Re: [TCML] New 833C VTTC - poor performance

[futuret@xxxxxxx]

Kris,

You have to retune the primary as you increase the power
and as the sparks get longer.? A primary tune point that's best
for a 10" spark, will be the wrong tune point for a 20" spark.
This is because the length of the spark acts as an extra
capacitor and changes the resonant frequency of the secondary
while the spark is being produced.? You'll need to tune outward
on the primary, (use more turns), as the sparks get longer. 
This is most likely the problem you're having since I can't think
of any other good reason for the weak sparks and red tube plate
you're seeing.? 

20 turns on the grid coil is probably OK.? You can try tapping
off at 16 turns or so, but I doubt it will help.

Cheers,
John


-----Original Message-----
From: Kris Grillo <kristianisawesome@xxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sent: Fri, 1 Aug 2008 8:03 pm
Subject: Re: [TCML] New 833C VTTC - poor performance



John, list,

"I assume you have a breakout point above the toroid (about 4 to
5" tall or so maybe)"

I do have a breakout that extends 4" above the toroid.

"You have to tune at full power. If you tune at low power, the tune point will 
be wrong at high power."

I'm not sure what you mean by full power. I brought the variac up slowly until I 
noticed the plate glow, then I backed down a tad and made adjustments. I 
repeated this process for hours. Once I got the primary dialed in, I didn't mess 
with it at all. The power input couldn't change the frequency, could it? 

"I assume your caps can handle the power? Are they getting hot?"

As far as I know, they can handle the power. They are the TDK UHV-9A 202K 40KV. 
One for the tank and one for the grid leak. They were on again off again for 
quite a while and they do not even get warm as far as I could tell from 
occasional touch testing.

"Also if you have an 833A, you can try that."

I don't have one.

"You can try using a higher grid resistance too. Just put another resistor in 
series with the one you have."

I don't have an appropriate resistor on hand for this, but I will pick one up 
and give it a try.

Could 20 turns of #26 be yet to many turns for the feedback coil?  

Thanks, 

Kris











--- On Fri, 8/1/08, futuret@xxxxxxx <futuret@xxxxxxx> wrote:

> From: futuret@xxxxxxx <futuret@xxxxxxx>
> Subject: Re: [TCML] New 833C VTTC - poor performance
> To: tesla@xxxxxxxxxx
> Date: Friday, August 1, 2008, 7:28 PM
> Kris,
> 
> 
> 
> You're doing all the right types of adjustments.? I
> assume
> 
> you have a breakout point above the toroid (about 4 to
> 5" tall
> 
> or so maybe).?? Steve's coil is a good design.? It
> should work
> 
> well and give at least 22" sparks.? The tuning is
> quite critical
> 
> and all the adjustments are critical sometimes.? Here's
> what
> 
> the problem might be.? You have to tune at full power.? If
> 
> you tune at low power, the tune point will be wrong at high
> 
> power.? So you have to gradually work your way up to the 
>
 
> longer sparks, retuning and re-adjusting everything as you
> 
> increase the power and get longer sparks.? In other words.
> 
> Let's say the tube gets red at 8" sparks, then
> re-adjust so
> 
> it doesn't get red, but then it may get red at 10"
> sparks,
> 
> then re-adjust again, etc.? Takes awhile sometimes to
> 
> get a tube coil running right.? I assume your caps can
> 
> handle the power?? Are they getting hot??? Here's
> another
> possibility.? Did you verify that the tube pins are getting
> 10V while the filament is lit?? If the filament transformer
> gives 10V with no load (not connected to the tube), then 
> it might only give 8 or 9 volts under a load (connected
> to the filament.? I assume you checked all this but
> I figured I'd mention it.? It can take a long time to
> get
> a tube coil tuned up compared to a spark gap coil. 
> 
> Also if you have an 833A, you can try that.? It will show
> a red plate much sooner than the 833C, which can actually
> make it easier to tune the coil.? An 833C should not get
> red
> until the spark is over 22" or so.? You can try using
> a higher
> grid resistance too.? Just put another resistor in series
> with the one you have.? But the value you're using
> should
> be OK anyway I think.? 
> 
> Cheers,
> John
> 
> 
> _______________________________________________
> Tesla mailing list
> Tesla@xxxxxxxxxxxxxx
> http://www.pupman.com/mailman/listinfo/tesla


      
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