
>>>>>
>>>>>> ---------- Forwarded message ----------
>>>>>> Date: Sat, 27 Oct 2007 22:10:06 -0400
>>>>>> From: Scott Bogard <teslas-intern@xxxxxxxxxxx>
>>>>>> To: tesla@xxxxxxxxxx
>>>>>> Subject: mysterious coil failure
>>>>>>
>>>>>>
>>>>>> Hey guys,
>>>>>> I was running my 6-in MOT coil tonight for my little cousins,
>>>>>> and it
>>>>>> died and I cannot figure out what is wrong. The spark gap fires
>>>>>> fine, I did not adjust anything, it just died between runs, and
>>>>>> won't arc except to a grounded rod (it acts like it is badly out
>>>>>> of tune, but like I said,
>>>>>> I adjusted nothing). The only thing different I notice, is that
>>>>>> there was
>>>>>> very high humidity, and I could see a tiny spark at the base of the
>>>>>> secondary. It isn't arcing to anything, it is just a glowing
>>>>>> spot, that melted through the electrical tape insulation. I'm
>>>>>> stumped, I guess I'll
>>>>>> tear the insulation off of the bottom of the sec' coil and see if
>>>>>> anything
>>>>>> is amiss, but I've never had a failure like this before. The only
>>>>>> other possibility is that somehow my ballast malfunctioned, but I
>>>>>> don't think so.
>>>>>>
>>>>>> Scott Bogard.
>>>>>>
>>>>>>
>>>>>>
>>>> _________________________________________________________________
>>>>
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>>>>>> Caf?. Stop by today.
>>>>>>
>>>>>>
>>>> http://www.cafemessenger.com/info/info_sweetstuff2.html?ocid=TXT_TAGLM_Oct
>>>> WLtagline
>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>>
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>>
>>
>>
>>
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