Re: VTTC Power Supply Fundamentals - What am I missing?

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Peter Terren" <pterren@xxxxxxxxxxxx>

You can't measure a half wave or a level shifted sine wave on a meter 
and expect to read the peak voltage - unless you use a diode in 
series and small capacitor in parallel then you should come close.
If you read them on an oscilloscope they would be fine under no load 
and you will see the voltage sagging under light load .
You can't draw much current off a multiplier.

Peter

----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Wednesday, October 19, 2005 6:52 AM
Subject: VTTC Power Supply Fundamentals - What am I missing?


> Original poster: "Chris Fanjoy" <zappyman@xxxxxxxxxxx>
>
>   Seems I've run into some tough problems with my VTTC power 
> supply. I've been using a large MOT, with a simple voltage doubler like this:
> ----------||-----------+----+------       B+
>                         |     |
>              ---->|---+     +--||--+
>             |                          |
> ------------+-------------------------+---   GND
>   Don't know how well that will display, but anyway....    So far 
> I've obtained about 8-9" sparks from the coil, which is driven by a 
> pair of 813 tubes. The sparks are very thick and hot, but it seemed 
> to me that they should be longer considering the input power. So I 
> connected a high-voltage meter (the type used for measuring CRT 
> voltage) to the power supply, and was surprised to see a reading of 
> only 2kV, even with no load. So I tried a different circuit:
> ---+----->|------+-----+-------
>    |               |      |
>    |               C1   C2
>    |               |      |
> -------------------+      |
>    |               |       |
>    |               C3   C4
>    |               |       |
>    +-----|<------+------+-------
>   Now, with no load, I measure a good 4kV. But, when the coil is 
> connected, it drops to less than half! What's more, the staccato 
> controller is seriously messed up, locking into continuous wave 
> when the variac is turned above roughly 20V.
>   The capacitors used for filtering are all microwave caps, 
> arranged in series/parallel combinations as the situation warrants. 
> Both circuits I've mentioned use 8 caps in all.
>   It seems I'm missing something here, but what? Why can't I keep 
> the supply voltage around 4kV? And why does the stupid staccato 
> controller keep acting up? The SC works great with the first 
> circuit. I should mention that the SC is mounted in an external 
> control box, which is connected via a shielded cable to the main unit.
>   Thanks for any help.