Re: SSTC probs

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "S.Gaeta by way of Terry Fritz <twftesla-at-qwest-dot-net>" <sgtporky-at-prodigy-dot-net>

Hi Matt,

I am no expert on MOSFET coils, but I am a ham and have repaired a lot of
rigs that have blown due to people not connecting them to a resonant
antenna. When you get into solid state stuff, resonance becomes very
important. If the secondary is not in tune, the power is reflected back into
the MOSFETS instead of going into streamers, causing them to go POP! The
oscillator will tend to draw a lot more input current if things are not
resonant also. Try and get the system tuned before changing the devices,
even if it means pushing the solid state stuff aside, and temporarily
connecting an NST and static gap to the primary at low power just to find
the right tap point to at least get close to resonance. I am sure that this
is not the only problem since MOSFETS are finicky little devices, but this
is a good place to start.

Good luck,
Sue
----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Thursday, November 22, 2001 12:34 PM
Subject: SSTC probs


> Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<Fucian-at-aol-dot-com>
>
> Hi guys, this is for the SSTC experts.Ive been using a simple 555 timer
and
> IRF740 MOSFET to run a true tesla coil secondary.I get pretty good output
for
> the fact its way out of tune.My input power is a 4.5amp variac.When I try
to
> go abouve maybe 70 volts, the MOSFET makes a small little pop noise and
> output goes to zip...WHY?Ive killed maybe 10 now!Whats happening?Ive got a
> 150amp 1200volt hyperfast diode on the output to the coil.Anode towards
the
> MOSFET and cathode to the coil.I also have another identical diode going
> across the source and drain.They both get a little warm.The MOSFET is on a
> fan cooled heatsink.It gets really hot.
>
> Matt
>
>
>