Re: My PT is loud!

```Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>" <Tesla729-at-cs-dot-com>

In a message dated 2/21/01 7:15:10 AM Pacific Standard Time, tesla-at-pupman-dot-com
writes:

<< I
< noticed that if i got the capacitance way too high, and i turned up the
< variac to the pt, no sparks would jump the 1/2" saftey gap on the pt. It
< worked with a 16 wine bottle salt water cap! When i turned it up to around
< 60% A really loud buzzing/humming noise would come from either the PT or
the
< capacitor, which i have watched vibrate voilently before. It would stay
loud
< until i turned everything off. >>

Drew,

When you run your capacitor too large for the transformer, the transformer is
unable to fully charge the capactior within each half of the 60 Hz duty cycle.
This means that your tranformer sees the capacitor as an oversized load for
it, and basically a short. That, in addition to the fact that you are
inputting
nearly triple its rated input voltage, will definitely cause your
transformer's
core to saturate and hence, the loud 60 Hz. hum. Although PTs are built like
Ft. Knox, they are still not designed to be voltage overdriven this way and
you'll
probably eventually end up smoking it if you keep running it like this. The
ex-
ternal ballasting that you are using will probably keep it from being
seriously
overcurrented, but that 300 volts in where it's supposed to be 120V is
seriously
overvolting it and will likely shorten its life expectancy :-( As one of the
other
list members said, if it's rated at 120 volts input, you probably shouldn't
put in
over 140 to 160 volts, tops. I would try to get by with say, 150 volts in,
and that
would still give you over 5 kV output and then you could use those oversized
caps, since a lower voltage can charge a capacitor whose size (uFD) is
inverse-
ly proportionate to the square of the voltage ( If you half the voltage, the
cap size
must inreased four-fold to keep the same amount of energy).

Sparkin' in Memphis,
David Rieben

```