Re: [TCML] Odd VTTC Streamer Behavior

["Phillip Slawinski" <pslawinski@xxxxxxxxx>]

I'm running a 2nF 12kV Mica transmitting cap.  As I can recall the coil has
always misbehaved above 105-120V.  The streamers still have that thudding,
but it's snappier like you said.  Of course this is in stacatto mode, and
I've tried adjusting the controller to no avail.  I did sharpen my breakout
point which helped a considerable amount, but I'm still two and a half
inches from where I was before. [That's a 7.35% decrease, which is
statistically signifigant.]  I think the lackluster performance can be
pinned on the changes I made to the primary.  When I was getting 34" hits
consistently I had unraveled my 28 turn primary by a about five turns, but I
did not remove the extra wire, I had it coiled hanging over the side of the
VTTC enclosure.  When I decided to tidy this up I removed a little of the
wire, wrapped the rest around the form, glued it in place, and then added
taps.

I sure hope my tank cap is not going bad, the last thing I need is another
stain on the carpet.

On Mon, Oct 20, 2008 at 22:50, Dr. John W. Gudenas <comsciprof@xxxxxxxxxxxxx
> wrote:

> Phillip
> I ran into a problem like this and it was associated with the tank
> capacitor starting to fail.
> If I increased the voltage after about 95volts the streamers got smaller
> and "snarpy".
> I wasn't running a staccato controller so like John F. said something was
> going bad.
>
> While not a good idea, in complete frustration, I cranked up the variac and
> waited for something to fail.
> I exploded a mica transmitting cap. Nasty mess. If you are running an MMC,
> after a run see if they are getting warm.
> All it takes is one bad cap in an MMC.  If your coil was running great,
> then it started to run not so great and you didn't change a thing,
> you likely have a failing component or poor connection somewhere. In my
> case it was the tank cap.
> Yours could be different. Good Luck
> John
>
> John W. Gudenas, Ph.D.
> Professor of Computer Science
>
>
>
> On Oct 20, 2008, at 9:28 PM, Phillip Slawinski wrote:
>
>  I ran it for quite a while today, and I think I made some progress towards
>> getting back to where it used to be.  It's hitting 31.5", and it's making
>> a
>> thudding sound while doing so.  It does this while running just shy of
>> 105V.  If I push it up to 115V or higher the sparks start to make a
>> cracking
>> sound in addition the the thudding.  It's also at this point that the
>> sparks
>> start to branch and become shorter.
>>
>> I tried lowering grid resistance and it only results in shorter sparks,
>> and
>> only marginally at that.  I'm a little wary to lower the resistance since
>> the accident that marked the end of the good performance I was getting
>> from
>> the coil.  I kept turning down the resistance until the secondary flashed
>> through the silicone sealant and ruined my grid coil.  Of course, this was
>> an extreme case, and foolish at that.
>>
>> I did move the grid coil down to increase the coupling a little and that
>> seemed to help.
>>
>> On Mon, Oct 20, 2008 at 21:03, <futuret@xxxxxxx> wrote:
>>
>>  The throaty popping sound may be a "bad" sound meaning
>>> the coil is not running just right.  Some component may be
>>> failing.  Or the staccato controller timing may have changed
>>> in some way.  The solid thud sound is good, other types
>>> of sounds can be bad.  Is it a raspy sound?  If so that's
>>> a sure sign something isn't right.  Maybe from the high
>>> power operation of the tubes, they became damaged.
>>> Or arcing may have been occuring in the tubes which
>>> can make a popping sound.  You can try reducing the
>>> grid resistance to see if it helps.  That tends to keep
>>> the voltages in the tube lower and may help.  But it
>>> will make the tubes run hotter of course.  But it may
>>> be helpful just as a quick test to get an idea of what's
>>> happening.
>>>
>>> John
>>>
>>>
>>> ---
>>>
>>
>
>
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